To David Christian

Foreword

by John Green

Humans like a good story and, since we are as a species somewhat narcissistic, we’re especially fond of the story of ourselves—how we came to be here and why. These days, we call that story history, but for too long we’ve had a narrow definition of history, one that dramatically distorts reality.

As a high school student, I was taught that “recorded history” began about 5,000 years ago, with the invention of writing. However, that definition leaves out almost all of the human story—at least 95 percent of it. Of course, we cannot know the humans of 100,000 years ago as intimately as we know Genghis Khan or Cleopatra but omitting them from the story makes the human story seem much newer than it actually is. When you imagine that our story begins with the emergence of agriculture, or writing, or any particular innovation, the human story seems to look like an ascending line: lives get longer. People grow less hungry, and less poor, and more educated. Technological improvements are shared more widely, and innovations pile upon innovations to ensure that life inevitably improves.

For most of human history, that wasn’t really the story. Important innovations were made, as small communities passed down knowledge from one generation to the next, but human lives have not always grown consistently healthier or more productive. As you will learn in this book, we nearly went extinct long before we figured out how to develop agriculture or steam engines or antibiotics. We have been the dominant species on this planet for the briefest flicker of our history, and until we understand that, we can’t reckon meaningfully with the dramatic and sudden changes we’re making to our planet and its biosphere.

Narrow views of history also too often create a false dichotomy between the “hard” sciences—chemistry, physics, biology—and the “soft” humanities—history and literature and anthropology. Human stories cannot be viewed in isolation—we can’t understand fourteenth-century Europe without learning about the biology of Yersinia pestis and the rats that carried it. And we can’t understand how life came to be on Earth without glimpsing how time began in the first place, and how each of us is made from stars.

In The Shortest History of Our Universe, David Baker introduces us not only to the history of our species and our planet but also to the history of our vast universe. We are not the end of that story, nor its beginning—instead, we have emerged in the middle of a tale that will continue long after we are gone. Glimpsing the breadth of the universe’s history can make a person, or a species, feel very small indeed. And yet it is also a reminder of how wondrous life is, and how astonishing. As Baker writes, when we look into the night sky, we are not looking at the Universe, we are the Universe looking at itself.

John Green is the New York Times–bestselling author of Looking for Alaska, An Abundance of Katherines, Paper Towns, The Fault in Our Stars, Turtles All the Way Down, and The Anthropocene Reviewed.

Introduction

This book follows the continuum of historical change of all the “stuff” in the cosmos, from the Big Bang to the evolution of life to human history, as simple clumps of hydrogen gas are transformed into complex human societies. History allows us to live many lives instead of just one, and this particular story instills in us the combined experience of billions of years. Much confusion over human identity, our philosophies, and our future could be resolved if only the average person knew the key beats of the “story of everything” at least as well as they knew the key moments of their national histories.

Zooming out to take a bird’s eye view of 13.8 billion years allows us to see beyond the chaos of human affairs to the overall shape and trajectory of history. The thread that runs through the entire grand narrative is the rise of complexity in the cosmos, from the first atoms to the first life to humans and the things we have made. It allows us to traverse eons without drowning in detail—because the amount of detail an answer requires depends on the nature of the question. In this book, we ask simply: Where did we come from and where are we going?

Regarding the future, I am speaking in terms of the next hundred years, the next thousand, the next million, the next billion and even the next trillion, to quadrillion, to the potential end of the Universe. The Shortest History of Our Universe explores all that too.

For the science-phobic, rest assured there will be no math equations, and foreign cosmic phenomena will be boiled down to plain speech. For the history buff, humans may occupy only what a colleague called the “thinnest chip of paint at the top of the Eiffel Tower” of 13.8 billion years, but for very real, objective reasons humans occupy a very important role in the story. As far as we know, human societies and technologies are thus far the most complex structures in the entire Universe. We are a tightly woven web of 8 billion whirring brains, each with more nodes and connections than there are stars in the Milky Way. The next rise of complexity is likely to come from us—or at least something like us that evolved elsewhere in the cosmos.

French historian Fernand Braudel once likened the political events of recent history to bubbles and swirling foam atop an ocean of deep time. Here today, gone tomorrow. To truly understand where we are and where we are going, we must look below to the deeper currents and tides. The tendency of complexity to increase in the Universe moves the entire historical ocean. This trend toward rising complexity created us and continues to change us. Astoundingly, a self-aware humanity currently has the power to control where complexity goes next.

Our past can be divided into three phases.

• The Inanimate Phase: 13.8 billion to 3.8 billion years ago

• The Animate Phase: 3.8 billion to 315,000 years ago

• The Cultural Phase: 315,000 years ago to the present

Each phase corresponds to a major increase in complexity. The Inanimate Phase covers the non-living cosmos from the Big Bang to the formation of the Earth. The Animate Phase starts with the first microscopic life at the bottom of Earth’s oceans and sees the evolution of billions of complex species and ecosystems. The Cultural Phase begins with the ability of humans to accumulate more knowledge and develop tools and technologies over a short period of time, drastically changing how we behave and live despite the fact our biology has not changed much. In each phase, complexity drastically increases: from the grinding crash and thunder of the cosmos, to generations of evolution by natural selection, to cultural evolution or collective learning. The pace of historical change also accelerates rapidly: Cosmic changes can take billions of years and evolutionary changes millions of years, whereas cultural changes are measured in millennia, centuries, years—even days.

Every shift in complexity, each major event of the past, every newly emerged form of evolution builds on what came before it. Our story also has a fourth phase—the Unknown, in which complexity will leap forward yet again and set off an entirely new stage of cosmic evolution and historical change. Perhaps humans will give way to the accelerated creation and innovation powers of self-aware AI (artificial intelligence). Perhaps humans will upload their consciousness to computers and travel across the galaxy. Perhaps quantum physics will allow unprecedented manipulation of the building blocks and fundamental laws of the Universe. All we know for certain is that unless complexity is outright destroyed, some sort of increase in complexity is only a matter of time. And in the human realm, the changes keep coming faster and faster.

The generations of humans alive today occupy a pivotal role in a story that has been unfolding for 13.8 billion years. By understanding the long-term story from billions of years ago, we are better placed to make long-term plans billions of years into the future.

part one

The Inanimate Phase
13.8–3.8 billion years ago

chapter 1

The Big Bang

Wherein all the “stuff” in the Universe appears • Space appears to give us somewhere to put all that “stuff” • Time appears and makes it possible for that “stuff” to change form (i.e., have a history) • All that “stuff” is primordial energy and matter that transforms into the diverse range of things around us

Bang.

About 13.8 billion years ago, a tiny, hot, white speck appeared. It was so small that at first it could not have been seen by the naked eye or anything except the most powerful of modern microscopes, had they existed.

This was the appearance of the space-time continuum and the extremely hot, densely packed energy within it. Nothing existed outside of it. All the ingredients for everything in the Universe were within it. They have simply changed form since then, as if the Universe were a ball of clay, shaped and reshaped into myriad forms over billions of years.

The absolute first date in all of history is 10–43 seconds after the Big Bang, or 1.0 with the decimal place moved to the left forty-three times:

0.0000000000000000000000000000000000000000001

A tiny sliver of a second. It is the smallest possible chunk of time that we can measure. A smaller fraction of time would be physically meaningless, because nothing in the Universe can move fast enough to show that even the slightest change has happened in a smaller amount of time. 10–43 seconds is the amount of time it takes for light to travel the smallest amount of distance at the quantum level. Any smaller snapshot of time (for instance, 10–50 seconds) looks exactly the same as 10–43 seconds. It is like the first frame of a film.

The Universe was smaller than an atom or even one of the particles that make up that atom. Because of the pressure of everything in the Universe being contained within that small space, it was incredibly hot. Up to 142,000,000,000,000,000,000,000,000,000,000 Kelvin or 142 nonillion (so hot it is practically the same in both Celsius and Fahrenheit). The laws of physics themselves could not stay coherent. The Universe was so hot that the very laws that make it work were in a “melted” form. It was true, unadulterated chaos. Alice in Wonderland and a pint of LSD.

A tiny fragment of a second later by 10–35 seconds after the Big Bang, the Universe had expanded to the size of a grapefruit. It would have become visible to the naked eye. It cooled below 11.3 octillion Kelvin. This was cool enough for the four fundamental forces of physics to “harden” into their current form. Gravity, electromagnetism, and the strong and weak nuclear forces became coherent. We were now a Universe governed by physical laws. If they had hardened into a slightly different balance, the Universe would have evolved completely differently.

During this time, a ripple at the quantum level made tiny pinpricks of energy clump together. Energy in the Universe was just ever so slightly unequally distributed. These clumps of energy would evolve into all the matter, complexity, stars, planets, animals, and “stuff” in the Universe, including you.

By 10–32 seconds after the Big Bang, the Universe was about 3 feet (1 m) wide, and the heavy lifting was over. The clock was wound, its mechanisms were set in motion and it began to tick. In the first split second, our destiny was already etched into the very fabric of the cosmos. And the rest, as they say, is history.

For the next 10 seconds, the Universe grew to 10 light-years wide, swirling with tiny particles that had congealed from pure energy as the Universe continued to cool to 5 billion Kelvin. They were quarks and anti-quarks, positrons and electrons. The opposites of each other. Matter and antimatter. Much of the matter bumped into the antimatter and exploded in a flash, turning back into energy. Only one-billionth of the matter could not find an antimatter partner, and it is only this tiny fraction of matter that forms all the “stuff” in the Universe we see today. Here, within the first 10 seconds of the story, is a miracle that saved us from non-existence.

Over the next three minutes, the Universe continued to expand. It was over 1,000 light-years wide: a sea dominated by thick, merciless radiation. The surviving quarks were forged together by the still-intense heat into protons and neutrons. These protons and neutrons were in turn forged into the core of hydrogen and helium atoms (the nucleus). Hydrogen and helium were the simplest and first of all the elements to exist. Hydrogen requires only a single proton as its nucleus. Helium requires more ingredients and was therefore in the minority. The Universe cooled below 100 million Kelvin—too quickly for many of the other elements to be created (only trace amounts of lithium and beryllium). Heavier elements would have to wait for the creation of stars many millions of years later.

The Universe continued to expand and cool for thousands of years, longer than Homo sapiens has existed. By 380,000 years after the Big Bang, the Universe was over 10 million light-years wide and it had cooled to 3,000 Kelvin—twice as hot as lava and enough to melt gold or cause a diamond to drip like an ice cube on a summer’s day. The heat was still enough to obliterate most complexity, but it was cool enough for hydrogen and helium nuclei to capture electrons and become full-fledged atoms. The Universe began to fill with clouds of gas.

The Universe had also become less dense, allowing photons of light to travel freely through the thick soup of radiation and particles for the first time. There was a blinding flash of light, as these photons headed in every conceivable direction. This flash of light is known as the cosmic microwave background (CMB) and can be detected in every direction in the Universe today. In fact, if you set your radio or TV to collect only static, about 1 percent of that static will be from the CMB. It is the first baby picture of the Universe and the first visible artifact of our deep past.

How Do We Know the Big Bang Happened?

We know the Big Bang happened for several reasons. For starters, we can’t find anything in the Universe—either on Earth or through a telescope—that is confirmed to be older than 13.8 billion years old, which is the current estimated age of the Universe. If the Universe was infinite and eternal, we’d be tripping over stuff that was 105 billion or 802 trillion years old.

Second, the fact that normal matter in our Universe is mostly hydrogen and helium is exactly what you’d expect to see if the expanding Universe was super-hot for a few brief minutes but then cooled down quickly without time for many heavier elements to form. Again, if the Universe was infinitely old and infinitely big, we’d have no clear explanation why the chemical composition of the Universe is the way it is. In an infinite Universe with an eternity of stars blowing up in supernovas, there would be no clear reason not to expect just as much gold to exist in the Universe as hydrogen.

Third, in the 1920s Edwin Hubble was mapping the cosmos and discovered that most galaxies are heading away from us as space expands. Logically extrapolating from that, and calculating backward, Hubble figured out that all the galaxies in the Universe must have been smooshed together at a single fixed point. Despite this discovery, the Big Bang theory was not the dominant theory of cosmology for decades. Which leads us to the fourth and most crucial piece of evidence: the cosmic microwave background that emerged 380,000 years after the Big Bang. If the Big Bang theory were true, then after a few thousand years of the Universe expanding, the crush of matter and plasma and radiation would be spread out enough for light to be able to travel freely, and there would be a brilliant flash across the cosmos. In the 1940s, physicists predicted we should be able to see the remnants of this flash everywhere in the sky. This is precisely what was discovered in 1964 by two radio engineers, Arno Penzias and Robert Wilson, who weren’t even looking for it. They were trying to eliminate all the static on a highly sensitive radio antenna, but they couldn’t get rid of a small hiss, and after many calibrations, and having shot the pigeons that shat on the antenna, a physicist from Princeton told them what they had found. From that point on, the Big Bang became the dominant explanation for the start of the Universe and all the work that has happened since has only confirmed or clarified the general framework of this theory.

What Does the Universe Look Like?

In the first split second after the Big Bang, the Universe inflated from the size of a quantum particle to that of a grapefruit. Within a second, it was larger than our solar system. Four years later, it was bigger than the Milky Way.

The Universe, as we know it, is currently 93 billion light-years across. Which means there are stars and galaxies that were born billions of years ago that are so far away their light hasn’t had a chance to reach us, since only 13.8 billion years have elapsed since the start of the Universe. The stuff we can see looking out from Earth is called the Observable Universe, but there are a lot of things beyond that horizon that we cannot see.

Moreover, because light takes time to travel from a distant object, the farther away we look, the farther we are looking into the past. For instance, a neighboring galaxy, Andromeda, is 2 million light-years away. So when you look at it through a telescope, you are seeing it as it existed roughly when Homo erectus started roaming the Earth and saber-toothed tigers were still a cause for concern.

The Observable Universe can be seen looking in any direction from Earth; in that sense, the Observable Universe is a sphere. However, that is not the shape of the entire Universe. Physicists have determined that the Universe has “zero curvature,” which means it does not bend back on itself at some point. It stretches on and on, like a tabletop in any direction, constantly expanding for all eternity. The Observable Universe is just one patch on it: like the ring left by a coffee cup on a table. And Earth is just one tiny fiber of wood lodged somewhere inside that coffee ring.

Cosmic microwave background (CMB)

The color of the Universe is beige, assuming we were looking at the entire Universe from a great distance with human eyes. If you were to look at the mixture of light from all the stars in the Observable Universe blended together, as if you were zoomed out and looking at the whole thing at once, the color of our cosmic bubble would be beige. Cosmologists have tried to jazz it up by calling the tone “cosmic latte,” but it’s really just beige. Personally, I like the fact the Universe is beige; it renders the cosmos slightly less intimidating.

What Is the Multiverse?

Permit me to get a little weird for a moment. One inevitable consequence of the Big Bang model (the most accepted model currently) is a phenomenon called “eternal inflation,” which means that while our coffee ring of the Observable Universe has popped out of inflation and is expanding more slowly than in the first split second, other parts of the tabletop may still be expanding at that speed. And there will be other coffee rings (that is, other so-called universes) with physical laws and variations in historical events entirely different from our own. And this process would stretch on forever. This collection of diverse “universes,” each roughly the size of our Observable Universe, is known as the Multiverse.

But the term Multiverse is a misnomer: It’s all the same Universe, just different patches or coffee stains on the table, with different physics. There are an almost infinite number of variations of physical laws (10⁵⁰⁰ or nearly six times the number of atoms in the Observable Universe), and each one of those sets of physical laws could yield many different historical results. This means—if the hypothesis is true—there is another “universe” out there where you are reading this sentence 1.5 seconds earlier. There is another universe where you were not born at all. There is yet another universe where no stars exist. There is a universe where World War II didn’t happen. And one where your face looks like cotton candy and the sidewalk looks like pizza. Every possible variation you could imagine and quite a bit more besides.

If this hypothesis is true, we should be able to confirm it once the light from the nearest other “universes” that have appeared (if they have such a thing as light) finally reaches us . . .

. . . in about 3 trillion years.

How Can We Understand the Big Bang?

If trying to understand how our Universe began gives you an existential headache, it’s not your fault. Humans evolved within an older Universe with fixed rules, as did our brains and perceptions, so it is not so easy for our brains to grasp an event that precedes the establishment of the physics we have intuitively come to know. We are evolved to instinctually understand the world enough in order for our species to survive: What goes up must come down, cause and effect, chickens come from eggs and eggs from chickens. The rest takes a bit more time and reflection.

Imagine a speck. A tiny speck. This is the Big Bang singularity 13.8 billion years ago at 10–43 seconds. All energy and matter were contained within that speck. All the ingredients for the rest of our story. But whatever you do, don’t imagine that there is space outside the speck. Space is a property of our Universe and exists entirely inside it. As the Universe expands, more space is created. Don’t even imagine pitch blackness outside the speck, like we see at night between the stars. That is space. At the moment of the Big Bang there was nothing but the speck.

In fact, get a piece of paper and a pen and draw a tiny dot in the middle of the paper. Then take a pair of scissors and cut off all the extra paper outside the dot. That is the early Universe. The primordial atom containing all of time, space and energy, which has grown into the tabletop that is still expanding today.

What Happened Before the Big Bang?

Time didn’t exist before the Big Bang; thus, there was no “before” the Big Bang. It would be like claiming you introduced your mother and father to each other: nonsensical.

Space also did not exist before the Big Bang. “Before” the Big Bang, there was no space for anything to happen and there wasn’t any time for it to happen either. After the Big Bang, the Universe expanded from the microscopic to its current size of 93 billion light-years across (and growing). Space is a post–Big Bang phenomenon. Time is post–Big Bang too. “Before” the Big Bang, if there is no space for anything to move, there is no space for anything to change. And if there is no change, there are no events, and no history. Nothing that could be measured by time in any meaningful way.

So “before” the Big Bang there was no space, no change, and no “stuff” that moved or was transformed. Nada, zip, zilch. If anything existed prior to the Big Bang, it would have behaved in a way completely foreign to humans, and to the fundamental laws of the Universe itself as we now know it. It would not have behaved in a sequence of cause and effect—of past, present, and future.

Hence, our history begins with the Big Bang.

How Do You Get Something from Nothing?

There’s a deeply ingrained bit of human logic that says: If you create something, its building blocks have to come from somewhere else. This is what the First Law of Thermodynamics boils down to: Matter and energy are neither created nor destroyed, they simply change form. Yet the Universe seems to have appeared out of nowhere.

But at the moment of the Big Bang, the Universe was so insanely hot (142 nonillion Kelvin), its physical laws did not yet exist. This includes the First Law and the general notion that something has to come from somewhere.

Furthermore, the Big Bang at 10–43 seconds was so small it was at the quantum scale. Things operate differently in the quantum realm. Little ripples of energy known as virtual particles appear and disappear at that scale all the time. They are currently doing so in between the atoms that form your skin. Popping in and out of existence as if from nowhere. And this is established physics within our Universe, so “something from nothing” is not really so unthinkable a proposition for the start of the cosmos. Perhaps our Universe emerged in a similar way to virtual particles.

There’s also the consideration that before the existence of time, you don’t have the traditional sequence of cause-and-effect with which humans have evolved and expect to see. There is no physical law obliging the Universe to have emerged from something else.

And further still, we humans don’t really know what nothing is—beyond the meanings we ourselves have invented. As a shorthand expression, “nothing” means the absence of something specific. The concept of nothing works in the context of I have “nothing” in my pint glass and “nothing” in my wallet to buy another beer. Within true blue physics, however, it is impossible for “absolutely nothing” to exist anywhere in the Universe—even in the deepest regions of space. Everywhere the Universe either has “stuff” like stars and planets and gas or at the very least the weak hum of radiation. Your wallet may not have money in it, but it has air, a debit card, some old ticket stubs, dust, and perhaps even a dead fly. Scientists can’t even create artificial spaces where there is truly nothing. It is physically impossible to create what is called a “zero energy vacuum” or a void that doesn’t even have radiation. So where does “nothing” actually exist? We appear to have invented “nothing” out of thin air.

“Nothing” being physically impossible in our Universe, we are making a huge assumption and leap of logic that “nothing” (a concept humans invented and cannot replicate) existed “before” the Big Bang. In fact, the grammar of that statement is all wrong. We have no reason to expect that “nothing” as a concept truly exists somewhere outside the Universe and that it preceded the Big Bang when time didn’t even exist yet. By saying “something from nothing” we are making huge assumptions that we are not scientifically or logically entitled to make.

We have to unlearn some of our most basic concepts to understand the workings of a primeval Universe without the same rules it has now. The primate brain runs up against concepts we didn’t need to understand in order to survive and evolve. Our brains aren’t wired that way. It is like trying to send your friend a text using your toaster.

Seeking Answers at the Beginning

If you find yourself hit by a wave of existential disquiet and dissatisfaction about the mysteries of the Big Bang, consider the following.

1. We did not even confirm the Big Bang happened until sixty years ago. Imagine how many answers we will discover about the start of the Universe after another 100 or even 1,000 years of scientific endeavor.

2. If the answers to this puzzle are foreign to our primate brains and foreign to the fundamental physics of this Universe, then the answers (when we discover them) might sound like gibberish to us. They may not satiate the emotional and philosophical void and search for meaning we have assumed they would fill.

3. We may be looking for satisfaction in the wrong place by looking to the beginning of the story. Perhaps if we seek to add meaning to our lives, we must look at the present or perhaps even toward how we would like the story to end. In our own lives, we at least enjoy some measure of control over our own destiny. And if humanity continues to exist, our science and technologies continue to develop and our overall complexity continues to increase, who knows what profound superhuman impact we will have on the story in a thousand, a million or a billion years?

Philosophical satisfaction and existential meaning are frequently derived not from obsessing over our childhood traumas or what happened in the world before we entered it, but by making good and honorable use of the time given to us. If the earliest moments of the Universe prove anything, it is that seemingly tiny changes can be writ large into the fabric of the cosmos.

xs

chapter 2

Stars, Galaxies, and Complexity

Wherein the first hydrogen and helium atoms get sucked together into clouds • Those clouds become so tightly packed that the atoms fuse together • Fusion creates huge nuclear explosions that birth the first stars • Stars fuse hydrogen and helium into carbon, nitrogen, oxygen, and other elements, up to the twenty-sixth element of iron • The stars blow up in supernovas, creating heavier elements such as gold, silver, and uranium • All ninety-two naturally occurring elements are created by these terrifying H-bombs in the sky

As we have seen, 10–43 seconds after the Big Bang, the Universe rapidly expanded from the size of a quantum particle to the size of a grapefruit. For perspective, if the same rate of expansion had continued to happen, that grapefruit would have grown to the size of the current Universe in a fraction of a second rather than taking 13.8 billion years to do so. During that split second, tiny inequalities in energy appeared. Just a little bit more energy in dots sprinkled all over the cosmic grapefruit, differing from the almost equal distribution of energy found elsewhere in the Universe. It is those tiny dots with just a little bit more energy that spawned stars, galaxies, planets, and all the complexity that forms our history. Without these inequalities, complexity in the Universe would have been born “dead.” And this short history would be a great deal shorter.

As energy within those dots congealed into subatomic particles, the first matter emerged and the Universe continued to expand and cool.

Filled with a cloud of hydrogen and helium gas, the Universe continued to cool as it expanded to just a little above absolute zero, where it remains today. The vast majority of space from this point forward remained simple and cold, and there was no heat to forge further complexity beyond hydrogen and helium. Most of space was filled only with weak radiation. It was only in tiny pockets where inequalities in matter and energy reigned that things began to heat up.

The Fire-Soaked Origins of Stars

For millions of years, enormous clouds of hydrogen and helium floated through the ever-expanding cosmos. There was not much else among the gloom, and the Universe seemed pretty homogenous. Dull, dead, and without much change or history.

Over the course of 50 to 100 million years after the Big Bang (or, very roughly, the amount of time that separates you from Tyrannosaurus rex), gravity sucked hydrogen and helium gas together into increasingly dense clouds. Eventually the pressure at the core of these clouds became so intense that hydrogen atoms were smashed together and their nuclei fused. That is to say, the pressure overcame the usual nuclear repulsion that keeps atoms separate. Nuclear fusion (the same process that causes an H-bomb, or hydrogen bomb, to explode) let off a huge burst of energy and suddenly these clouds were transformed into gigantic fireballs generating heat and throwing it out into the Universe as energy. The first stars were born. This fusion lasted as long as the stars had more gas to guzzle.

Fusion in the heart of a star achieves a minimum of 10 million Kelvin (about 25,000 times the temperature of a hot summer’s day). For the first time since the first three minutes after the Big Bang, some new elements were created.

Billions of stars were born across the Universe. The first generation of stars that emerged 50 to 100 million years ago were huge because of the fresh supply of gas in their neighborhoods—about 100 to 1,000 times as massive as our Sun. Because of their size, they did not live for more than a few million years. But when they blew up, their materials were sucked back together into second-generation stars, which were smaller but could live for longer—into the billions of years.

The Milky Way

Gravity began to attract stars to each other, and they formed clusters that were 30 to 300 light-years across. These clusters merged into even bigger ones. From 13.7 to 10 billion years ago, these mergers continued in our region of space to create the Milky Way, which is roughly 100,000 light-years across. Our galaxy contains about 200 billion stars. And the same process of galactic mergers occurred all over the Universe, forming the estimated 400 billion galaxies that exist in the Observable Universe.

The Creation of Galaxies

From 13 billion to 10 billion years ago, different kinds of galaxies came into being. Spiral galaxies (like our own Milky Way) form 60 percent of the estimated 400 billion galaxies in the Observable Universe. They do the majority of star formation. But their bulbous cores contain such a concentration of stars that they are hostile to the formation of life, with supernovas ripping through the sector far too frequently. It is only at the arms of spiral galaxies, where our solar system has drifted, that star systems are distant enough from each other to form life.

Lenticular galaxies (such as the Sombrero Galaxy) have the same bulge but no arms. They make up roughly 15 percent of galaxies in the Universe. They have very little star formation.

Elliptical galaxies (such as Hercules A) have no bulge at the center and stars are more evenly distributed. They are “dying” galaxies and very little new star formation happens within them. They constitute 5 percent of all galaxies in the Universe.

Irregular galaxies are the hodgepodge of malformed galaxies that are not easily categorized. They make up 20 percent of all galaxies. Most of them are quite small and are usually misshapen by the gravitational pull of another galaxy while they are forming. Some currently have no explanation.

As for the number of galaxies in the Observable Universe, 400 billion is the established estimate. However, recent studies suggest that the number could be between 1 and 10 trillion. This—considerably higher—number increases the odds that complex life might be evolving somewhere else out there. Each galaxy can contain millions, billions, or even trillions of stars. That is quite a few rolls of the evolutionary dice.

The Life Span of Stars

The size of a star determines how long it lives, because of how quickly it burns its fuel. Stars that are over eight times the size of the Sun go supernova. Stars that are smaller than that die without exploding and creating heavier elements. The largest stars burn for only a few million years, slightly smaller stars might burn for a few hundred million years, even smaller stars might burn for a few billion years, and the smallest, slowest-burning stars can burn for a potential 100 billion to several trillion years.

The first generation of stars to form after the Big Bang were huge and blew up billions of years ago. The second generation of stars, created from the exploded remnants, contained heavier elements that were created in the bellies of the first generation of stars. Most of the second-generation stars have also died in the past 13 billion years, but many of them are still detectable in the Universe and within the Milky Way galaxy.

The third generation of stars is only a few billion years old. They possess a vast diversity of heavy elements created in the previous two generations. The third generation is also likely to have more planets orbiting them because of the abundance of elements that would have formed a ring of dust around them and eventually turned into planets. Thus, third-generation stars (like our Sun) are the best bet for further complexity.

Cosmic Flora and Fauna

Our Sun is a Yellow Dwarf, a kind of star that lasts 4 to 15 billion years and represents 10 percent of the stars in the Universe. Slightly smaller stars, called Orange Dwarfs, live 15 to 30 billion years and make up another 10 percent. Red Dwarfs are the smallest stars (about 5 to 50 percent the mass of the Sun) and make up 70 percent of all the stars in the Universe. Red Dwarfs can last hundreds of billions of years—or even trillions, depending on how small and slow-burning they are. None of these stars explode in a supernova when they die, but slowly burn down and flicker out.

When a star like our Sun burns up all its hydrogen and helium fuel, it starts burning through progressively heavier elements in its core. As a result of this process, Yellow Dwarfs bloat like a dead cow in a wet field and become Red Giants. After another billion years or so, they shrink back and become White Dwarfs—the skull and bones of stars like ours which have stopped fusing atoms in their cores. These dwarfs last for another few million years before finally flickering out completely. Red Giants and White Dwarfs make up approximately 5 percent of stars in the Universe.

The remaining 5 percent of stars are decidedly rarer but much more essential to complexity. These are the stars that blow up in supernovas. Supergiant stars only burn for between a few million years and a few hundred million years (depending on their size). These Supergiants are capable of fusing all the atoms in the periodic table up to iron—the twenty-sixth element. Thereafter, no star’s core burns hot enough to fuse anything more. Once the Supergiants run out of fuel, their massive structures collapse in on themselves, letting off a huge explosion—a supernova. The supernova itself burns so hot that during the process even heavier elements are forged, such as gold, silver, and uranium. Supernovas are responsible for producing the ninety-two naturally occurring elements in the Universe. The fact that some elements (such as gold) only exist because of the supernovas of less than 5 percent of stars is why these elements are so rare.

When stars blow up in supernovas, they leave behind neutron stars as their dead remnants. Neutron stars are extremely dense and heavy and don’t burn very brightly. If two neutron stars smash into each other, they can create even more of the heavy elements. They are also tiny, being only a dozen or so miles across. All that mass in such a small space makes them very vulnerable to turning into black holes.

A black hole is essentially a pile of matter with such a high mass that the gravity sucks it in on itself. Their gravity begins to suck in matter around them, distorting the space in their neighborhoods. While black holes may just be sloppy piles of matter, there are some hypotheses that black holes warp space and time around them to such an extent they may have bizarre properties. For instance, they may break down the laws of physics, make the passage of time incoherent, or perhaps even link to other dimensions or other universes.

Stars with Chemistry

The periodic table currently holds 118 elements. While ninety-two elements are found naturally around the Universe, any of the higher elements that form in nature would almost immediately degenerate into lower forms. Higher elements have been created in human laboratories, the most recent one being #118, Oganesson, created by a Russian–American team in 2002.

Complexity rose within stars as they went through their life cycles. Then they died and flung those elements out into the Universe again. They would form the building blocks for further complexity. An almost innumerable number of combinations of chemicals. To date, there are an estimated 60 to 100 million chemicals out there.

A chemical is built upon a combination of elements strung into a higher structure: a molecule. This can create a structure such as H₂O (two hydrogen atoms and one oxygen atom) to make water, or a structure such as SiO₂ (one silicon and two oxygen) to make quartz, the most common mineral on Earth, or it can create a manmade structure such as C₂H₄ (two carbon, four hydrogen) to make polyethylene, the world’s most common plastic.

Then there are more complex chemicals, such as organic proteins, which are immense tangles of thousands of atoms, like the protein dubbed “Titin,” the chemical formula of which is C169,723H270,464N45,688O52,243S₉₁₂ and which gives your muscles their elasticity. The technical name of this chemical is roughly 190,000 letters long and takes somewhere between three and four hours to fully read out loud. Such is the immense scope for complexity once elements start forming into molecules! Same goes for the chemical formulas for the bases of DNA (adenine, guanine, cytosine, and thymine), which encode genetic traits and allow organic material to self-replicate, evolve, and become alive.

Once the ninety-two naturally occurring elements in the cosmos emerged and started combining into different chemicals, the Universe had all the ingredients it needed to create the complexity we see around us today.

But what is complexity?

The Unifying Pattern of All History

The unifying pattern of all history over 13.8 billion years is increasing complexity. It is the process that created us and is, in turn, the process through which we create. After the Big Bang, the first particles of matter appeared and slowly transformed into stars. These stars would create all the chemicals that compose the Earth (including life). The same increase of complexity defines human history—from foraging, to ancient agriculture, to modernity. It is very rare in the chaos of history to find a thread that stretches across all events from beginning to end. Increasing complexity is the only such trend that has yet been identified.

A complex thing is composed of matter, intricately woven like a tapestry. It is sustained in its shape by flows of energy that “feed” it. For instance, stars require more gas to burn. Humans require food. Mobile phones require batteries. It is all the same principle—we need flows of energy to keep from dying. That is a general rule of all complexity throughout the Universe.

Matter and energy were born within the white-hot speck of the Big Bang 13.8 billion years ago. All the ingredients for all the stuff we see around us was there at the beginning. The history of the entire Universe boils down to a history of their perpetual transformation into new and brilliant forms.

No new matter and energy were added to the Universe after the Big Bang. This is the First Law of Thermodynamics acting in full force: Nothing new is created, nor is anything old totally destroyed. That means the atoms that make up your body existed in some form at the beginning of the Universe and have continued to exist and evolve across the cosmos over 13.8 billion years. You are, after a fashion, 13.8 billion years old.

And after you die, those atoms will split off in different directions and continue to evolve in the Universe again. From a certain point of view, we are the Universe, one totality, and we are blessed—briefly—to be a self-aware part of it. As if the Universe were looking at itself in a mirror.

The Mechanics of Complexity

Complexity is an ordered structure that is created and sustained by the flow of energy. A hydrogen atom is a structure composed of one proton and one electron. A water molecule is a structure of two hydrogen and one oxygen atoms. A human brain is a form of complexity, as is the toaster that a human brain invented. The human web of 8 billion people, involving trade and information exchange, is one of the most complex systems of all.

The greater the diversity of building blocks in a form of complexity and the more intricately it is constructed, the more complex it is. A star has a lot of hydrogen atoms in it, but it is not particularly complex; it is just a big disordered lump of them. Contrast that to a dog, which has a much more complex tangle of chemicals, DNA, liver cells, brain cells, blood vessels, and highly complex respiratory, circulatory, and nervous systems. Move a few thousand atoms of hydrogen from the core of the Sun to its surface and it keeps running as if nothing happened. Replace a dog’s brain cells with its liver cells and the dog is not going to be chasing birds anymore.

In order for any form of complexity to be created, some energy needs to be used. Like welding a car engine together in a factory. In order for that complexity to be sustained, you need more energy flow. Like eating food in order to stop from starving and dying. And in order for something to increase in complexity, it needs more energy flows altogether. If those energy flows cease, the structure decays and the thing gradually dies. A car sputters out and stops, a plant withers away and dies, a civilization collapses into abandoned ruins. This is also why complexity can be measured in the density of energy that is flowing through it.

complex systems

energy flows (erg/g/s)

The Sun

2

A Supergiant star near to supernova

120

Algae (photosynthesising)

900

Cold-blooded reptiles

3,000

Fish and amphibians

4,000

Multicelled plants (e.g., trees)

5,000–10,000

Warm-blooded mammals (average)

20,000

Australopithecines (early primates)

22,000

Human foragers (Africa)

40,000

Agricultural society (average consumption)

100,000

Nineteenth-century textile machine

100,000

Nineteenth-century society (average)

500,000

A Model-T automobile (c. 1910)

1,000,000

A vacuum cleaner (present)

1,800,000

Modern society (average consumption)

2,000,000

Average airplane

10,000,000

A jet engine (F-117 Nighthawk)

50,000,000

The more structurally intricate a form of complexity is, the greater the amount of free energy density it requires. The simplest and oldest complexity in the Universe, like a star, doesn’t require that much energy per gram, whereas the products of billions of years of biological evolution or culture burn through a higher density of energy flows.

The Birth of Complexity

A split second after the Big Bang, there were slight ripples in space-time (quantum fluctuations) that created clumps of energy unequally distributed across the cosmos. You can see these clumps recorded in the “snapshot” of cosmic background radiation 380,000 years after the Big Bang. As a result of these clumps, energy congealed into the first particles of matter. If it weren’t for this unequal distribution of energy, complexity would not exist.

In order for complexity to exist, you need energy flows to create and sustain it. In order to have energy flow, you need to have flow from where there is more energy to where there is less.

If all energy were equally distributed at the start of the Universe, there would be no need for energy to move. Nothing would have changed. Nothing would have happened. There would have been no complexity, just a blank cosmos of thinly distributed radiation from start to finish. In a nutshell, there would have been no history.

Instead, the first clumps of unequally distributed matter and energy created the first stars. These stars created all the other naturally occurring elements in the periodic table. These elements came together to form molecules and planets. On one such planet, Earth, more of these molecules came together to create life. And some of that life evolved consciousness and the ability to invent stuff and continually tinker with and improve upon those inventions.

All the while, from stars, to life, to technology, we required more energy flows to create, sustain and increase complexity. And so tiny pockets of the cosmos have been getting more complex over the past 13.8 billion years. That is the unifying theme of all history. The Big Bang created unequal amounts of energy across the cosmos, then for 13.8 billion years energy has been evening itself out again, and as a result of that we had energy flow and all the wondrous things that emerge from that.

The Death of Complexity

However, there is some irony to the increase of complexity in history. The reason why energy flows from stars to feed plants, which nourish animals, to give energy to brains in the human web is because of the Second Law of Thermodynamics. That law compels energy to want to even itself out—and it can only do that by flowing from where there is more energy to where there is less. In the short term, this energy flow can create complexity. But ultimately because the energy flow evens itself out, there is no more energy flow left, which kills complexity.

It is the principle that creates life and in exchange eventually takes life. Only death pays for life. This sounds like philosophy, but it is also a universal reality.

Only in tiny pockets of the Universe where there has been an unequal distribution of energy does complexity continue to rise. In the rest of the Universe, about 99.9999999999999 percent of space is already dead, unable to generate more complexity. This is why the clumping of energy in the first split second of the Universe was so crucial to our existence.

The more complex something is, the more energy flow it requires and the faster it uses up energy flows. For example, a dog requires more energy flow per day than a tiny colony of bacteria. And a car requires so much energy that it needs to use the stockpiled energy of millions of years of organic material crushed underground and transformed into oil and petrol. Dogs poo, cars spew smoke out of their exhaust pipes, and some of that waste cannot be used again. Ever.

Eventually the Universe will run out of energy completely. After trillions upon trillions of years. So in reality, complexity is just a by-product of a longer tale in history, in which the Universe is trying to revert back to a realm of equally distributed energy. The endgame is a Universe that is nothing more than a weak orb of radiation. A quiet cosmos with no history, no change, and no complexity. This is a state referred to as heat death.

The collapse of complexity is a threat throughout our story, and we will come back to the menace of heat death as we approach the end of our tale. For now, just remember that the source of our existence is also the source of our potential nonexistence. The Second Law of Thermodynamics is at once the creator and the destroyer of worlds.

The only way the Second Law could be defied is by a supercivilization many millions of years of scientific progress from now becoming so complex that it can manipulate the fundamental laws of the Universe itself.

chapter 3

Origin of the Earth

Wherein the Sun forms and greedily sucks in 99 percent of all matter in the solar system • The remaining 1 percent forms a ring of dust around the Sun over a light-year wide • In each orbit, the dust accretes into planets, dwarf planets, asteroids, and comets • In one such orbit, the Earth forms from a series of terrifying collisions • The Earth cools and differentiation and bombardments create the first oceans • Within those oceans, long strands of organic chemicals begin to form

Our galaxy, the Milky Way, began from a cluster of the first giant stars about 13.5 billion years ago. Early on, it began to spin and assumed the shape of a flat disc with a bulge at the center. As nearby galaxies were drawn into its gravitational pull, the Milky Way merged with them and grew in size. By 10 billion years ago, the last of the galactic mergers had happened. Today, our galaxy is 100,000 light-years across and contains 200 to 400 billion stars.

The first generation of stars had completely died only a few million years after the Milky Way had formed. The hydrogen, helium, and heavy elements created in their massive supernovas were sucked together again by gravity to form entirely new stars. The second generation of stars continued to twinkle for billions of years.

Then 4.567 billion years ago, one such star, located 1 light-year from where our solar system is now on a spiral arm of the Milky Way, exploded in another supernova. This explosion seeded the region with the ninety-two naturally occurring elements, from hydrogen to uranium. The burst of energy from the supernova triggered a nearby cloud of hot gas to begin the process of forming a third-generation star. Our Sun’s fires flared into life for the first time. Due to the Sun’s massive gravitational pull, the overwhelming majority of matter in the solar system was sucked into the Sun. The remaining 1 percent of stuff formed a disc of tiny dust particles around the Sun, the leftovers of the process stretching on for a light-year in every direction.

The dust of the early solar system contained all ninety-two elements, which swiftly began to form into sixty different chemicals in the vacuum of space. The Sun’s first fusion ignitions blasted the majority of the hydrogen and helium gas into the outer solar system, which is why the inner planets (Mercury, Venus, Earth, Mars) are rocky and the outer planets (Jupiter, Saturn, Uranus, Neptune) are gas giants.

The Solar System

The dust around the Sun formed a flat disk and began to spin around it, much in the same way the arms of the Milky Way spin around its bulbous center. This is the origin of our orbit around the Sun. As the dust began to spin, they formed orbital “tracks” where everything in each orbit began to gently stick together from static electricity. In every orbital track where there is now a planet, the dust would rapidly become the size of rocks, and then the size of boulders, and then the size of mountains.

Within 15,000 years, the solar system was full of millions of objects that were over 6.2 miles (10 km) across. Then the collisions became decidedly less gentle. The smashing together of these objects generated heat, which pasted the two colliding objects together. After about 10 million years, the solar system had about thirty or so protoplanets, each roughly the size of the Moon or Mars. The exception was the Asteroid Belt, where the gravitational pull of nearby Jupiter prevented numerous asteroids from colliding with each other and accreting, rendering the Belt a “failed planet.” A few million years later, these protoplanets also collided in terrifying crashes, forming just eight planets in each orbital track.

1. Mercury is 3 light minutes from the Sun and 5 percent the size of Earth. It suffers from extreme temperatures: –274°F (–170°C) at night to 800°F (427°C) during the day.

2. Venus is 6 light-minutes from the Sun, and the planet is a very similar size to Earth. It could have spawned life were it not for the horrific thick atmosphere of carbon dioxide, which traps a lot of heat from the Sun and sees surface temperatures hot enough to melt lead.

3. Earth is 8 light-minutes from the Sun. In terms of distance, it is within the habitable zone from the Sun. Naturally, we know that conditions on Earth were right for life. We shall return to Earth shortly.

4. Mars is 12.5 light-minutes from the Sun and is 10 percent the size of Earth, which means it cannot capture much of an atmosphere—roughly 1 percent as thick as Earth’s. This means that Mars cannot maintain water in liquid form. Most water on Mars is locked away as ice, which makes life less likely.

5. Beyond the Asteroid Belt, Jupiter is 43 light-minutes from the Sun, made of 99 percent hydrogen and helium. It is eleven times the diameter of Earth and roughly 320 times Earth’s mass. Jupiter has violent weather patterns that would obliterate anything resembling life. Underneath all that thick cloud, the surface may be composed of a lot of solid hydrogen; that is, hydrogen gas that is so compressed it takes on a solid appearance. The moons of Jupiter may have fostered life, as—theoretically—the moon Europa may have, but whether or not they have remains a mystery.

6. Saturn is 78 light-minutes from the Sun, nine times the size of Earth, and has ninety-five times its mass. Like Jupiter, it also would not make a very good prospect for life. However, Saturn has managed to capture sixty-two moons and a ring of ice and rock, which is its signature (Jupiter also has a ring but it is much smaller). The most likely candidate for life is Titan, but life would have to have evolved very differently there than life on Earth. The temperatures are so cold that water is always frozen solid and methane gas takes the form of liquid. So if life evolved in methane oceans, it would have to have a completely different form of respiration than the life that evolved in Earth’s oceans.

7. Uranus is 2.5 light-hours from the Sun, four times the size of Earth and is the coldest planet in the solar system. Wind speeds are horrific, and in many ways the atmosphere and immense pressure resemble the other gas giants, making higher complexity extremely unlikely to have arisen there.

8. Neptune is 4 light-hours from the Sun, the furthest planet in the solar system. It is so distant that it takes 165 Earth years to make one orbit of the Sun. Much like Uranus, Neptune is extremely cold, with a hydrogen and helium atmosphere and a core made up mostly of ice and rock.

9. Pluto used to be considered a planet since its discovery in 1930 as the farthest planet-like object we could see with telescopes at the time, approximately 5.5 light-hours from the Sun. But Pluto has not cleared all the other objects from its orbit, like the eight planets have. And decades later, other dwarf planets were discovered out there, some of them bigger than Pluto, such as the dwarf planet Eris. So, sadly, Pluto was stripped of its planetary status in 2005. The fact that it shares its name with a cartoon dog has not aided this transition in status.

10. The Kuiper Belt begins 5 light-hours from the Sun and stretches in a ring of planetary shrapnel as far as 7 light-hours. It contains dwarf planets such as Pluto, Eris, Charon, Albion, Haumea, and Makemake. The Kuiper Belt also contains a number of asteroids, and simple frozen balls of water, ammonia, and methane. The total mass of the Kuiper Belt is unlikely to weigh much more than 10 percent the mass of Earth. Hence, there was not enough material for a large planet to emerge there.

The Oort Cloud begins approximately 27 light-hours from the Sun, meaning light takes over a day to travel there, but it is still held by the Sun’s gravity. It is composed of icy planetesimals and comets. It stretches onward for an entire light-year from the Sun. It might even extend as far as 3 light-years from the Sun, nearly to our neighboring star, Proxima Centauri, which is 4.2 light-years away. This sphere of ice represents the very edges of our solar system, and the border between us and the rest of the galaxy.

Beyond our solar system, the Milky Way contains 200 to 400 billion stars. Many of these star systems also contain planets. We’ve found thousands of exoplanets (planets external to our solar system) in nearby solar systems by looking only at roughly 0.0000000000000000009 percent of the total number of stars in the galaxy. In total, there must be trillions of planets in our galaxy. It is estimated that 300 million planets in the Milky Way may be capable of sustaining life just like Earth can. These are tremendously good odds that life has emerged elsewhere and that we are not alone in the Universe. Especially when one considers there are 400 billion to several trillion galaxies out there.

The Earth

As the thirty protoplanets of the early solar system continued to crash together in apocalyptic collisions, the resulting planets got bigger and bigger. Around 4.5 billion years ago, there were two planets in the orbital track where the Earth now is. I think you know where this is going . . .

One planet about the size of the Earth and another planet about the size of Mars, which we call Theia, smashed together. The Earth-size planet absorbed most of the rubble and reformed. But 1.2 percent of the matter drifted into Earth’s orbit as wreckage from the collision. These shards cobbled together to become the Moon.

The Earth at this time remained extremely hot, as the fires of planetary collisions continued to burn. The Earth was also being pelted constantly by asteroids, each impact as devastating as a nuclear war. As the Earth continued to hoover up the surrounding matter in its orbit, the pressure from the weight of all that “stuff” created heat in the Earth’s core. In short, Earth 4.5 billion years ago was melted and squishy. A gelatinous ball of pudding that burned and bubbled at thousands of degrees.

This kicked off the process of differentiation. The Earth was a molten ball of squishy semi-liquid rocks, through which material could pass reasonably freely. Many of the heaviest elements like iron and gold sank through the scorching soup down to the very core of the Earth. The iron created a ball 2,100 miles (3,400 km) thick at the core of the Earth, giving the planet its magnetic field.

Only tiny traces of these heavier elements remained trapped in the cooling Earth’s crust. Which is why something like gold is so rare for humans to find. Yet if you were to somehow be able to burrow into the molten recesses of the mantle and core of the Earth, you would find enough gold to coat the entire Earth’s surface, gilding the continents from sea to sea.

Lighter elements bubbled to the surface. To the top of this soup bubbled forth a crust of silicon (the majority share of Earth’s chemical composition) and also aluminum, sodium, and magnesium. The lightest of all elements, like carbon, oxygen, and hydrogen, were ejected as gases to form the Earth’s early atmosphere.

Earth and Theia colliding

Yet the cooling of the crust was frequently interrupted by asteroid impacts in the Late Heavy Bombardment. No sooner did the crust begin to congeal at the top of molten soup than more impacts destroyed the thin layer and heated the world up again. It was only around 4 billion years ago that the bombardments were over and the crust was able to fully solidify.

Even in this lava-soaked hell, higher complexity formed on our planet. Roughly 250 chemical combinations were possible as Theia crashed into the Earth. And over 1,500 different chemicals existed by the time differentiation had finished its work.

Taking Mother Earth’s Measurements

Even today, the crust is thin and frail by the standards of the rest of Earth’s structure. This may be surprising when you consider how thick the rocky edifices of mountains and the dark, stony halls of mineshafts appear to be to human perception. But it is quite apt to call it the “skin that forms at the top of a pot of soup.” The crust, which contains a lot of the Earth’s lighter elements and just smidges of the heavier ones, is only about 21.7 miles (35 km) thick and in some places at the bottom of the oceans about 4.3 miles (7 km) thick.

Below the crust is the upper mantle, where there is so much pressure that temperatures increase to over 1,832°F (1,000°C), producing the horrific lava that occasionally spews to the surface from volcanoes. The upper mantle runs about 403 miles (650 km) deep, in a sea of molten igneous rock. Below that is the lower mantle, which runs down to 1,801 miles (2,900 km) deep, where it is so hot that rocks take a fully liquid form.

Further down is the core. The outer core is composed primarily of liquid iron and nickel, which flows down to 3,231 miles (5,200 km) below the surface, and then the inner core, which runs down 3,978 miles (6,370 km) to the very middle of this hell, and experiences so much pressure that the extremely hot molten core nevertheless behaves as if it were solid. At the core of the Earth, temperatures increase to 12,000°F (6,700°C).

The Earth’s crust, mantle, and core

Hell on Earth

The Earth from 4.5 to 4 billion years ago belongs to the Hadean eon, so called because of the hellish conditions on Earth at the time. The surface of the Earth remained above 212°F (100°C), preventing any liquid water from forming, and in some places temperatures were as high as 2,732°F (1,500°C) and Earth was covered in oceans of lava.

Where there was land, it was paper-thin and jets of steam were shooting up out of its cracks as the lighter gases escaped the Earth in the process of differentiation. This job was also done by volcanoes, which rose out of the Earth, spewing lava, smoke, and ash. As that lava dried into crust and built up, some volcanoes grew higher than Mount Everest.

The sky itself was a terrifying red. This was caused by the predominantly carbon dioxide atmosphere (about 80 percent). It would be a long time before Earth adopted an oxygen atmosphere; for now, oxygen remained at negligible levels. And because the Sun was still young and not burning as brightly yet, this had the other haunting effect of making the sky fairly dark, aside from the redness. If there had been an “eye of Sauron” hovering in the sky, like in The Lord of the Rings, it would not have looked entirely out of place.

When Theia smashed into the Earth approximately 4.51 billion years ago, a lot of the crust was destroyed and flung up into space along with an immense amount of lava. One cannot understate the catastrophic nature of a Mars-size planet smashing into Earth; if it were to happen today, it would wipe out every trace of life and perhaps even evaporate all the oceans. It would have been roughly 450 times more severe than the asteroid impact that wiped out the dinosaurs 66 million years ago.

As the Moon slowly accreted and appeared in the sky, it was much closer to Earth than it is today (it moves away at about 1.5 inches/4 cm a year) and would have blocked out much of the sky as it passed overhead. The tidal force exerted by the Moon would have been correspondingly greater. Leveraging massive tsunamis thousands of feet high to wash across the Earth every twelve to fifteen hours. Except these tsunamis were not made of water—they were made of molten lava.

But it gets worse. For 500 million years, the Earth was pelted by asteroids in the Great Bombardment, and particularly severely around 4.1 billion years ago in the Late Heavy Bombardment. This is where millions of asteroids struck the Earth, shattering its already thin and fragile crust. As Earth swept up the remaining cosmic debris in its region of the solar system, it suffered continual catastrophic impacts. Some of these would have been as powerful as a nuclear holocaust, some as bad as the Cretaceous impact that killed the dinosaurs, and some of them would have been up to 100 times worse (literally), depending on the size of the asteroid. And unlike the Cretaceous extinction, which happened once 66 million years ago, these impacts were happening constantly.

It goes without saying that any form of life would perish under these brutal conditions. There was no room for something as intricate as life in any place in the solar system at this point. Something on Earth needed to change for life, microscopic and frail, to stand a snowball’s chance in hell of forming.

The First Oceans

Despite the destruction, it appeared that roughly 500 million years of hell was quite enough. All that differentiation had belched hydrogen and oxygen into the atmosphere in a process called “outgassing.” The bombardment of millions of asteroids had brought tons of ice from outer space. This promptly melted and rose into the atmosphere as well. Over time, the crust had cooled into a black and gray igneous landscape, with no more oceans of lava. And the surface temperature fell below 212°F (100°C) and continued falling. Suddenly all that water vapor that had built up in the atmosphere had no choice but to fall to Earth.

What followed was something that would resemble the biblical flood. But never mind raining for forty days and forty nights; the torrential downpour across the planet continued for millions of years without end. The trenches and low-lying areas of the Earth’s crust began to fill up with water. By approximately 4 billion years ago, the Earth was covered with oceans. Only the highest ledges, our continents, managed to keep their heads above water. And even these became pockmarked with lakes and streaked with rivers. Four billion years ago, the Hadean eon was over; the Archean eon had begun.

There are a few things to note about the Archean world. First, the Earth below the crust was still much hotter, since it had only recently formed, and emitted a lot of geothermal energy, which would be useful for the first forms of life. This compensated for the fact that the Sun’s energy (solar thermal energy) was still quite dim, so was a less appealing power source for early life. But even if life had emerged on the surface, the solar radiation blasting down on the surface of an Earth without an ozone layer would have destroyed any life that tried to form. So, for now, the best bet for life was deep in the oceans, where it was warm and safe from radiation.

Archean Earth also had a gigantic Moon, which passed overhead, pulling tremendous tides from shore to shore. At least those waves were no longer lava. But the land itself was still dotted with an abundance of volcanoes as eruptions and outgassing continued. These volcanoes pumped out primarily carbon dioxide, which was still the dominant gas in the atmosphere. The other important thing to note about the land is that it was entirely rocky. All the greenery we associate with plains and forests did not exist yet. Instead, the Earth looked more like the surface of the Moon. Just add water.

And so the Inanimate Phase came to an end. The Archean Earth sat soulless and silent except for the sound of waves beating the rocky shore. It could have remained that way forever. If not for a highly unlikely event, our history would have already drawn to a close. For the next phase of complexity, we need to look to the bottom of the oceans. It is here we will find the first microscopic seeds of our family tree.

part two

The Animate Phase
3.8 billion–315,000 years ago

chapter 4

Life and Evolution

Wherein the Earth becomes slightly less deadly, giving life a fighting chance • Differentiation and asteroid impacts create the world’s first oceans • Within those oceans, long strands of organic chemicals begin to form • Those organic chemicals begin to self-replicate and evolve, triggering the existence of life • Some of that life becomes photosynthesizers • These photosynthesizers mess up the atmosphere and kill off a bunch of life • Against adversity, eukaryotes and sexual reproduction evolve • The final Snowball Earth event creates the first multicelled life

In the tranquil smoldering seas of the Archean Earth, 3.8 billion years ago, life began. We derive that date from chemical signatures left in Archean rocks by early microscopic life. By 3.5 billion years ago, we can actually see the fossil “footprints” of these tiny microbes. Even this simple primitive life outstripped in complexity everything we have seen thus far.

By 4 billion years ago, the Earth’s surface temperature had dropped below boiling point, and millions of years of rainfall created the first oceans. These were essential to life because it could not form if entombed in solid rock, where it could not move around. Or being fried by radiation on the Earth’s surface. Or in the wispy gases of clouds. Liquid water was the ideal environment that allowed organic chemicals to move and join together in a soup-like mixture. Primitive life was fragile; it was a miracle it formed at all. The safest bet was to dwell at the bottom of the oceans.

But where would life get its energy flows, from which higher complexity could be created? The most likely answer is from undersea volcanoes or “vents,” which pumped out geothermal energy from cracks in the Earth’s crust. Microbial life sat on the edges of these volcanoes, basking in the heat.

So we have the soup, we have the stove: Now we just need the ingredients. The Archean oceans were teeming with a variety of organic chemicals that had bubbled to the surface via differentiation. It is no surprise that most of those organic chemicals, such as carbon (on which all terrestrial life is based), are among the lightest in the periodic table. Carbon is also the most flexible. It forms a vital link in the chain for about 90 percent of all the chemical combinations that we have discovered.

Besides carbon, equally vital to self-replicating life are hydrogen, oxygen, nitrogen, and phosphorous. On the edges of undersea vents 3.8 billion years ago, the elements above came together to form complex organic chemicals: amino acids and nucleobases, long strings of building blocks.

Amino acids are crucial for fueling life. You can find them in your food. They are a combination of carbon, hydrogen, oxygen, and nitrogen atoms, wrapped in a chain of about nine atoms. Amino acids are the building blocks of proteins. Each protein is a tangled strand of about twenty amino acids on average, though some have considerably more. A protein is used to carry out the various commands of a living cell: to burn energy to sustain its complexity, to reproduce, to grow various traits, to react to its environment, and also to simply move things around a cell.

Nucleobases, on the other hand, are the building blocks of nucleic acid (the fundamental component of DNA and RNA). These key chemicals are adenine (C₁₀H₁₂O₅N₅P), guanine (C₁₀H₁₂O₆N₅P), cytosine (C₆H₁₂O₆N₃P), and thymine (C₁₀H₁₃O₇N₂P). As you can see, we’ve come a long way in complexity since the first hydrogen atoms (H) at the start of the Universe.

Deoxyribonucleic Acid: The Sexiest Acid of Them All

DNA exists in all living cells and is the database that tells proteins what sort of traits those cells should have and how they should behave. It is the “software” of the organic computer, the disk that contains the program instructions that runs a video game. DNA is what makes living things look and act like they do. From fangs to freckles, from growling to laughing.

Deoxyribonucleic acid is made of two strands composed of billions of atoms, twisted around each other in a double helix. Each strand is composed of many nucleotides, which in turn are composed of the nucleobases mentioned earlier, which may well have formed in the oceans of Archean Earth. Adenine, guanine, cytosine, and thymine are the nucleobases that hold the genetic information. They are like the 1s and 0s encoded on a computer game disk.

Which brings us to the “hardware” of our organic computer: ribonucleic acid, or RNA. Made of only one strand rather than two, RNA has the task of taking the instructions from DNA and delivering them to small parts in a living cell that produce proteins (these protein factories are called ribosomes). RNA does this by unzipping DNA and reading the instructions, or the 1s and 0s. The RNA then gives the proteins their marching orders. And those proteins set about building the organism. RNA and the proteins are essentially the disk reader and the hard microchip components of the computer itself.

About 3.8 billion years ago this highly structured, organic, acidic sludge started carrying out some highly intricate but seemingly arbitrary chemical reactions. But how did it evolve?

The Source of Evolution

How we went from basic organic chemicals to a structure as complex as DNA and RNA remains a blank page in our history. But once those structures were in place, their chemical reactions didn’t happen just once.

DNA self-replicates, or copies itself, in order to continue giving instructions to the rest of a living cell. When it does so, it splits in two. Most of the time this copying process is perfect. But occasionally there is a copying error, or mutation, which slightly modifies DNA’s instructions. A mutation happens maybe once in every billion copies. When the DNA mutates, it creates a slightly different organism.

If DNA copied itself flawlessly every single time without a single failure, life would have remained exactly as it was 3.8 billion years ago on the edges of undersea volcanoes. It would not have evolved. Mutations create historical change in biology.

Some mutations are deadly to the organism, some don’t affect its survival one way or another, and some mutations are useful. Those mutations that are useful are able to copy themselves all over again, and the cycle continues. Those mutations that work the best in a specific environment continue to exist. If not, those mutations (and the organisms possessing them) die out.

That is what evolution actually is: the natural selection of genes based on their evolutionary usefulness, rather than selection of the individual or the entire species. As environments change, so do the genes that work the best.

Thus, in this collection of organic sludge, we have all the key traits of a living organism: It uses energy flows from geothermal vents and surrounding amino acids (metabolism: that is, it eats), it reproduces by copying itself (reproduction), and it gradually changes its traits based on useful mutations (adaptation). These three traits of metabolism, reproduction, and adaptation are the best idea we have when it comes to defining what the heck life is, and how it differs from the inanimate cosmos.

Once the process of self-replication and evolution began 3.8 billion years ago on the edge of underwater volcanoes, that organic sludge transformed into a diversity of strange new forms, eventually covering the whole Earth. Every bacterium, every plant, every animal and every human today is shaped from that 3.8-billion-year-old lump of clay. As Darwin wrote at the end of On the Origin of Species, “From so simple a beginning, endless forms most beautiful and most wonderful have been, and are being, evolved.”

The First Photosynthesizers

The first organisms to emerge at the bottom of the oceans took in geothermal energy from undersea volcanoes and chomped down the chemicals around them. These organisms were, of course, quite simple. These were the “prokaryotes”: microscopic, single-celled organisms without a nucleus. Their DNA floated openly around the cell, increasing the risk of it getting damaged. These prokaryotes did not have sex (quelle horreur!) but cloned themselves, by splitting into copies. Each cell split and copied itself every few minutes; some could clone themselves in mere seconds.

The Archean oceans filled with these tiny organisms. There was a shortage of chemicals at the bottom of the ocean, not to mention a shortage of “real estate” around the edges of underwater volcanoes. There was an evolutionary incentive for some prokaryotes to move toward the surface of the oceans. But to do so they abandoned geothermal energy and evolved to use the Sun’s energy instead.

Prokaryotic cell

By 3.4 billion years ago, the prokaryotes near the surface of the oceans were using water, sunlight, and carbon dioxide to feed themselves. Just like plants today. These prokaryotes were the first photosynthesizers. They would eat the hydrogen from the water and the carbon from the air, fueling the process with solar energy. The leftover oxygen from the carbon dioxide was discarded as a waste product.

All these slight microbial changes took 400 million years. That’s over 5 million average human life spans. The same space of time that separates us from the first “fish” that crawled out of the oceans and onto land . . .

Some photosynthesizers began to form large colonies: big mounds of microbes 1.5 to 3 feet (50–100 cm) in height, called stromatolites. Fossilized remains of these colonies can be found at Shark Bay in Western Australia today. They are roughly 3 billion years old.

The Oxygen Holocaust

Even at this early stage, living things had the propensity to screw up the environment. I mentioned that the first photosynthesizers excreted oxygen as a waste product (O₂ left over from eating carbon dioxide). This was basically harmful “poo” that photosynthesizers did not need. That is because O₂ is highly reactive, in the sense it creates violent chemical reactions. In large quantities, O₂ could kill the prokaryotes. Fortunately, 3.4 billion years ago, the amount of O₂ in the atmosphere was next to nothing.

But this slowly changed.

Around 3 billion years ago, the numerous photosynthesizers in the oceans were excreting so much O₂ it could no longer just be reabsorbed by rocks in the Earth’s crust as it previously had been. So leftover O₂ entered the atmosphere. By 2.5 billion years ago, the level of oxygen in the atmosphere had increased from next to nothing to about 2.5 percent. This was enough for organisms that had not evolved in an oxygen environment to suffer.

Scores and scores of prokaryotic species (all potential ancestors) died off. This was the single deadliest extinction event in Earth’s history—albeit one that only affected microscopic single-celled organisms. And it is an extinction that living things blindly imposed upon themselves.

It should be noted that this was a slow death. A process that lasted roughly the same amount of time that separates humans from the Cambrian Explosion, or roughly 550 million years. Less complex life, tiny microbes, take longer to evolve and longer to impact the environment. Nevertheless, once felt, life’s power is massive and irrevocable.

Small changes writ large in the Universe—a theme that will continue.

Plate Tectonics

From 3.8 to 3.2 billion years ago, the movement of melted rocks and lava below the Earth’s surface created continual pressure upon a crust that was as thin as an eggshell relative to the Earth’s mantle and core. The immense pressure from all this red-hot movement created flashpoints where gigantic volcanoes exploded out of the Earth’s surface. These giant volcanic plumes may have been responsible for “cracking” the Earth’s eggshell crust.

By 3.2 billion years ago, the regular, uninterrupted flow of plate tectonics began. The Earth’s crust had been shattered into plates that were buffeted about by the flows of lava and squishy rock in the mantle below them. These movements are called convection flows. These push the plates about and constantly change the face of the Earth by moving continents, creating mountains, new oceans, and a deluge of earthquakes and volcanic eruptions.

Imagine a saucepan of clam chowder on the stove. The cool air from the kitchen creates a skin on top of the soup. But liquid is bubbling away below it. If that bubbling gets too vigorous, it may “break” the skin and propel different chunks of it around the top of the pot. That is plate tectonics in a nutshell. Or in a saucepan, at any rate.

The Ozone Layer and the First Snowball Earth

The increase of oxygen in the atmosphere didn’t stop 2.5 billion years ago. It accelerated. Levels of O₂ continued to rise as it gassed out of the oceans. Then, 2.2 billion years ago, it started to enter the upper atmosphere. The heat from the Sun began to transform the O₂ into O₃ in a process called photolysis. This is where the Sun knocks two oxygen atoms apart and then those single oxygen atoms combine with other molecules of O₂ to form O₃. A layer of O₃ began to blanket the Earth. This was the ozone layer. It reflected much of the Sun’s rays, which had previously scorched the surface, back into space.

With little to counteract it, the blanket of ozone got thicker and thicker. With less of the Sun’s heat reaching the surface of the Earth, the whole planet started to cool.

The oceans started to freeze at the Earth’s poles. A thick layer of ice began to form. But it didn’t stop there. The ice sheet began to descend from the poles of the Earth toward the equator. With each movement forward, the snow-covered white ice began to reflect even more of the Sun’s rays back into space. This intensified and sped up the process of plummeting temperatures and the Earth’s freezing. The average global temperature would have been around –58°F (–50°C). Eventually, two massive ice sheets, many meters tall, met at the equator and joined together, encasing the Earth in a tomb of ice. This time is known as “Snowball Earth.”

The Rise of the Eukaryotes

From 2.5 to 2 billion years ago, some forms of microscopic life evolved the ability to use oxygen for energy. This process is called respiration. Instead of converting water and carbon dioxide into energy and giving off oxygen as a waste product, as photosynthesizers do, a respiring or “aerobic” cell takes O₂ and gives off water and CO₂ as waste products. These microscopic single-celled organisms began gobbling up the oxygen in the atmosphere.

Two billion years ago, Snowball Earth placed a strain on all living species. The new oxygen-eaters had to be made of some pretty stern stuff to survive. They evolved into eukaryotes, with a radically more complex single-cell structure than a prokaryote. O₂ actually affords a cell much more energy once it evolves to digest it, so there was plenty of increased energy to fuel this evolution of a “beefier” cell.

The eukaryotes were larger by about 10 to 1,000 times. They were still microscopic, though the largest ones could almost be seen with the naked eye. Unlike in prokaryotes, their DNA was protected by a nucleus. The structure of the cell had a cytoskeleton holding it up (think about tent poles holding up a canvas tent). The eukaryotes were a damn tough domain of various species. They also represented a slight increase in structural and energy complexity. This allowed them to survive the Snowball Earth period.

Eventually volcanoes broke through the sheets of ice covering the Earth and began pumping carbon dioxide back into the atmosphere. This had the effect of warming the Earth. As the ice sheets receded, the carbon dioxide that had been trapped in the rocks of the surface and seabed also began to release CO₂ into the atmosphere. The cycle was reversing itself. The Snowball Earth phase was over—for now—and both aerobic and anaerobic species were able to flourish.

Sexy Eukaryotes

After the retreat of Snowball Earth, the eukaryotes found a thousand new niches opening up for them. Some eukaryotes continued to respire oxygen, using a new organelle (miniature organs within a single-celled organism) called mitochondrion. Other eukaryotes evolved to become photosynthesizers, and instead of mitochondria had an organelle called the chloroplast. The former was the ancestor of animals, the latter was the ancestor of plants. We share at least 30 percent of our DNA with everything in the plant branches of the family tree, whether it be daisies or bananas. We share even larger amounts of DNA with other animals.

Approximately 1.5 billion years ago, some catastrophe and period of ecological strain (the cause of which is unclear) led to a shortage of food for eukaryotes. Perhaps it was a regional crisis, perhaps it was global. But the lack of food began to cause eukaryotes to eat one another, surviving via cannibalism.

This act of cannibalism in a few cases must have resulted in the accidental exchange of DNA. In short, this Hannibal Lecter–esque act was the world’s first glimpse of sex. Up until roughly 1.5 billion years ago, all eukaryotes simply cloned themselves like prokaryotes do. But now some eukaryotes had sex. The evolutionary advantages of sexual reproduction are profound. The exchange of DNA adds a greater amount of genetic diversity. The mutations of DNA are doubled in frequency, and the mixture of genes between two parent cells can also yield advantageous results. Evolution thus can move at a faster pace.

The first “sexy eukaryotes” still divided like cells normally did. But instead of reproducing all their DNA in an exact copy, they would only reproduce half. The cell would then be tasked with finding a “mate” to combine with, in order to complete the number of chromosomes required to create a new organism. Those single-celled organisms that did not find a “mate” died off.

So advantageous was this process to evolution that it spawned a whole new range of tactics and behaviors and, eventually, instincts. Once organisms became multicellular, they began to compete for mates in ways that would influence the evolution of entire species’ behavior. The drive to have sex and reproduce became so engrained in organisms instinctually that it formed one of the primary motives for living: to survive long enough to attract a mate and reproduce. So powerful and pervasive is sex in evolution that it shaped an overwhelming majority of the traits of complex species and the overwhelming majority of their instincts (making organisms rather Freudian as a result), which in the case of humans bled into how we acted, rationalized, and prioritized goals, and even how we shaped our cultures and societies.

The Last Snowball Earth (We Hope)

The trend of photosynthesizers pumping too much oxygen into the atmosphere repeated itself in the last billion years. This grew particularly severe when there was not as much volcanic activity to counterbalance the oxygen by pumping carbon dioxide into the atmosphere. As a result, the last billion years experienced two other phases of Snowball Earth. Not just an Ice Age, but the full encasement of the Earth in a layer of ice. There was one case of it approximately 700 million years ago, and another that began 650 million years ago and ended 635 million years ago.

The final Snowball Earth imposed yet another period of strain on Earth. Those eukaryotes that had evolved to sexually reproduce were able to adapt more quickly to the harsher conditions. Some of these “sexy eukaryotes” came to live in colonies where different microbes filled different functions in a form of symbiosis, which allowed everyone in the colony to survive the freezing conditions.

The last Snowball Earth sent symbiosis into overdrive. Eukaryotes weren’t just living symbiotically in colonies anymore. Each individual set of microbes had become so specialized in their duties in the colony that one kind of eukaryote could not live without the other. Thus, with the pressures of the last Snowball Earth, the first multicelled organisms (the ancestors of plants, animals, and fungi) were born.

Multicellularism

There comes a point where symbiosis between single-celled organisms becomes so intense it crosses the threshold into multicellularism. For example, you don’t just have symbiosis with your liver cells. Your liver cannot crawl along the ground behind you when you go to the shops. It is such an inextricable part of you that you are in fact one structure, one organism.

A multicellular organism is a collection of multiple trillions of cells, each of which is shaped by DNA to act differently, fill a function, and coalesce with similar cells to form an organ. The organs themselves are built up into a patchwork of intricate networks, such as the circulatory system, the respiratory system, and the digestive system.

To give you an idea of the scale of difference, there are 37 trillion cells in a single human body. There are only roughly 400 billion stars in the Milky Way. Thus, there are approximately 92.5 galaxies of single cells in one human body. Complexity in terms of building blocks and intricate structures has gone beyond anything that has been seen so far in our story.

A multicellular organism has a lot more moving parts that can break down. So it is not like there is always an evolutionary incentive for living things to become more complex like this. With greater complexity comes greater fragility. It is why the majority of life on Earth is still single-celled. It is only when a species is forced by the environment to evolve into becoming more complex that it does so.

As a wider rule, the same logic is why the majority of the Universe is fairly simple and most atomic matter is hydrogen. Complexity is in many ways the exception, not the rule. All stretching back to those tiny pinpricks of unequal energy appearing a split second after the Big Bang in a Universe that was already 99.9999999999999 percent equally distributed energy—or dead.

Biological Complexity

In order to create, sustain, or increase complexity, you need energy flows from where there is more energy to where there is less. For an organism to sustain its own complexity and stave off death, it requires greater density of energy flow (for its size) than something like a star.

• The Sun: 2 erg/g/s (a unit of free energy per gram per second)

• A typical microscopic organism: 900 erg/g/s

• A tree: 10,000 erg/g/s

• A dog: 20,000 erg/g/s

While a microscopic bit of organic sludge 3.8 billion years ago would not have been as imposing as a star (it is microscopic and extremely fragile, after all), it requires a great deal more energy for a single cell to maintain all its working parts.

From the first inequalities in matter and energy that emerged after the Big Bang, to stars, to planets, and now to organisms, tiny pockets of complexity are growing brighter and brighter in terms of their energy density. This trend will continue for the rest of our story.

But how is life to meet the increased demand for energy flows? Simple: It must go out and actively find them. While a star is content to float in space for billions of years and simply burn up its fuel, a living being must actively seek out new energy flows in order to sustain its own survival. It does this by chemosynthesizing, photosynthesizing, munching on plants, hunting, or making a trip down to McDonald’s at 2 am after too many beers. You don’t see stars floating round the cosmos, hungrily chasing after fleeing clouds of helium. To actively seek out energy is one of the defining traits of living things.

It also means that at this point in our story, we have a growing sense of historical agency. We are no longer consigned to a passive, inanimate Universe that quietly awaits its fate. We have acquired the ability to grow, to change, to innovate and, where possible, to stave off our demise. Complexity no longer goes gently into that good night.

From this point forward, we fight for survival. And the greater the complexity, the greater the chance that we can win.

chapter 5

Explosions and Extinctions

Wherein multicelled life proliferates in the oceans • Eyes, the spine, and the brain evolve • Plants, then bugs, then vertebrates slowly venture onto land • Extinction events followed by swift evolution create strange and bizarre new species • Complexity plateaus, with boom-bust cycles of Darwinian “tooth and claw”

We now arrive at a more classical vision of evolution. That of “nature, red in tooth and claw” where multicelled organisms evolve and fight for survival. This stage represents an unprecedented level of complexity. While previous changes in our story from the Big Bang to now have been measured in the billions or hundreds of millions of years, evolutionary changes are going to come a lot faster. That is another side effect of higher complexity. Faster rates of change. And more profound impacts on the surrounding environment. In that respect, the last 635 million years have been very eventful indeed . . .

The period of time 635 million to 66 million years ago is primarily characterized by the pattern of explosions and extinctions. An explosion of new evolution as life develops revolutionary new traits that open up thousands of new niches in the environment. Or life rapidly filling old niches left empty by some catastrophic extinction event that killed a large percentage of species on Earth. Each time these things happened, we see the appearance of something new.

But it is important to note that none of that was written in the stars. We could very easily never have evolved. And the entire experiment of life on Earth could have ended with one well-placed asteroid hundreds of millions of years ago. When I consider the hundreds of millions of years of evolution where something different could have happened, or the thousands of human ancestors who might never have survived, or when I add up all those probabilities, in addition to being the one sperm of billions that made it, the fact that I get to exist at all in this Universe makes me feel extremely lucky.

The Darwinian world is by definition a cruel one. Extinction is a necessary component of evolution. In order for the useful traits of an organism to be “selected for” by natural selection, a legion of other competing organisms must cease to exist. There are only so many niches and resources in an environment; 99.9 percent of all species that ever existed have gone extinct. “Natural selection” is a bit of a misnomer; nature doesn’t actively select so much as eliminate everything else.

We are the ones who survived.

The Ediacaran (635–541 million years ago)

After the last Snowball Earth receded, oxygen levels in the atmosphere dropped thanks to volcanoes pumping out CO₂. The climate dramatically warmed as a result. The first multicellular life formed in the oceans. As yet, there was not a scrap of multicelled life on land, which remained as barren and rocky as the surface of Mars.

Fossils from the Ediacaran are difficult to find because most organisms were soft and squishy; they had not yet evolved the carbonate shells and bones that would appear in the Cambrian. The first multicelled species were somewhat modest, and even clumsy attempts at forming a new kind of life. Natural selection had never had to work on such structures before. As a result, they look very outlandish and bear little resemblance to the life that followed them.

For example, in the kingdom of Animalia, there were creatures classified as Ediacara—strange gelatinous structures that look halfway between a coral and a jellyfish. There were also Arkarua, which were strange discs that looked like quilts and sat on the ocean floor. Given their apparent absence of a mouth and anus, they likely absorbed food through their skin and then excreted waste back out in the same way. Then there was Pteridinium, which looked like a primitive worm. And Charnia, which looked like a long underwater fern. Almost all Ediacaran animals didn’t have a means of locomotion, though some may have drifted across the ocean floor “grazing” on what food they could find. It was a weird time. H. P. Lovecraft would have been a fan of the Ediacaran.

Charnia

The Cambrian (541–485 million years ago)

The Cambrian Explosion was a time of very rapid evolution, with multicelled species entering new ecological niches. This process began 541 million years ago and lasted for roughly 15 million years. There are abundant fossils from this time due to the evolution of hard exoskeletons and shells. These were the Arthropods, the ancestors of crabs, lobsters, insects, arachnids, and so on. Either creepy things or the most expensive thing on the menu.

The eye evolved. At first the eye was a primitive sensory tool that animals used to detect changes in light and movement. The innovation stuck, which is why we see eyes across all animals, even when newly evolving species have a declining use for them, such as bats, badgers, or deepwater fish. Eyes did not evolve in the same direction. For instance, many mollusks have eyes along their bodies rather than centrally located in what we would identify as a head. The eyes of ants or spiders are also vastly different to our own. Even in species as closely related as humans and dogs, they each have different aptitudes for sight.

The most successful set of Arthropods were the many different species of trilobites. During the Cambrian, trilobite species ranged between 2 and 14 inches (5 and 35 cm) in size, and fed on a variety of things, from bacteria to vegetation to other animals. They sometimes swarmed in hundreds or thousands. Trilobites would continue to diversify and would manage to hang on to existence until the Permian Extinction 252 million years ago.

Trilobite

The Chordates (our ancestors) had a somewhat humbler start. The first ones evolved 530 million years ago. They started as Pikaia, which resembled a worm and swam like an eel. Pikaia was only an inch (3 cm) long. It had a single rod made from cartilage running along its body. A primitive spine. This was the ancestor of vertebrates. Due to its mode of swimming, one end of the species was always facing the front, to encounter food or danger. This led to cephalization, the process by which sensory organs move increasingly to one part of the body, as such nerves began to make their way along the cartilage to what we would now consider a head. These are the first baby steps of the evolution of the brain. The trend of cephalization continued 525 million years ago with the evolution of Haikouichthys, one of the first identifiable Cambrian jawless “fish.”

Another innovation of the Cambrian era was predation. Anomalocaris, roughly 515 to 520 million years ago, was a vicious Arthropod approximately 3 feet (1 m) in length (dwarfing most other Cambrian life in size). It had an armored exoskeleton, and at the front it had two massive, grasping spiked claws. With these, Anomalocaris would scoop up unwitting prey in the oceans, impaling it on the spikes, and then bring it up toward its downward-facing mouth to be devoured. Hilariously, the name Anomalocaris comes from the roughly translated Latin for “weird shrimp” or “weird sea crab.”

In many ways, predation is just an inevitable evolutionary extension of energy flows in nature. If you can eat solar energy, eat chemicals, eat plants, or eat dead things (as fungi do), why can you not evolve to eat the multicelled creatures that eat all those things? The reason why the impaling and devouring by Anomalocaris looks much more heinous to humans is because we are instinctually driven to avoid being eaten ourselves. The processes of energy flows that we choose to dub either harmless or heinous are made subjectively, shaped by our evolutionary instincts and perspectives. This subjectivity somewhat complicates moral discussions between human omnivores and herbivores and our perspective of the innate cruelty of the Darwinian world.

Anomalocaris

Predation set off an evolutionary arms race. In response to predators such as Anomalocaris, certain species of trilobites began to develop spikes on their exoskeletons in order to discourage others from eating them; other trilobites learned to roll up into balls to protect themselves. Or they developed camouflage and faster locomotion to avoid detection and danger. Other trilobites began to eat worms, jellies, and other unprotected animals that were becoming predators themselves. The evolutionary arms race between predator and prey has continued to this very day.

The Ordovician (485–444 million years ago)

The Ordovician atmosphere was glutted with ten times the CO₂ we have today. In the early Ordovician, the average temperature of the ocean was somewhere between bath temperature and a hot tub—95°F and 104°F (35°C and 40°C), respectively). By 460 million years ago, the seas had cooled to an average temperature of 77°F to 86°F (25°C to 30°C), which is still warm, about the temperature of tropical waters.

The first ancestors of octopuses and starfish emerged. Coral reefs formed in the warm waters. The ancestors of oysters, clams, and sea snails all multiplied. The first sea scorpions emerged, some the size of modern scorpions, some the length of your shin. All told, the number of marine species multiplied by four times in the Ordovician compared to the Cambrian.

Meanwhile, the first multicelled life began to venture onto land. These were the plants. Starting as very simple algae on coastlines and rivers, some of this algae evolved into little weed-like structures that were no more than 4 inches (10 cm) in height. The plants also acted in symbiosis with fungi, which furnished plants with minerals, and became closely attached to their roots.

Mass extinction loomed for the first time since Snowball Earth. Thanks to terrestrial plants, the levels of oxygen on Earth began to increase again, causing a cooling period that killed off warm-water species, but it was short-lived. CO₂ rapidly reached its old levels in the atmosphere, heating the world and killing off the species that had evolved to adapt to the cooler conditions.

In total, 70 percent of marine organisms were annihilated. Their niches were left empty for the survivors to evolve and fill.

The Silurian (444–420 million years ago)

Plants continued their march inland, forming tiny shrubs and mosses. The majority of the Earth was still rocky, with just a smattering of pygmy forests near water sources.

Fungi progressed faster on land. Some of them grew to the height of several meters. While plant roots were primitive and could not yet break into the rocky exterior of the Earth, fungi literally ate into the rocks and flourished during this period.

In the seas, some fish evolved jaws and their spines became more articulated. Jawed fish soon led to the evolution of the first sharks, and the evolutionary arms race continued with other fish developing quicker reflexes and more complex brains.

Silurian jawed fish

Arthropods (bugs, lobsters, and so on) came onto the land in the Silurian. Driven out of the seas by the pressures of the Ordovician extinction event, the first terrestrial Arthropods discovered a food resource in both dead and living plants. For instance, Pneumodesmus lived 428 million years ago and was an ancient millipede about 0.3 inch (1 cm) in length that fed off dead plant material. Not long behind these vegetarian bugs were arthropod predators, most notably the first spider-like arachnids.

The oxygen levels of the Silurian remained quite low, averaging about 15 percent, so these predators remained quite small: only an inch (3 cm) themselves. The Silurian was a world of tiny bugs and tiny plants in a realm dominated by fungus. A somewhat unappetizing image.

The Devonian (420–358 million years ago)

The world was temperate, probably contained little to no polar ice, and was lush and tropical over most of its surface, with the exception of deserts forming at the equator.

Fungi started forming towers and mounds that were up to 33 feet (10 m) high and created increasing amounts of soft soils, which plants could pierce with their roots. As such, ferns and mosses spread into abundance beyond the riverbeds and the Earth finally became a lustrous green.

By 410 million years ago, some plants managed to grow up to 46 feet (14 m) high, and by 380 million years ago, some plant species had evolved wood to strengthen their stems so they could maintain these massive heights or grow even higher as they competed for sunlight. Ergo, the first true forests.

There was a tremendous diversification of species in the oceans. Fish began to grow larger and sturdier, with some reaching between 10 and 23 feet (3–7 m) in length. They developed ray and lobe fins, and more intricate body structures. Sharks became extremely numerous. Sea scorpions grew to a massive 8 feet (2.5 m) long.

Devonian sea scorpion

Spiders began to develop their ability to cast silk webs in order to catch prey. Flying Arthropods appeared during this time and began exploiting the advantages of such mobility. The buzzing began.

The most profound change in the Devonian was the advent of Tetrapoda (or the first vertebrates) on the land. Our ancestors. 380 million years ago, the first lungfish emerged. They had a hole in the top of their head that was angled so that air could flow into primitive lungs. The first lungfish had strong front fins that it could use to drag itself along the bottom of shallow waters in pursuit of food. Gradually this impulse transitioned to dragging itself along beaches. By 375 million years ago, Tiktaalik was breathing air and had strong front and back fins and also primitive hips that would aid with locomotion.

Early tetrapod

By 370 million years ago, we had transitioned to the stem-tetrapods, such as Ichthyostega. About 3 to 5 feet (1 to 1.5 m) in length, this was the first proto-amphibian, swimming in shallow swamps. The skull hole of its ancestors had evolved into nostrils. It had the signature four limbs and five digits of the earliest tetrapods. The same number of limbs and digits are present or “vestigial” to all terrestrial vertebrates. This includes you, frogs, dogs, cats, horses, lizards, bears, and even snakes. In the extreme case of snakes, these vestigial limbs can still be found—having shrunk to be almost imperceptible.

By the end of the Devonian, plants pumped out too much oxygen, cooling and drying out the planet. Amphibians (the only tetrapods) dried out and died. Roughly 95 to 97 percent of them were wiped out. It is astounding to think that the diversity of tetrapod life on Earth today, from salamanders to owls to humans, are descended from a 3 to 5 percent bottleneck. Meanwhile, the climate changes killed off about 50 percent of aquatic life.

The Carboniferous (358–298 million years ago)

Giant carboniferous trees made the oxygen levels reach 35 percent (today’s oxygen levels are 21 percent). The Earth was covered with carboniferous forests. Some of the trees grew to 164 feet (50 m) in height. Because they had pumped so much oxygen into the atmosphere, they were the cause of their own demise. Horrific forest fires were exceedingly common. Large tracts of land dried out and forests could not grow anymore. And this left layer after layer of dead trees, which formed some of the massive coal beds we use today.

The increased oxygen created larger Arthropods. We’re talking giant dragonflies with a 3-foot-long (1 m) wingspan, giant land scorpions nearly 6.5 feet (2 m) long, giant ground-spiders, giant cockroaches, and giant millipedes 6.5 feet long and 1.5 feet (0.5 m) wide. The Carboniferous would be an excellent setting for a time-travel horror film.

Giant insects during the Carboniferous

The first reptiles evolved between 350 and 310 million years ago, and their evolution was intensified after the Carboniferous forests collapsed from a drying climate. Reptiles had tough skin that did not lose as much water. This meant they could head farther inland, away from abundant water sources. Some could even survive in desert climates, which were slowly becoming more abundant. They started laying hard-shell eggs, which meant they did not need to return to the water to reproduce.

The Permian (298–252 million years ago)

The oxygen level shrank to 23 percent, shrinking the size of bugs. The larger kinds required more oxygen to survive. The most successful Arthropods in the Permian were the ancestors of cockroaches, which formed the overwhelming majority of insect biota in the period. Deserts filled with roaches. Yuck.

Reptiles flourished. The ancestors of mammals and dinosaurs in the Permian were synapsids and sauropsids, respectively. The synapsids were protomammals that still looked very reptilian. They used mammary glands to rear their young. Many of them ate roaches. There is no accounting for taste.

Therapsid

The therapsids evolved from synapsids. They were energetic and fast-moving, and as a result they had a higher body temperature. In other words, they were warm-blooded. In order to maintain this temperature, many of them began to develop fur. About 260 million years ago, a smaller group evolved from the therapsids: the cynodonts, which were small, timid creatures, many of which were capable of burrowing.

On the other side of the family tree, sauropsids retained what we would describe as much more reptilian characteristics. These creatures were the ancestors of everything from turtles to crocodiles, to archosaurs, pterosaurs, dinosaurs, and the birds (avian dinosaurs).

The Permian Extinction, or Great Dying, 252 million years ago, is theorized to have been caused by a volcanic supereruption in what is today Siberia. It was a catastrophe that lasted for about a million years. Ash was thrown into the atmosphere, blocking out the sun and killing off vegetation. Acid rain hurtled down from the skies. Oxygen was stripped from the oceans. It was the one mass extinction event that nearly ended all complex life on Earth. This had such a traumatic effect on the planet that roughly 90 to 95 percent of all species died out. The cynodonts managed to survive because of their small size and burrowing behavior. The surviving sauropsids thrived in the new climate and were soon to rule the Earth.

The Triassic (252–201 million years ago)

It was halfway through the Triassic before the biosphere recovered from the devastation of the Great Dying. It was generally quite dry, with massive deserts forming in the interior of Pangea, more arid than even in the Permian era. Rain simply could not reach the interior of the supercontinent.

The sauropsid line had spawned the archosaurs, from which all dinosaurs, pterosaurs, and crocodilians are descended. The archosaurs had an advantage over other reptiles in that they had multiple lungs that allowed them to breathe in an atmosphere with only 16 percent oxygen. Dinosaurs at the start of the Triassic were only a small minority. Roughly 5 percent.

About 234 million years ago, volcanism increased the climate and humidity of Earth. Rain was suddenly everywhere. In this “pluvial episode,” rain belted down across the Earth for 2 million years straight. This had a devastating effect on animals that liked the arid desert climates. Meanwhile, dinosaurs thrived in the more humid environments that emerged. The first pterosaurs began to take flight.

The Triassic extinction event 201 million years ago (its cause is unclear—but probably an asteroid) wiped out a great many amphibians, therapsids and most archosaur species other than dinosaurs and pterosaurs. As a result, dinosaurs came to represent 90 percent of all tetrapods on Earth. Protomammals cowered on the fringes.

The Jurassic (201–145 million years ago)

The Jurassic opened with the supercontinent Pangea cracking into pieces and the climate becoming increasingly humid. The modern continents began to take form, with North America and Europe merged together and South America and Africa still connecting their perfect “puzzle pieces.” The gulf was increasing between these two continental couples. As a result, there was no longer a huge desert interior. Rainfall hit more of the land, which increased the amount of forest and heavy vegetation. The oxygen levels increased to approximately 25 percent.

Dinosaurs filled the empty niches left by the Triassic extinction. The humid rainforests afforded herbivores a great deal of food, and the dinosaurs evolved to eat increasing quantities of vegetation. Thus, we see the evolution of species like Supersaurus, which was 115 feet (35 m) long, and Allosaurus (33 feet/10 m in length and a classical-looking dino predator) dominating the food chain.

Protomammals kept out of the way. Their average size was not much bigger than a mouse. They burrowed or hid up trees, ate insects, and only came out at night. By 165 million years ago, a few of them became tree-bound and developed gliding abilities, and a few returned to the coastlines and habitats closely attached to water.

By the Late Jurassic, the first avian dinosaurs (the ancestors of birds) began to take flight. A sort of fuzz appeared on just a few Triassic dinosaurs for warmth and this now became feathers. Some dinosaurs remained coated with primitive feathers (even T. rex in the Cretaceous may have had fuzz), some dinosaurs had no feathers at all, but in some species feathers spawned flight.

The Cretaceous (145–66 million years ago)

The break-up of Pangea was complete. North and South America drifted slowly toward each other. Australia, Antarctica, and India broke off from Africa, the latter set on a collision course with the belly of Eurasia.

Oxygen levels rose to 30 percent. On an Earth still dominated by dinosaurs, certain corners of the biosphere were beginning to look decidedly more “modern.” Grasses evolved for the first time. It is odd to visualize, considering how much of the Earth is covered with the stuff, but they had not existed in the masses of vegetation in the greenest phases of the Earth before, whether Carboniferous or Jurassic.

Around 140 million years ago, ants emerged. They are one of the most common and adaptable species of the biosphere, accounting for roughly 20 percent of the Earth’s biomass today.

Then, 125 million years ago, flowering plants (which had not existed before) evolved and spread across the Earth, largely thanks to their concurrent evolution with bees.

Around the same time, the first proto-placental and protomarsupial mammals appeared on the fossil record. Both gave birth rather than laid eggs, with the former species gestating the offspring for longer in the womb and the latter giving birth and nurturing the offspring in a pouch or pocket. While still quite small and skittish, the placentals would become prominent in the Americas, Eurasia, and Africa, and the marsupials would predominate in Australia. And the ancestors of the platypus laid eggs, confusing the hell out of everyone.

Meanwhile, the dinosaurs continued to reign supreme, with most niches being filled by them. This glut of dinos stiffened competition between species—particularly in terms of the balance between herbivores and the predatory carnivores that hunted them. As a result, you get some of the most astounding forms on both sides in this period—from the emergence of apex predators such as Tyrannosaurus rex and Albertosaurus to the increasingly diverse defensive tusks used by Ceratopsia like Triceratops, the long spines that sauropods grew on their necks to ward of predators, as with Amargasaurus, or the heavy armored plating worn by Ankylosaurus.

Ankylosaurus

An extinction event during the Cretaceous obliterated 70 percent of the remaining species on Earth, including 90 percent of terrestrial animals and 50 percent of plant species. An asteroid 6.2 miles (10 km) in diameter struck the Yucatán Peninsula. Worldwide earthquakes, tsunamis, continent-wide forest fires, and huge torrents of acid rain killed off much life. Then all the dust flung into the air blocked out solar energy and killed more plant life, causing the surviving herbivores to starve, followed by the carnivores. The Earth became littered with rotting plants and animals, fed upon by flies, maggots, and other corpse-feeders. Those birds and mammals that could eat insects and survive on what little plant life remained escaped the catastrophe, while non-avian dinosaurs perished. The niches had been swept clean once again, and this time it would be the mammals that would fill them.

The period of multicelled organisms from 635 to 66 million years ago only saw slight increases in complexity overall. In fact, during this period complexity more or less plateaued. The Darwinian game of evolution and extinction might have been the height of complexity in the known Universe. Except by a series of accidents in a world dominated by mammals, a new and faster form of evolution would emerge, capable of achieving even higher levels of complexity: culture.

chapter 6

Primate Evolution

Wherein mammals fill the niches left empty by the dinosaurs • Primates evolve bearing decidedly familiar traits • Humans split off from our last common ancestors with the Great Apes • We start walking on two legs and our brains get bigger • We start accumulating more information with each generation than is lost by the next

Sixty-six million years ago, the world was a wasteland. Chilly and dry. The landscape was littered with dead plants and animals, rotting away in the sun and gradually being covered by layers of dust and dirt. Large species had been heavily hit in the Cretaceous extinction event, because of the collapse of the food chain. Aside from turtles and crocodiles, the land was now populated by tiny creatures like birds and mammals.

The boom-bust cycles of biological evolution continued as they always had. The ecological niches of the world had been swept clean. A rapid evolution of mammals filled them again. At first, mammals resembled mice or chipmunks. They were mostly under 1.5 feet (50 cm) long and weighed under 2 pounds (1 kg). They nibbled on plants and ate bugs. They burrowed into the ground to hide or concealed themselves in trees. These mammal survivors would diversify and dominate the Earth as the dinosaurs, Sauropsids, amphibians, and Arthropods had done before them. And the vicious Darwinian cycle might have continued without any sign of increasing complexity for hundreds of millions more years. But this time there was something new on the horizon . . .

By 60 million years ago, the climate had warmed up again. The world was warm. North America and Eurasia were tropical. The majority of the Earth was covered in forests, with deserts at the equator. At the poles, there was little or no ice. And the mammals had begun to grow.

The ancestor of elephants at this time was no larger than a dog, but it would gradually evolve to become the world’s largest land mammal. At the same time, a similarly sized mammal had begun to hunt fish and red meat, using sharp teeth for tearing the flesh of prey. By 42 million years ago, these predators had evolved into two branches with canine and feline characteristics: the ancestors of wolves, foxes, and bears or lions, tigers and jaguars, respectively.

Fifty-five million years ago, a small mammal the size of a cat evolved to periodically spend time in the water and even submerge itself. This mammal was the ancestor of hippos and whales. The ancestors of whales began to spend more and more time in the oceans, first in shallow waters, later being able to dive deeper and eat scores and scores of krill and fish. By 40 million years ago, their transformation into whales was complete.

Also 55 million years ago, the ancestor of the horse—multi-toed and around the size of a dog—dwelt in the forests. It crept quietly and nimbly among the trees and the brush on the forest floor. Once the climate cooled and dried, these creatures began running increasingly on the dominant third toe. Over time, the other toes receded significantly, giving horses their characteristic hooves. They no longer crept through the forest but traveled vast distances.

Ancestral horse

In a relatively short amount of time—a few dozen million years—mammals rapidly filled environmental niches and grew from tiny sizes to form the bulk of the world’s megafauna and the building blocks for the familiar species we know today.

Fifty-five million years ago was also when the primates emerged. They began as small tree-dwelling mammals with grasping hands and front-facing eyes. These traits were particularly useful to avoid tumbling from the trees. The front-facing eyes, for instance, permitted primates stereoscopic vision and depth perception, which is particularly crucial when judging a leap from one branch to another. In order to process all that 3D information, primates required increasingly larger brains.

Primates colonized the Americas and, separated by the vast Atlantic 40 million years ago, they continued to evolve there into the New World monkeys. They had flatter noses and side-facing nostrils, longer tails useful for grasping things, and most species did not have opposable thumbs. New World monkeys were also more likely to observe monogamous relationships.

Conversely, in most species of Old World monkeys, polygynous relationships were most common. Females of most species stayed with their mothers for life, while the males grew up and found their own harem of females, chasing off all other males in extremely aggressive displays.

Old World (common chimpanzee) and New Norld (red-faced spider monkey) primate faces

In Africa, 25 to 30 million years ago, the line of the Great Apes diverged from the Old World monkeys. Great Apes were the ancestral species of chimpanzees, bonobos, gorillas, orangutans, and humans.

Within primates are instinctual traits that humans retained or discarded. Figuring out the ones we retained can tell us a lot about what lies at the core of our own evolutionary wiring, which underlies many (if not all) of our actions and how we build our societies.

“Gorilla Warfare”

Humans split off from the evolutionary ancestors of gorillas about 10 to 12 million years ago. While gorillas may look threatening, most gorilla aggression comes in the form of intimidation and displays, though they can make a very good job of defending themselves if mere threat doesn’t cover it. By and large, it is warfare by bravado.

Gorilla hierarchies typically have female gorillas stay with the same group for life, while male gorillas are driven out by the leader of the group, the silverback, when they come of age, to wander as bachelors until they can construct female-populated groups of their own or supplant an existing silverback of another group. Male competition led to a high degree of sexual dimorphism, an evolutionary process where notable sexual differences gradually appear between biological sexes, with male gorillas being significantly larger on average than the females. Male gorillas also tend to kill infants that they did not sire, in order to increase the chances that their own DNA will become dominant instead.

Female gorillas make sure to form relationships with males to gain protection from these predators, not to mention the protection of their young from infanticide. Females that are kith and kin tend to stick together in sisterhood, being very supportive of each other’s interests and safety. Female gorillas that are not related tend to compete aggressively.

Male gorillas are more likely to be hostile to each other, even when they are related. Competition and hostility are more common. With one notable exception. When male gorillas have been booted by a silverback from a female-populated group, they sometimes band together rather than roaming around solo, and when in exile they are much friendlier to one another, even engaging in mutual grooming and friendly wrestling. Some gorillas even eschew the harem completely and engage in the occasional bout of gay sex.

Our Closest Cousins

Chimpanzees are our closest surviving evolutionary cousins. We share 98.4 percent of our DNA with them. We split off from chimps through a last common ancestor about 5 to 7 million years ago. Chimps are smaller than humans, about 3 to 4 feet (100–120 cm) in height. But they are typically much stronger and more aggressive. Chimps have a brain that is three times smaller than a human’s. Nevertheless, we can see a lot of similar instincts and behaviors in them. Not to mention inventiveness, genius, and group politics. Chimps eat plants and insects, and not infrequently they are sighted hunting colobus monkeys. Males go around in packs to gain access to this food and to protect their territory from other groups of chimps. It is likely that territoriality is a trait passed down from our last common ancestor with chimps, but that sort of behavior is hardly unusual in animals. What is novel is the organized way chimps do this.

Unlike gorillas, it is entirely common practice for chimp groups to be composed of a collection of males with a leader and a corresponding group of females, which also arrange themselves in a hierarchy. The leader of a chimp group can be the strongest and most aggressive, but not always. The chief must also be the most manipulative and savvy at maintaining alliances to support his rule. A chimp Machiavelli. As a result, it is sometimes the case that the leader is not the biggest bruiser per se, but a leaner, weaker politician who has managed to convince others to do his bidding. Other males have been known to team up and launch a violent revolution that overthrows and replaces the leader. This looks decidedly more like human politics.

Females have their own firm pecking order: Some dominate, others submit to other females. The female dominance hierarchy also extends to offspring. Aggression toward a high-ranking daughter, even while she is young and weak, is punished by the dominant mother and her allies. The daughter is thus protected until she reaches the point where she can start forming dominance alliances of her own. There is a whisper of the hereditary principle in this behavior, where one can gain additional privileges in a hierarchy because of who your parents are.

Meanwhile, chimp male dominance is entirely dependent on acceptance by the hierarchy of females. If they don’t like you, you cannot be the group’s leader. If you are already the leader and females turn against you, they will help to overthrow you and put a new male in your place. Even this has echoes of the “soft power” held by elite women (such as Roman empress Livia Drusilla) in human history before modernity.

If you are higher up in the hierarchy, you get priority access to mates and food. Chimpanzee hierarchies are noticeably complex relative to these of other primates, and a larger brain was required by evolution to cope with all the social interactions necessary to maintain alliances.

Like many primates, chimps use tools. They fashion sticks to fish termites out of the ground for food. They use rocks as hammers. They use leaves as sponges to soak up water. They use branches as levers. They even fashion banana-leaf umbrellas. These techniques are taught, passing from adult to child. This counts as a form of social learning. Even a form of culture. They do not, however, build on these inventions generation after generation. Otherwise, over 5 million years chimp “termite fishing” would doubtless have reached an industrial scale.

Chimps have language. Most chimp communication is carried out by gesture, but they do have a limited range of vocalizations. The limit is imposed by the chimp’s physiology restricting the range of noises they can make and also their brain capacity. In captivity, chimps have shown a remarkable aptitude for memorizing a wide range of written symbols.

Chimpanzees can also be highly violent. Male chimpanzees band together, roam their territory and see if they can find a lone chimp to beat up. They set about kicking and hitting the lone chimp. It is common practice for chimps to start tearing off bits of flesh—particularly the ears, bits of the face and, most shockingly, the genitalia. Warfare among chimpanzees is not a thing. They don’t have the numbers or the coordination. But they are perfectly happy to patrol their territory and brutalize strangers. Coordinated violence on out-group individuals certainly is a trait held in common with humans.

Bonobos

Chimpanzees are male-led and quite aggressive, because sex is distributed according to hierarchy. In dramatic contrast is their close cousin (and ours) the bonobo. Approximately 2 million years ago, two groups of ancestral chimpanzees were separated into different environments by a growing Congo River. The chimps to the south (which became bonobos) evolved radically different habits. Bonobos live in a female-led hierarchy where sexual activity is rife. Males are often physically stronger, but on the very rare occasion where a male shows aggression toward a female, a sisterhood of bonobos gang up on him and put a stop to it. Sometimes they scare him off with hoots and shouting. Sometimes they break his fingers. Females can also be violent toward each other when enforcing the hierarchy. But overall violence is a lot less due to the profusion of sex.

Rare for most primates, bonobos can have sex “face-to-face,” engage in fellatio and cunnilingus, and perform “French kisses.” Bonobos are highly sexed and masturbate every few hours. When greeting each other, bonobos have a tendency to touch each other’s engorged genitals in what is referred to as a “bonobo handshake” in order to reduce initial tensions. Because sexual activity is more common in bonobo groups, there is less reason for male aggression in the first place. When two groups of bonobos meet in the woods, the males in the group might get a little tense at first, but then the females from the two groups cross over and start having sex with the strange males. The intergroup tension, which among chimps would lead to fighting, ends in an orgy among bonobos.

It is therefore perhaps unfortunate that humans are more closely related to chimpanzees than bonobos. But while aggression, war, and male competition are all present in humans, we seem to share a lot of sexual habits with bonobos and we even engage with “make love, not war” on occasion (though relative to instances of “making war,” the more hippie periods of human history are considerably rarer).

But what is open to question is how many of the familiar chimpanzee traits humans inherited from their last common ancestor and which ones were culturally invented by humans much later. If the more negative aspects of human societies are founded on evolutionary wiring, they might never be expunged. If they are culturally derived, then they can be unlearned in the space of a generation or two. So one must also ask: How did we continue to evolve in the 5 million years that separate us from chimps?

Bipedalism

Five million years ago, our ancestors still dwelt in African forests. Our last common ancestor with chimpanzees walked on the ground with bowed legs, using its arms on the ground for balance. It was better suited for quickly climbing trees to avoid predators (of which there were many in Africa) than for covering long distances on flat ground.

Four million years ago, the climate entered one of its dry phases. The forests shrank back, leaving woodlands and eventually the wide, open savannah of East Africa. Primates that ventured away from the forests to find food could no longer scamper up trees for safety and they had to range farther and farther to find food. As a result, our ancestors started to walk upright on two legs, evolving bipedalism.

Some of our first bipedal ancestors, the Australopithecines, were short, standing only about a meter tall, or just above three and a half feet. They looked a lot like chimpanzees, only bipedal. Australopithecines were largely herbivores, with teeth adapted for grinding tough fruits, leaves, and other plants (which humans have inherited despite our later adoption of meat-eating). They may have occasionally scavenged meat from corpses, but they weren’t really equipped to consume raw meat and did not yet have control of fire to cook it.

Because Australopithecines were bipedal, this freed up their hands for regular use of an even wider range of gestures, widening their range of language. Most communication happened by gestures and facial expressions, rather than vocally via grunts and yelps. Even today, many anthropologists and psychologists assert that the vast majority of human communication still happens via subtle gestures communicating sophisticated emotions and mental states, rather than by words. Free hands also allowed Australopithecines to carry tools and transport them from place to place. Enhanced language and more regular use of tools put evolutionary pressure on Australopithecines to increase their brain capacity to keep up.

“Lucy,” one of the oldest-known human ancestors

Homo habilis

By 2.5 million years ago, Homo habilis evolved. Homo habilis did not stand much taller than Australopithecines, and their brains were only slightly bigger. But there seems to have been an increase in intelligence and inventiveness. Homo habilis were known to have hit flakes off stones to use them for cutting. And making stone flakes is difficult. Human archaeologists have tried to reenact this activity and it is tricky, requiring a lot of trial and error. It requires some pretty beefy intellect, intentionality, and the patience of a craftsperson. But there were limits. As important a breakthrough as stone-working was, we see very little sign of technological improvement over the million years that Homo habilis existed. We see invention. But we don’t see the accumulation of invention generation after generation to make those cutting implements better or more diversified.

As for the social complexity of Homo habilis, it was arguably similar to that of Australopithecines or chimpanzees. Their groups remained quite small. But 2 million years ago, population growth caused Homo habilis groups to run into other groups more frequently. This put pressure on the brain to manage more frequent and complex social interaction, including alliance building, so that violence would not break out every time groups met. Strategies included gift-giving and intergroup marriage. The latter was particularly effective, since it prompted two groups to have an interest in the continuation of a combined line of DNA. It is around 2 million years ago that evolutionary anthropologists estimate that monogamy (long held by New World monkeys) began to evolve in our own family tree in Africa. The fact that Homo sapiens have both successful and unsuccessful attempts at monogamy, in addition to polygamy and promiscuity, is testament to two strands of evolutionary wiring being in conflict with each other.

Another way primates bonded with each other and formed alliances was by grooming: picking the bugs and dirt out of someone’s hair. We see this in our last common ancestors with Old World monkeys, going back 40 million years. But as group numbers grew, we couldn’t groom everyone. There wasn’t enough time in the day. So we began to “gossip” or small-talk.

Homo habilis still had a very restricted range of sounds to form speech. But gesture allowed some communication, added to which they used pleasing sounds such as hums, grunts and yells to convey displeasure. There was an evolutionary advantage to socializing, putting selective pressure on these communication abilities to grow.

This may have been reinforced by sexual selection. Females may have chosen males who were able to express themselves in ways that either charmed them or convinced groups to follow them. Since the last common ancestor with chimps 5 million years ago, mating preference had been given to those males who were able to form alliances and ranked high in the group.

The pressure on enhanced communication to deal with growing social complexity had a profound impact on brain growth, which manifested in our next major ancestral species.

Homo erectus

About 1.9 million years ago Homo ergaster-erectus evolved. There is debate over where both ergaster and erectus should be classified in a single species that looks pretty similar. Homo ergaster usually refers to the earliest versions of the species that existed in Africa, while Homo erectus refers to the species as it traveled across the Old World. For simplicity, I will simply refer to both as Homo erectus. But this is not a position on the current debate about the taxonomic classification.

Homo erectus was taller than Homo habilis. It had perfected the art of bipedal locomotion. Homo erectus was definitely more comfortable crossing long distances than Homo habilis. In fact, Homo erectus would present a challenge to human bipeds today in stamina and running speed. Their facial structure looked far more human; if you saw one wearing clothes on a bus you might be forgiven for not really noticing anything unusual about them. Their body hair had receded significantly from that of earlier primates, leaving melanin of the skin protecting them from the African sun’s harsh rays. In fact, in most major phenotypical aspects, Homo erectus was exceedingly human.

There is some evidence that Homo erectus lived in larger social groups than earlier ancestral species, and encountered other groups more frequently. There is also evidence that they had controlled use of fire and were able to cook and eat meat. The consumption of meat was crucial to further brain development, since it packed more energy in a single morsel than a comparatively larger amount of vegetation. The most notable aspect of Homo erectus is that they had a decidedly bigger brain, roughly twice that of Homo habilis and 70 percent that of modern humans.

Homo erectus

A population boom led Homo erectus out of Africa and across southern and eastern Asia. They adapted to deserts, forests, and coastal and mountain regions. A species this adaptable certainly had to be advanced in intelligence. They became the first pan–Old World human species and they continued to exist for hundreds of thousands of years.

The First Collective Learning?

There was very little technological improvement in the toolkit of Homo erectus in the first millennia after it evolved 1.9 million years ago. Then, 1.78 million years ago, Homo erectus invented a new kind of teardrop axe in East Africa. This could just have been a one-off. For thousands of years Homo erectus did not tinker with or improve this tool. That was in keeping with every primate tool-user before them. Chimps, Australopithecines, and Homo habilis were all bright enough to come up with new tools and to pass the techniques on to their offspring, but not to improve them generationally.

Yet with Homo erectus 1.5 million years ago in East Africa, we see the first glimmer of evidence of a revolutionary new ability. Homo erectus began to improve their hand-axes in quality, and converted them into multipurpose picks, cleavers, and other kinds of implements.

This is hugely important in our story. It was the first sign of tinkering, accumulation of innovation, and improvement of technology generation after generation. Something known as collective learning.

Why does this matter? If there is a limit to how much one can invent, a species more or less stays the same for thousands of years until biological evolution changes them. Even with tool use, they are still stuck in the slow process of natural selection in order to raise complexity. However, if a species like Homo erectus could improve on existing technologies by tinkering with them—and with no major genetic change or evolution—and also spread out from their traditional habitats across the world, this is the sign of something new. It means this species was no longer dependent on biological evolution or the cruel Darwinian world to increase its complexity.

We have made the first tentative steps into the “cultural realm,” where the complexity-generating process of collective learning blazes along at a faster speed than biological evolution. Like express highways built atop older winding roads.

And collective learning had only just begun to evolve. A trickle would soon become a flood.

part three

The Cultural Phase
315,000 years ago–present

chapter 7

Human Foragers

Wherein Homo sapiens evolve from a long lineage • Collective learning is more powerful than ever before • Roughly 25 billion of us live in foraging communities spread over 98 percent of human history • A genetic bottleneck reduces our gene pool to less than 10,000 individuals • Shortly thereafter we migrate across the world

Accumulation. That single word, more than any other, sums up what makes Homo sapiens different. The ability to accumulate more information with each generation than is lost by the next, also known as collective learning. Humans didn’t get to where we are today because we are all super-geniuses. A cursory glance at politicians, celebrities, or perhaps your in-laws is proof enough of that. A human raised alone in the wild would not have any remarkable advantage over other animals. Also, humans can only invent so much stuff in a single lifetime—when they’re not too busy trying to survive, that is, which most people were throughout the majority of history.

Yet with generation after generation of invention, humans became something novel and unique in the biosphere. Like building blocks laid one upon the other. Slowly but surely, inventions stacked up, leading to dramatic changes in complexity within a few thousand years. In the blink of an eye in evolutionary time, humans have gone from stone tools to skyscrapers. That is the power of collective learning.

Isaac Newton said he stood on the shoulders of giants when it came to his own work on gravity (although, arguably, this was just rhetoric to cover up plagiarism). In reality, the “giants” are actually composed of thousands and millions of inventors throughout human history. That is why the ability to accumulate innovation is what makes humans so unique. More so than just our raw brainpower or capacity for language and abstract thought. We have an unparalleled talent for remembering details of the past. Remembering our history.

From Homo erectus to Homo sapiens

Homo erectus showed the first sign of collective learning 1.5 million years ago. It was a very humble start. Homo erectus took tens of thousands of years to make moderate improvements to their stone axes. Nevertheless, collective learning had appeared in our evolutionary repertoire. Provided natural selection considered collective learning useful to survive, the skill would only grow more powerful with each new species.

Homo antecessor evolved 1.2 million years ago and moved into Europe in large numbers, requiring innovation to deal with the frigid and foreign environments there. They were about the same size in terms of height and body weight as Homo sapiens, but they had slightly smaller brains and a much more limited form of language.

Homo heidelbergensis evolved about 700,000 years ago in Africa and slowly spread over Europe and West Asia. They had even larger brains, which could fall roughly on the low end of the human average. It is likely they had a fairly acute sense of being able to distinguish sounds in speech, like modern humans, and a pretty intricate form of communication.

The Neanderthals appeared approximately 400,000 years ago and had brain sizes that rivaled that of modern humans, though they appear to have had limited capacity for abstract thought (contemplating and communicating things that aren’t actually there).

Homo antecessor, Homo heidelbergensis, and the Neanderthals all show clear signs of collective learning. They presided over the first systematized and regular use of fire in hearths, the first blade tools, the earliest wooden spears, and the earliest use of composite tools where stone was fastened to wood. Homo heidelbergensis became the first hominine to colonize all of Eurasia. Neanderthals even adapted to climes that made clothing and other cultural innovations necessary for insulation and warmth. They manufactured complex tools, with prepared stone cores, producing a variety of implements—sharp points, scrapers, hand-axes, wood handles—with deliberate use of high-quality stone materials, and countless variations and improvements over time. All this invention and expansion across the Old World is a clear sign of collective learning growing evolutionarily stronger.

Then, 315,000 years ago, people that were anatomically identical to Homo sapiens first appeared in Africa. Why did Homo antecessor, Homo heidelbergensis, and the Neanderthals all go extinct while Homo sapiens did not? Simply because Homo sapiens was the most talented at collective learning. For example, once Homo sapiens entered regions already populated by the Neanderthals, we outcompeted them for resources, likely killed many of them and notably also interbred with them (outside of Africa, a substantial amount of our DNA today includes Neanderthal genes).

Homo sapiens had the most advanced collective learning, the most diverse toolkits, and were the most adaptable to new environments. We had big brains, a greater capacity for language, and we were more capable of abstract thought, as evidenced by the fact that we alone painted cave art, used body paints, played music, wore decorative jewelry, and demonstrated symbolic thinking. All of these traits complemented our capacity for collective learning as we built up huge knowledge bases about how to forage and survive in the hostile environments of the Paleolithic Earth.

Collective learning has two main drivers that make it stronger the more they are enhanced.

1. Population numbers: The number of potential innovators in a population. Not all of them will conjure an improvement in technology, doctrine, or philosophy in their lifetimes. But the more people you have, the more rolls of the dice there are to increase the probability that one of those people will come up with either a minor or major innovation.

2. Connectivity: In order to build on the ideas of the past, humans need access to them. This means either access to repositories of oral or written knowledge or communication with other humans who possess that knowledge. Perhaps even collaboration with them.

While today, with instantaneous communication via the internet and the equivalent wealth of knowledge of the Great Library of Alexandria being available on your phone, it is difficult to imagine what limitations in connectivity might have imposed on innovation. But for the majority of human history, one of the biggest things holding innovation back was access to the pool of wider human knowledge. For the first 300,000 years of our existence, our communities were limited to a few dozen foragers.

As we shall see, much of the story of human history is the intensification of both population numbers and connectivity, and the resulting acceleration. Look at how little humans have changed biologically over the past 10,000 or even 100,000 years. But consider how vastly our lifestyles have shifted in the same space of time. Everything is accelerating.

How do we assign a date for the start of Homo sapiens? First, there are the Omo remains, discovered in East Africa between 1967 and 1974. Radiometric dating puts the oldest of these remains of anatomically identical Homo sapiens at 195,000 to 200,000 years old. Then, in 2017, we discovered more Homo sapiens remains in Morocco, dated to approximately 315,000 years ago or older. So currently, 315,000 years old is the best supported start date for our species. But this number could grow larger in the coming years if new discoveries are made.

It is unlikely Homo sapiens underwent a rapid genetic change subsequent to 315,000 years ago that significantly enhanced its intellect or capacity for collective learning. They were using decorative beads in Africa prior to the Second Great Migration 64,000 years ago, mining for new materials 100,000 years ago, fishing 120,000 years ago, and using body paints around 300,000 years ago. So we’ll be operating on the assumption that anatomically identical Homo sapiens started 315,000 years ago, with only minor genetic changes (such as skin color, hair color, eye color, and much later lactose tolerance and varying tolerances for alcohol) in the subsequent millennia. But no change was so profound that it required classification as a different species or subspecies.

Stone Age Humans

We now properly enter the realm of human history. For the majority of human history—an estimated 95 to 98.5 percent of our entire existence—we dwelled in small groups of foragers, ranging across the Earth hunting and gathering food. The historical actors in this part of the story were anatomically identical to modern humans, with the same range of emotions and capacity for invention that we possess today. As such, it’s easier for us to feel empathy with those in this part of the story than the living beings of earlier periods. These people were us. If we had been born in that era, we would have behaved the same way. But human foragers lived very different lifestyles, in a world hit with ice ages and populated by a terrifying range of megafauna, from saber-toothed tigers to carnivorous 10-foot-tall (3 m) kangaroos. The past is indeed another country, if not another planet.

Taking the 315,000-year date as our starting point, approximately 100 billion humans have lived and died on the surface of the Earth since the origin of our species. Of those, 16 to 20 billion have lived since the start of the Industrial Revolution 250 years ago, with about 8 billion alive today, at the time of writing. An additional 55 billion are estimated to have lived between the beginning of agriculture 12,000 years ago and the Industrial Revolution. That’s 71 to 75 billion people out of 100 billion.

That leaves approximately 25 to 29 billion people who lived between 12,000 and 315,000 years ago—the foraging era. For the majority of that time, most humans lived in Africa, and only in the past 64,000 to 100,000 years have a substantial number of humans lived in the rest of the world. We know that the Earth can only support about 6 to 8 million foragers living at any given time. For the overwhelming majority of the Paleolithic, our numbers were a lot fewer than 500,000.

Biologically and instinctually speaking, humans are best suited to the foraging lifestyle. It is what we were wired for. All the vast changes of the past 12,000 years since the invention of agriculture have not left enough time for us to evolve and catch up.

In short, we are cavemen in fancy shoes.

The Ice Ages

The past 2.5 million years have seen numerous waves of cooling and heating, with long glacial periods (ice ages) interspersed with so-called interglacial periods (such as the one we are in now). There have been two or three ice ages since Homo sapiens evolved in Africa 315,000 years ago. During an ice age, large parts of North America, Europe, and Asia are covered ice sheets, the average global temperature drops, previously lush climates in other regions of the world such as Africa dry out, and the sea level drops.

The second-to-last ice age started 195,000 years ago, when Homo sapiens were alive and well in Africa. It continued for a further 60,000 years, until an interglacial period began 135,000 years ago. This interglacial lasted for just 20,000 years, until approximately 115,000 years ago (interglacial periods are generally shorter than glacial ones). The “Last Glacial Period” began 115,000 years ago and it was a particularly long one, lasting just over 100,000 years. It was in this world that humans migrated out of Africa and across the Earth.

The world at the Last Glacial Maximum

At the height of the last ice age, about 30 percent of the Earth’s terrestrial surface was covered with ice. Where ice sheets did not spread, colder temperatures made forests turn to woodland or even deserts. Winters lasted longer than they currently do. While most humans 115,000 years ago lived in Africa, the conditions there were much more frigid than those experienced in Africa today.

The Genetic Bottleneck

Homo sapiens’ foraging method of finding food remained the same for thousands of years: Roam a territory hunting and gathering until the flora and fauna of the region become depleted, then move onto another region while the previous one naturally replenishes itself. Using this method, the entire surface of the Earth can support only 6 to 8 million foragers.

As human populations in Africa grew, they needed to find more food to support them. The answer to this problem was not to intensify the amount of food produced in Africa but to “extensify”—by traveling farther and farther afield.

This may have prompted the First Great Migration of humans out of Africa 100,000 years ago into the Middle East, with some indications that they reached as far as India. These regions were still out of reach of the ice sheets. Despite this migration, the vast majority of humans remained in Africa.

We have indications in our DNA histories that human genetic diversity shrunk dramatically before the Second Great Migration. One possible explanation is the supervolcanic eruption that occurred during this period at Mount Toba 74,000 years ago. In the middle of the island of Sumatra, in present-day Indonesia, was a volcano. Where this volcano once stood there is now a lake. Or rather, a crater.

Mount Toba exploded with the force of 1.5 million Hiroshima-size bombs and with the force of the nuclear arsenals of every single country in the world today. Multiplied by at least three. The eruption threw an unprecedented amount of rock into the atmosphere, scattering rubble and magma far and wide on a continental scale. A layer of volcanic ash, an average of 6 inches (15 cm) thick, settled over everything in South and East Asia, but also in India, Arabia, and as far as East Africa. Much more ash was flung up into the atmosphere, darkening the skies and obstructing sunlight in an era already beset by an Ice Age. What followed may have been a decade of perpetual winter for the entire globe. It may well have reduced the population to 10,000 people. Or even as few as 3,000.

In the past decade, the Toba hypothesis has been disputed by several scientists. I am still waiting for an alternative explanation for the bottleneck that is evident in our DNA. Hold on for the second edition!

Regardless, the genetic bottleneck tells us something very important about race. In a nutshell, humans today come from at most 10,000 people only a few tens of thousands of years ago. That is not enough time for significant genetic differences to occur between ethnicities. In fact, compared to other primates, modern humans today have an extremely low amount of genetic diversity. There is more genetic diversity between two groups of chimps separated by a few hundred miles than in the entire human race. We are not exactly an inbred species, but we are all pretty damn closely related.

The Second Great Migration

By 64,000 years ago, we headed out of Africa for a second time. Humans spread from Africa through the Middle East, down into India and Indochina within just a few thousand years. By approximately 60,000 years ago, humans had figured out how to use the land bridge that existed in Indonesia at the time (due to lower sea levels from the Ice Age) to make their way by foot and by rafting into Australia.

Stone-age seafaring is no easy task. The entry of humans into Australia is the foraging equivalent of landing on the Moon. Humans gradually spread across Australia over the next 20,000 years, heading into Tasmania by 40,000 years ago via another land bridge.

Also around 40,000 years ago, humans went north into colder climates, crossed the Caucasus Mountains and entered Russia, quickly making their way into Europe from the east. Most impressively, humans continued to spread into increasingly colder climates, and were in ice-age Siberia by at least 20,000 years ago. Consider the survival skills necessary in such an environment.

Human migration 200,000–12,000 years ago

The entry of humans into the Americas requires a more searching statement. We are less sure exactly of how people got there. It seems clear that humans would have crossed the Bering Strait (which was then yet another land bridge) between Siberia and Alaska between 20,000 and 15,000 years ago, perhaps following herds of animals they hunted. But during the ice age there were huge ice sheets that would have prevented humans from traveling beyond Alaska. Then between 15,000 and 12,000 years ago, as ice sheets retreated, a passage may have opened up for foragers to travel through, moving south through the Americas. Another hypothesis is that humans may have bypassed the ice sheets by slowly rafting down the Pacific Coast. Or it may have been a mixture of the two. Either way, Homo sapiens became the first and only species of our genus to inhabit the Americas.

Old-Fashioned Wiring

Humans were extremely well attuned to life as foragers, having existed in that state for 315,000 years and having evolved from previous hominines that also foraged for their existence. But we had to cope with potentially damaging situations that would end our genetic line there and then. Our instincts evolved accordingly.

In many ways, human instincts are designed to exist in small foraging communities. For example, take social anxiety. In modernity, there isn’t really any good reason to have anxiety prior to giving a talk to a crowd of strangers or being nervous before a first date. There are millions of people out there in your city. You can humiliate yourself in front of hundreds of audience members or potential mates, and still go out the next day and try again with a different group.

This was not the case for foragers in the Paleolithic. A group of humans might be a few dozen in number, and you would spend your entire life with them. If you made a fool of yourself in front of a large crowd of people, you might be socially ostracized, which would reduce your access to food and mates, or you might be thrown out of the group altogether if they disliked you enough. If you made a fool of yourself in front of a prospective mate, they might tell all the others, and your DNA would be rudely ejected from the gene pool forever. In fact, this sort of danger within a small, close-knit social hierarchy goes back at least as far as our last common ancestor with chimpanzees, 5 million years ago.

In that context, it makes sound evolutionary sense to have an instinct that agitates humans in social situations. Much of our instincts have evolved in a similar way. And many of them are ill-suited to modernity.

Foraging Life and Society

Foraging means hunting and gathering. By and large, due to sexual dimorphism (differences in average body size and strength), male humans hunted and female humans gathered. But we know from studying modern foraging groups over the past two centuries that there would have been overlap between the two groups. Some females possessed the athleticism and specialized knowledge to be hunters; some males possessed the required knowledge of plants to be gatherers and/or were too old or infirm to hunt. Further, an individual might have been personally predisposed to one activity or another, just as today different people prefer different jobs. But exceptions do not make the average, and generally women gathered and men hunted. This general pattern goes back at least 2 million years.

On average, 60 percent of food for foraging groups came from gathering. This was due to the feast-or-famine nature of hunting: You could go days without meat, then have a bonanza of several carcasses at once. Some social theorists have interpreted this percentage as indicating that females had equal “hard power” in foraging groups, if not full egalitarianism in both political power and roles. But this is contradicted by modern studies of foragers. It also ignores sexual dimorphism and the fact that men are exceedingly more violent both toward women and each other. In short, it is no good bringing in a bunch of nuts and berries if a man can bash your head in with a rock. Human power hierarchies were/are not based on production alone—if they were, the farming peasant class would have ruled in the Middle Ages—but instead, on coercion, tradition, and group loyalties.

But foraging societies also defy simple dichotomy. A low-ranking female was valued higher than a low-ranking male. If a female assaulted a male, there might be very little consequence; if a male simply insulted a female, he could be killed by other males in a foraging group. The only exceptions were the male leaders of a group, who could usually get away with more because of their rank. Power and rank mattered more than gender.

By and large, many foragers maintained monogamous relationships (particularly in ritualized marriages), but a few high-ranking men might practice polygyny (having more than one wife) due to their social status, and usually with religious justification. Beyond that, sexual and romantic relationships were just as turbulent and irrational in foraging communities as they are today. Emotionally, these humans were similar to modern ones, and thus probably experienced the same degree of emotions, from strong infatuations to tumultuous break-ups, jealousies, and infidelities, all of which likely contributed to interpersonal violence.

Violence was more common in the foraging world than in any subsequent period. Studies of Paleolithic skeletons that show signs of deliberately inflicted violence as a cause of death indicate a “murder rate” of approximately 10 percent. Most of these corpses were male. This is much higher than the murder rate in any modernized country—or any society in the last 5,000 years.

The typical foraging tribe went extinct every 200 years, on average—either due to genocide or through one cultural group of humans being conquered or absorbed by another group. A single human culture did not occupy a tract of land for thousands and thousands of years. Instead, for the majority of human history, biological or at the very least cultural genocide was the rule, not the exception.

When injury or sickness occurred, it was frequently a death sentence. And when foragers entered a region where food was scarce, they were at risk of starving. Simple things such as a broken bone, infected wound, or rotten tooth could kill you. Infant mortality was high, with 50 percent of children dying before the age of five. Furthermore, the fact that foragers had to be constantly on the move to find enough food for everyone meant that infanticide rates were quite high: around 25 percent.

On the upside, collecting food only took up part of a forager’s day. The average workday was 6.5 hours for foragers, compared to 9.5 hours on average for agrarian peoples, and the standard 8 hours for modern cubicle jockeys. The surplus time was used in socialization rituals of various kinds, including feasting by the campfire, dancing and the all-important politics of mating.

As a result of all the different sources of food, the diverse diets of humans (when times were good) actually left foragers quite healthy. The nomadic life also meant there was little opportunity for as many viruses and contagious diseases to grow, meaning foragers were much healthier than humans in the subsequent agrarian period. All told, one could reasonably make the argument that humans lived better in the foraging era than at any time prior to the days of developed countries in modernity.

By the time humans had spread across the world 12,000 years ago, we had multiplied into a population of 6 to 8 million people. While humans had already proven themselves a highly adaptive and powerful species, and the sophistication of their ideas and toolkits were unprecedented in the Homo genus, a great revolution was just around the corner. It would not only put humans on a course toward ancient and modern history but trigger a great acceleration in just 12,000 years—a blink of an eye in the timescales we have covered so far—and the acceleration has not stopped but only grown faster in modern times. It is worth bearing in mind that we stand on the precipice of further revolutions with potentially godlike and Universe-changing results. And it all started here, with a few million clever primates chipping tools out of stone.

chapter 8

The Dawn of Agriculture

Wherein humans grab more energy flows from the Sun via photosynthesis of crops • Crops support more people over a smaller land area • More potential innovators living at close quarters accelerate collective learning • Complexity goes absolutely nuts

After several tens of thousands of years of migration, humans had spread into every major world zone on Earth. Following the end of the last ice age, the world’s foraging population reached its zenith at approximately 6 to 8 million people. The largest population was in Afro-Eurasia, with an estimated 5 million people, followed by the Americas, with an estimated 2 million people, and Australasia, with 500,000 to 1 million people. Humans had yet to settle in much of the Pacific Islands until between 4,000 and 800 years ago.

Due to the end of the last ice age 12,000 years ago, the Fertile Crescent in the Middle East experienced a greening and abundance of food so that generations of foragers did not have to migrate in order to find it. Such territories are called “gardens of Eden” by historians and archaeologists. Foragers switched to semisedentary lives collecting surrounding vegetation and hunting animals, while reducing the amount of distance they traveled over the course of a generation.

Then, as populations boomed and food became scarcer, these foragers were forced into what archaeologists call the trap of sedentism and were compelled to domesticate plants and animals in order to prevent themselves from starving. This was the start of farming, where deliberate cultivation of food resources supported larger populations and a greater population density. The practice of agriculture spread into Egypt (or was independently conceived there), across the Middle East and gradually into Europe.

In China, similar “gardens of Eden” emerged roughly 9,500 or 10,000 years ago in the valleys of the Yellow River in the north and the Yangtze River in the south. The end result was also similar, with the inhabitants of East Asia beginning to cultivate plants and animals in order to support larger population numbers. Correspondingly, agriculture spread into Indochina and Japan. With agriculture now in the Middle East and East Asia, a combination of these practices gradually converged and met in South Asia—and the Indus Valley in particular.

The barriers of the Sahara Desert and the world’s oceans prevented the practice from spreading into certain regions of the globe. In West Africa, a similar “trap of sedentism” happened independently in the river valleys of the Niger and the Benue around 5,000 years ago, subsequently spreading across West Africa. This region has the highest population densities in Africa to this day. Millennia later, the practice of agriculture was taken toward the southern tip of Africa, with mixed results, where many Africans insisted on maintaining traditional nomadic lifestyles right up to modernity.

Meanwhile, the trap of sedentism occurred in Mesoamerica 5,000 years ago, and gradually spread south into Peru and north into the Pueblo societies of the southwest United States. Most intriguingly, an independent invention of agriculture also occurred in New Guinea 5,000 years ago, with populations remaining quite small. In Australia, foraging remained the primary mode of life, with the notable exception of “fire stick farming” (the practice of burning down large tracts of forest to clear paths, kill wildlife, and encourage fertility and rejuvenation), which was quite productive, and also instances of aquaculture in South Australia that sustained a few sedentary populations of several thousand people.

The Astonishing Complexity of Merely Planting a Seed

By several different metrics, the beginning of agriculture marks a new threshold of complexity in our story. For starters, the amount of energy flows humanity could capture to sustain their own complexity more than doubled, from about 40,000 erg/g/s in a foraging community with controlled use of fire to an average of 100,000 erg/g/s for the average premodern farming community. Bear in mind that the Sun itself scores only 2 erg/g/s in energy flows, single-celled life 900 erg/g/s, and most multicelled life achieves between 5,000 and 20,000 erg/g/s, depending on what it is doing. Structurally, an agrarian society is not just a network of cells in a single organism, but a fragile web composed of many different organisms: humans, plants, and animals. And the societal web was one of the most structurally intricate and densest in energy flows in the entire Universe. If our history had stopped in the Neolithic 10,000 years ago, this would still be a notable milestone in the history of the Universe.

In short, on one tiny rock in our solar system, couched within one tiny pinprick of unequally distributed energy that emerged shortly after the Big Bang, that little dot of energy was progressively growing in intensity, becoming denser and denser, more complex than anything in the vast cosmos around it.

Both foragers and farmers capture the overwhelming majority of those energy flows from the Sun, as do most organisms on Earth. Foragers will wander across a region and pick vegetation (which gets its energy from photosynthesis) and kill animals (which also eat those plants) and cook plants and animals by burning wood (from trees that also drew on the Sun).

But farmers would not rely merely on what grew naturally in the uncultivated wilderness. Some of those things were not fit for human consumption but took up valuable space. So farmers cleared forests, nurtured soil, irrigated fields, and planted rows and rows of high-energy consumable plants, with which they fed themselves and herds of hundreds of domesticated animals, which the humans used for their wool, milk, and meat instead of picking off a few wild animals in hunting parties. Humans started selectively breeding both plants and animals to become even more energy-efficient: fatter animals for meat or grain plants with higher yields.

This marks a shift in nature where a species is no longer adapting to the environment but adapting the environment to them. Ultimately, this new way of life supported more people. Agriculture drastically increased the amount of people the land could support—by 1,000 to 10,000 percent per square mile relative to the foraging era. Suddenly the carrying capacity of the entire surface of the Earth wasn’t 8 million foragers, but 80 million—and eventually 800 million—farmers.

The impact of increased energy flows and ultimately more people had a positive feedback loop on collective learning. With agriculture, there were more people (potential innovators), who increased the probability that a few of them in each generation would come up with innovations. Some of these innovations raised the carrying capacity of the population still further, whether through a new mode of farming, a new crop, or a new tool or technology. As a result, there were more people, which led to more innovation, which kept the process accelerating.

Not only did innovations speed up in agrarian societies compared to foraging ones, but farming regions quickly became the most populous regions on Earth. Instead of dwelling in nomadic groups of a few dozen people, humans began to live on farms with populations that large and congregating in villages that had hundreds of people. Foragers not only found it difficult to keep pace with the technological evolution of agrarian societies, but quickly found themselves outnumbered as well, as the land they had freely used to hunt and gather was gradually whittled away by sedentary farms. This forced many of them to move farther away or take up farming themselves. As a result, foragers starved or enacted raids and violence on farming communities (with the danger of retaliation). For the next 12,000 years, wherever agrarian societies appeared, this tragedy played itself out on the borderlands with foragers.

Booze, Diseases, and Excrement

From approximately 12,000 to 5,000 years ago, agrarian society (where it existed) was composed of farms and villages only. No cities, no states, no armies, no writing, no royal dynasties. None of the trappings of conventional history. A world of farms and villages prevailed for 7,000 years. For such a long stretch of time, increasing numbers of humans tried their hand at farming, with all the maladies that accompany it. This era before states is referred to as the Early Agrarian Era.

The Early Agrarian Era is generally characterized by a poor standard of living compared to the Paleolithic or the Era of Agrarian States (though the latter certainly varies by circumstances). For the entirety of the Early Agrarian Era, farmers used stone tools. And while the implements were inventive and testament to the power of collective learning, they weren’t very efficient. Nor did early farmers have very good fertilizers or irrigation.

As a result, the carrying capacities of the Early Agrarian Era were generally low. This meant that after the initial burst of plenty the first farmers may have enjoyed, there were numerous periods of overpopulation, malnutrition, starvation, and famine. Animal power was not adequately harnessed (no pun intended) in this period, so most of the planting and tilling was conducted by humans with the aforementioned primitive stone tools. It was down to adult and child labor (another advantage of having more kids compared to foraging) to cut down forests with stone axes, break open rough soils with stone hoes, and cut down the crops for harvest with hand-held scythes made of stone or bone.

Nor were the fertilizing benefits of animal poo fully realized at the time, meaning that soil would rapidly lose nutrients and render cropland useless for several years. Early agriculture was highly dependent on natural water sources (rivers), since there was neither the technology nor the manpower to conduct sophisticated irrigating techniques to make wider stretches of land suitable for growing crops, meaning the amount of land that could be effectively farmed was limited.

Even without famine, the conditions of the Early Agrarian Era were fairly disgusting compared to the Paleolithic. Foragers had a reasonably diverse diet, there is every indication that in normal circumstances they cleaned themselves regularly, and because they lived constantly on the move in small communities without domestic animals, there were few communicable diseases. In the Early Agrarian Era, on the other hand, humans were sedentary and remained within the same few square miles for their entire lives. This meant that the waste from their food products (rotten vegetables, carrion, and the offal of dead animals) and the improperly disposed of results of digestion (human and animal excrement) stuck around, often close to the home, creating unsanitary conditions from which people could fall ill. As a result, typhus and cholera became huge problems and were quite deadly and contagious. Typhus was caused by a virulent bacterium that could be transferred from person to person via mutual contact with food and could also spread through a water source. Once infected, a person was highly contagious and suffered from fatigue, swelling, pain, fever, delirium, hallucinations, heart problems, ulcers, and intestinal bleeding. Cholera is caused by a bacterium that infests the lower intestine and causes extreme bouts of diarrhea and vomiting, so dehydrating the victim that the skin retracts, the eyes sink, the skin turns blue and the person eventually dies. Other viruses and poxes were whipped up in larger populations living in close contact with each other and with their animals. These spread by coughing and sneezing, and the resulting poxes disfigured the skin, and caused swelling in the brain, seizures, fevers and death.

It did not help that humans frequently bathed and defecated in their own water supplies, as did their neighbors and many of their domesticated animals. Bathing did not necessarily get one clean and one could fall ill from it, so in some regions personal hygiene fell of fashion, with regular bathing actually being considered unhealthy (in other areas, groups still bathed regularly by custom). Lack of bathing further exacerbated health problems. And there were no reliable soaps or antibacterial agents for thousands of years. People became accustomed to body odor and (as a result of diet and lack of dental hygiene) bad breath and rotten teeth.

There was also the problem of contaminated drinking water from these same causes, which made drinking water alone quite unhealthy. The happy result of this (or unhappy result, depending on your perspective) was the invention of alcohol. Via fermentation, watered-down meads, beers, and wines were made safer to drink than pure water. That is not to say that humanity spent the next several thousand years of history drunk off their heads (though that would be an amusing explanation for some decisions): Most beverages were not as potent as the ones that began to be distilled, commercialized, and sold for recreational drug use purposes in the nineteenth and twentieth centuries. The average alcohol content of premodern beer was around 2 percent. But the specter of alcoholism in 10–25 percent of the population actually goes further back than the start of human farming. It goes back 66 million years when our shrew-like ancestors would eat rotting fruits and wild grains, and consume very small amounts of fermented alcohol as a result, getting a small reward of dopamine in their tiny brains. The pleasure response was evolved to encourage this behavior, prompting our ancestors to consume rotting stuff in order to stave off starvation and increase our chances of survival. Once we started mass-producing alcohol, we essentially glutted ourselves and this neurological response went into overdrive.

Early farmers also lived at close quarters with domesticated animals, sometimes even within the same dwelling, and the transference of viruses and bacteria between humans and their domesticated animals bred avian and swine flu that could rapidly sweep through and ravage a human population. Food and waste products also attracted pestilence. Rats, fleas, and cockroaches became commonplace. The regular denizens of filth kindly shared a new range of diseases, including various forms of infection, dysentery, and dreaded variants of the plague.

Sound appealing? If at any point in our story thus far you thought “complexity” was synonymous with “progress,” then let the Early Agrarian Era disabuse you of that notion.

It Takes a Village . . .

Putting the famines, pestilence, and diseases that could make you shit yourself to death aside, these early farming societies were able to support way more people per square mile than the foraging cultures from which they emerged. The result was an acceleration of collective learning and a resulting rise of complexity.

In the foraging era, the center of gravity for a society was the family. Kinship was the primary mode of maintaining governance, and alliances between groups were maintained by ritualized intermarriage. The rise of agriculture added another layer to this societal complexity. The farm still consisted of the family, with each member engaged in daily duties for subsistence, and with intermarriage occurring between families on neighboring farms. But the social life of the agrarian society converged in the village, a place populated by a few hundred people who would gather to exchange things (agricultural goods, tools, and information) and engage in the governance of affairs that affected the wider community (crop yields, problems arising from the weather, the possible threat of raiders, and the resolution of disputes between families). Villages were also places where grains could be stockpiled in case the wider community was struck by famine. There even appears to have been the development of religion in the Early Agrarian Era, with villages partaking in increasingly elaborate burial traditions for their dead. These burials yield an array of jewelry and other decorative items, which may well have denoted status, and thus the increasing sophistication of hierarchies.

In terms of violence, the majority of it doubtless remained interpersonal, as in the foraging era. But with sedentism and the introduction of land claims, crop yields, and possession of livestock came conflict over property. This may have manifested itself in either thievery by neighbors or land disputes between them that were arbitrated by the wider community.

There was also the new problem of raiders: neighboring cultures (either other sedentary farmers or non-sedentary foragers) who would rampage across a farming region, taking crops, livestock and tools, and perhaps even kidnapping women and children. The earliest agrarian settlements, such as the village at Abu Hureya in Mesopotamia, which housed sedentary farmers 10,000 years ago (8000 bce), don’t show much sign of defensive apparatuses. But as the agrarian era dragged on, farming communities begin to build walls, ditches, and watchtowers around local villages. One of the most impressive examples of this is the village of Banpo in China, which lasted from 7,000 to 5,000 years ago (5000 to 3000 bce), and where all the dwellings were clustered in a group behind a wall which was surrounded by a ditch.

Excavation in Banpo Neolithic Village in Xi’an, China

An even older example is the settlement of Jericho in the Fertile Crescent, which was converted into a farming village 11,500 years ago. The original settlement had no structural defenses but had a cluster of houses built upon a freshwater spring that was directed via primitive irrigation ditches toward the surrounding 6 square miles (10 sq km) of farmland. By 10,000 years ago, however, a wall was erected around the village.

The purpose in both of these cases seems clear. In a village where trade was conducted between farmers, where some grains may have been stockpiled, and thus there would occasionally have been a cluster of resources, defenses were required in order to prevent large raiding parties from coming along and “redistributing” the community’s wealth. Please note, however, that these defensive structures in a village do not necessarily denote the existence of large-scale warfare—that was beyond the resources of Early Agrarian societies. Instead, these raiding parties were opportunistic, skirmishing with defensive militias formed by local farmers on the frontier.

Power and Hierarchy

In order to organize this extra layer of society and cope with the many legal and defensive needs of a denser agrarian community, we see the microcosm of entrenched hierarchy, which is any hierarchy established on more than personal rule: that is, with a ruling class who you have probably never met. Bear in mind that during the Early Agrarian Era, the overwhelming majority of the population were engaged in subsistence farming to stay alive. A very small minority of people took on positions of authority to arbitrate disputes and organize infrastructure projects that could not be executed by a single individual or family.

The appointment of such authorities within a farming community would have come about in one of two ways (or both). The first, and most likely the earliest, was “bottom-up power.” When we discuss power, we are talking about an individual or council of people possessing the authority to issue commands and have reasonable expectation that those commands would be carried out. If you want to translate this into more universal terms, it is the direction of energy flows in the form of food or human effort toward a certain goal laid out by an individual in authority.

In the “bottom-up” scenario, the farming community would appoint an experienced or sensible individual, usually an elder or council of elders (in Latin, maiores, from which we get the term “mayor”) to arbitrate disputes and make decisions for the community. These decisions would have bearing on the entire community (the system of energy flows). And in order to afford the time to make these decisions and shoulder these duties, the elders might be given food they did not farm themselves, so they would spend less time on subsistence living. At first, these positions were appointed on basis of merit, and decisions were obeyed by the community without a great deal of coercion beyond the interpersonal and the social browbeating of an individual or minority faction that did not want to play ball.

In this sense, the hierarchies of Early Agrarian societies were not much different from foraging ones, or even most primate ones. All primates have a dominance hierarchy of some sort. The difference is that once an agrarian population extended into the hundreds or thousands, it was difficult for an elder or group of elders to maintain dominance merely by being the strongest or by maintaining the strongest interpersonal alliances. There are only so many people within an agrarian community with whom the reigning authority could form a personal relationship. Instead, a power structure might involve formalized procedures of bestowing power, by vote, by inheritance, or by religious ritual. And in order for the commands of such an authority to be obeyed, the elder might quickly require a voluntary or paid group of enforcers.

Which brings us to the second method of establishing power, the “top-down” method. This is where consent from a community is not necessary, because the authority of an individual or council is backed by the threat of violence. By the time agrarian settlements began constructing defenses, there would have been a militia or group of men capable of violence in numbers. These groups would be used not just against outsiders but also against members of the community who did not obey commands or accept the judgment of arbitration in a community dispute. These enforcers needed extra energy flows as payment for their efforts, so they too did not have to spend their entire time farming. In order to maintain this cycle of energy flows, the elder could always use the enforcers to collect further tribute from the surrounding population. All this would have happened gradually, with the veneer of legality and consent within the village.

Please also bear in mind that Early Agrarian societies did not have the long history of ideological conditioning that predisposes us toward democracy. For instance, inheritance of authority might have seemed to them the much more natural course of action. The transition from a bottom-up, democratic (or at the very least meritocratic) appointment of a reigning authority to a hereditary, entrenched, aristocratic hierarchy could actually happen quite quickly.

This is not such a departure from our instinctual primate past, where chimpanzees maintain alliances based on inheritance, with the offspring of high-ranking members inheriting the alliances and protection once afforded to their parents. As such, the time elapsed between “bottom-up” and “top-down” approach may not have been equally distributed, though the exact timing of the development of leadership traditions (democratic, meritocratic, and hereditary) differed by region and culture.

Approaching “Conventional” History

As unpleasantly familiar as all these power machinations may appear to be, we must remember that most humans in this era lived in small, close-knit farming communities with fairly well-adapted values. Including close families and friendly neighbors. Just as small foraging communities by and large were stable and livable for many of the humans living in them.

Just as your own communities today have the ingredients to produce healthy, happy lives despite the thunder and disgrace of wider politics. Life in any period, really, is what you make it. The commonalities that unite all periods of human life were already in place at this point, because we have functionally been the same human animal across the millennia for over 315,000 years. The most notable aspect of the period of “conventional” history of the past 5,000 years is how rapid and “unconventional” the pace of change has been during it, and how pronounced the rise of complexity would be from here on.

chapter 9

Agrarian States

Wherein the first agrarian states arise • The world population grows dramatically • Cycles of rise and decline blight human history • Trade between states enhances collective learning • The evolution of printing sends knowledge sharing into overdrive, circulating among larger segments of the population

We are now starting conventional history. Nine chapters in. More startlingly, we will be covering the majority of conventional history (the first 6,000 years) in one chapter. It’s possible to do this by following the broad overarching patterns of complexity and collective learning. These patterns serve as a kind of “universal acid” for the jumble of names, dates, and events that form the totality of human affairs. Just like Darwinian evolution helps us make sense of the grim slaughter of billions of species in the fossil record.

Agrarian states still harnessed unprecedented power from the Sun for their crops and livestock, with 80 to 90 percent of people remaining farmers. But collective learning gradually made agriculture more efficient, leading to the spread of farming across the Earth and the appearance of something new: cities, bureaucracies, armies, artisans, scribes, and rulers who did not engage in farming. The next level in structural complexity. Collective learning caused the world’s population to increase, but it did not keep pace with agrarian birth rates, leading to recurrent population crises which kicked off worsening civil violence and even the fall of empires. These population cycles which influenced political events are known as “secular cycles.” Those trends form the deeper tides that propelled much of the “swirling foam” atop the waves of conventional history.

17th-century map of Babylon and Nineveh

Rise of the City

By 5,500 years ago (3500 bce), the world population had grown from 8 million foragers at the invention of agriculture to 50 million people. That was a lot more potential innovators for collective learning, and the pace accelerated accordingly. The transition from the Early Agrarian Era to the Era of Agrarian States (starting 5,500 years ago) is defined by:

1. the appearance of large cities with a division of labor (non-farmers being supported by surplus food crops)

2. the appearance of writing

3. the beginning of secular cycles (driving the rise and fall of empires).

In order to support a city, where many of the inhabitants are not engaged in farming, you need to grow surplus food in the countryside. Collective learning got to work in the Fertile Crescent around 7,000 years ago. Hardier tools made of soft metal slowly replaced those of wood, stone, and bone. Higher-yield crops were selectively bred by farmers over thousands of years. Irrigation introduced water to soils that were normally dry, unlocking previously untapped nutrients for plants. Using animals to plough fields cut up the soil much faster than any human could. Combined with favorable climates in the region 6,000 years ago, farming productivity exploded by leaps and bounds. This surplus food allowed villages and towns to grow larger and larger.

In Sumer, the town of Eridu grew from a farming village to a city of 10,000 people by 5,500 years ago (3500 bce). Between 5,500 and 5,200 years ago, a number of cities that size sprang up. But these were not as large as Uruk, to the northwest of Eridu. Fifteen times larger in land area, Uruk had up to 80,000 residents. This was a permanent human settlement on a scale never seen before.

With growing collective learning came more crops, which supported increased societal complexity. Uruk had a very pronounced division of labor, where non-farmers were fed by an increasingly efficient agrarian surplus. The city was ruled by a caste of priests headed by a priest-king. Under them were scribes who handled the complex logistics of the city. Palaces and temples were built by a large artisanal and labor force numbering in the thousands. Soldiers maintained law and order and manned the city walls. The city had a burgeoning linen and wool industry, many wealthy merchants, and enslaved people who were coerced to perform work as household servants or laborers. Outside the city, farmers would have constituted roughly 90 percent of the population and the priests owned 30 to 65 percent of the land. A good portion of farmers, too, would have been enslaved.

Slavery appeared almost immediately with large human settlements. If there were enough crops to support a ruling class, and enough crops to feed soldiers to protect them, there were enough troops to coerce people to do work against their will. Often there were pretexts to legitimize slavery: Someone got into debt, or was a criminal whose crimes were not heinous enough for execution, or was of a foreign religion or ethnicity. But in the majority of cases, the enslaved were enemy captives from a war. For over 5,000 years, until just a few centuries ago, slavery was the rule for all agrarian states and abolition was the very rare exception.

Warfare began. Sumerian cities needed farmland to feed their populations and keep them wealthy. Armies of thousands of troops began to form for the first time in human history. Uruk dominated in the period 5,500 to 5,000 years ago. Thereafter, increased competition from other city-states led to horrific violence. Uruk was conquered and sacked by its rival city Ur 4,550 years ago (2550 bce). There had always been violence in primate dominance hierarchies, even in human foraging ones, but now the bloodshed occurred on the scale of thousands of dead or enslaved people, with no sign that the cycle would ever stop repeating itself.

Rise of Writing

Uruk has the honor of providing us with the oldest surviving writing, inscribed by sticks into clay tablets dated to 5,500 years ago (3500 bce). These writings discussed agricultural produce and livestock. From 5,500 to 4,500 years ago, Sumerian writing evolved from the pictographic (where symbols had no relation to how the word was spoken in Sumerian) to a wealth of syllabic symbols for complex songs, poems, and histories, along with the addition of a system of numbers. Writing patterns would undergo similar evolutions in other agrarian states as they arose and evolved across the world.

In terms of collective learning, the advantages of written records are fairly self-evident. Instead of passing on all knowledge by oral tradition—where if there is a generation with whom it is not shared, it disappears—written records can slumber in an archive for centuries, only to be rediscovered. One can also communicate more complex and abstract information than if it were transmitted orally. This would include details of a history, but also calculations made in mathematics. All told, the written record made it less likely that the knowledge would be forgotten, as frequently happened in the foraging era. The only limitation to collective learning at the time was that very few people beyond scribes and priests would have been literate. Most parents and children, and most masters and apprentices, would have continued to pass on information by speech and physical demonstration.

Rise and Fall of Empires

The city-state of Akkad arose somewhere to the north of Sumer roughly 4,300 years ago (2300 bce). Its ruler, Sargon, conquered all of Sumer, all of Mesopotamia, pushed into the Levant, landed in Crete, and got as far north as Anatolia, as far east as Elam and as far south as the tip of the Arabian Peninsula. Multiple cultures were incorporated into the Akkadian Empire, and in some cases the Akkadian language was imposed on subjugated peoples. But even this empire lasted until only around 4,150 years ago (2150 bce), when it collapsed.

This would not be the last time such a thing would occur.

This is a phenomenon known as a secular cycle, which drives the rise and fall of empires. Around 4,200 years ago (2200 bce), droughts, an exhaustion of the soil from overuse, and the increased levels of salt in the soil from shortsighted irrigation techniques seems to have significantly reduced the carrying capacity. This appears to have kicked off a population crisis, where famines were more frequent, uprisings by various cities and aristocrats became more common, and the Akkadian Empire’s control over Mesopotamia weakened as the empire shrank. Eventually the empire was destroyed by Gutian “barbarian” invasions.

Ultimately, there is a relationship between collective learning, carrying capacity and the sociopolitical stability of an empire. The key to this is that despite the fact that collective learning was gradually increasing the carrying capacity—so that the world population increased from 50 million people 5,500 years ago (3500 bce) to 954 million people 200 years ago (1800 ce)—population levels frequently outstripped the carrying capacity.

Agrarian people had so many babies that their innovations in agriculture simply could not keep pace. So, instead, there were cycles of rise and decline every few centuries that had a profound impact on micro-historical events.

The pattern was as follows.

• Expansion: When the population is still low and expanding, things are prosperous for the average person because there is more land, more food, and higher wages, the ruling family has fairly good control over the aristocracy, and the empire is generally stable and able to expand its territory.

• Strain: As the population approaches the carrying capacity, the average person pays more for basic essentials and gets paid less for their work (if they get paid at all), rents go up, peasants sell off their land because it no longer supports them, and land and wealth coalesce in the hands of the very wealthy and they multiply in number.

• Crisis: When famine or disease or some other disaster reduces the population, the wealthy lose their peasants, their taxpayers, and the source of wealth from rents and payments for agricultural produce.

• Depression: The wealthy begin competing with each other in tremendous civil wars and uprisings, and also competing with the government, until 1) an invading army takes over, 2) the population of the elite is reduced to the point that peace and stability reign again for another population recovery, or 3) the empire collapses completely and the region becomes depopulated.

Collective learning gradually raises the carrying capacity, but this does not keep pace with population growth, so a kingdom or empire is thrown into these cycles of rise and fall every few centuries. This is how some of the big trends we’ve been observing have an influence on small-scale historical events.

It is also how humans differ from other species in nature. Usually when a species hits the carrying capacity of its ecosystem, the population crashes and then quickly recovers when the small number of survivors enjoy more food. But in the human case, there is an extra layer of complexity where large-scale violence and civil war can hold a population low for decades after the population crash.

Across the ancient world, we see this pattern playing out—in Mesopotamia, in the Egyptian Old, Middle, and New Kingdoms, and in China with the Xia, Shang, and Zhou dynasties. The collapse of each is led by a period of population strain, disease, and civil infighting, and is often finished off by foreign invasion and occasionally by a brief “dark age” where history grows quiet.

Almost every civil war, state collapse and era of prosperity and imperial expansion has some connection to this pattern from 3000 bce to 1800 ce (and longer, where agrarian states did not quickly industrialize).

phase

population

real wage

elite numbers

violence level

Expansion

Growing

High, with good standards of living for common people

Low/Moderate

Low, with large amount of state stability

Strain

Slowing

Shrinking, with declining standards of living for common people

Increasing

Rising, with mostly popular rebellions without much elite support

Crisis

Dropping

Increasing, with declining standards of living for common people who survive

Top-heavy societal hierarchy, lower orders begin to be impoverished

Substantially increasing with elite factionalism, competition, discontent

Depression

Kept low

Increasing, with standards of living eroded by violence and possible oppression

Gradually declining as socio-political strife continues

High, with elites competing with each other and weakening government for what resources there are left

Recovery (aka another expansion)

Growing

High, with good standards of living for common people

Low/Moderate

Low, with large amount of state stability

Complexity in Agrarian States

In terms of structural intricacy (the number and diversity of building blocks, networks, and connections in a system), agrarian states represent a huge leap forward in complexity. Instead of groups of a few dozen foragers, or early farming communities of a few hundred farmers, there were now cities of tens of thousands, with people doing a dramatic range of different jobs other than farming (a greater diversity of building blocks). These people were increasingly connected in states and empires composed of millions. Between these states, trade routes were growing stronger and more numerous.

In terms of energy flows, we can also see complexity increasing. As in Early Agrarian societies, most of the energy comes from the Sun. Plants absorb this energy via photosynthesis and these plants are then eaten by humans and animals (which humans also eat or from which humans harness their energy for labor). The food and wealth generated from farming goes to support non-farmers (artisans, scribes, soldiers, merchants, cooks, architects, kings, and so on) in the rest of the agrarian civilization.

At the highest level, at the government of the state, much of the energy flows from all this farming and economic activity is taken in the form of rents, tributes, and taxation. Currency itself is representative of the energy flows, because currency represents value, and can be used for goods and services. So in order to conduct the complex business of the state, governments harness a greater density of energy flow (average 100,000 erg/g/s) than has been seen before in foraging or early farming societies, or anything else in the Universe.

One can compare an agrarian state to an organism. The latter seeks out food (energy) to sustain or increase its complexity. In the same way, an agrarian state seeks land and wealth. Both organisms and states also compete for these resources. And if either runs out of energy flows, they die. The fossils of animals, the skeletons of humans, and the ruins of ancient civilizations all have that in common. They were something great but are no more. They are symbolic of the endgame of the Second Law of Thermodynamics.

Evolution of Agrarian States

Between 5,500 years ago (3500 bce) and 2,000 years ago (circa 1 ce), the world population grew from 50 million to 250 million people. Some 90 percent of them existed in Afro-Eurasia, 8 percent of them existed in the Americas, and 2 percent existed in Australasia and the Pacific. 5,500 years ago (3500 bce) the city-states of Mesopotamia and the kingdom of Egypt only controlled 0.2 percent of the Earth’s terrestrial surface. By the time East Asia, West Africa, and the Americas produced their first Agrarian States (the last of these rising in the Americas about 3,000 years ago), that percentage grew to 6 percent. By 1000 ce, the land area controlled by Agrarian States had increased to 13 percent. The vast majority of the Earth’s land was populated by stateless farmers or foragers, or was uninhabited by humans.

The world at this time can be divided into four zones: Afro-Eurasia, the Americas, Australasia, and the Pacific. These divisions are based on collective learning. No collective learning was passed between these world zones before the so-called Age of Explorations and their unification in one single web of collective learning. But there was information exchange between states and peoples within the Americas, Australasia, or the Pacific. These same goes for the continents of Africa, Europe, and Asia (though long-distance exchange could take several generations), which is why they are grouped into the Afro-Eurasian world zone.

Afro-Eurasia had the major advantage in collective learning. It had the largest populations—for instance, the large and sprawling Achaemenid Empire in 480 bce contained an estimated 50 million people, or 40 percent of the world population at the time. Agriculture had first arisen in Afro-Eurasia, as had agrarian states, so it makes sense that the largest clusters of populations existed in East Asia, India, the Mediterranean, and West Africa, rather than elsewhere in the world. It is here we see the rise and fall of the various Chinese dynastic empires; the Persian, Greek, and Roman empires; the origin and disappearance of the Indus River Valley civilization; and the gold-rich states of Mali.

The vast masses of millions of people in Afro-Eurasia prompted the evolution of diseases. Agrarian states were not any more sanitary than Early Agrarian societies (where people were sedentary, lived at close quarters with livestock, and drank contaminated water) and the larger populations allowed diseases more opportunity to evolve in deadlier and deadlier forms. Smallpox, bubonic plague, and a cocktail of other diseases swept across Afro-Eurasia multiple times in the Agrarian Era. This world zone acting as a petri dish for human contagion was to have a grim impact on the Americas, Australasia, and the Pacific with the unification of the world zones.

The Americas first adopted agriculture around 5,000 years ago (circa 3000 bce) and the first states emerged in Mesoamerica around 3,000 years ago (circa 1000 bce). There was a slight lag behind Afro-Eurasia in agriculture, which is why the American world zone had only 8 percent of the world population. Nevertheless, the cordon sanitaire of the Atlantic allowed the human experiment to run independently and much the same results occurred. In 500 ce, the city of Teotihuacan hosted a population of nearly 200,000 people, which is massive by any premodern standard. The agrarian states of the Olmecs, Mayans, Aztecs, and (farther south) Incas all carry the trappings of advanced civilizations.

The World Beyond Agrarian States

Large tracts of Northern Europe, the Sahara and Arabian deserts, and the plains of Central Asia remained stateless for many centuries—populated either by Early Agrarian societies or nomadic foragers. These hinterlands posed a major threat for agrarian states, should the states weaken during a crisis or depression phase of a secular cycle. It is not a coincidence that so many Chinese dynasties, for instance, were founded by “barbarian” invaders, or that the Germanic invasions supplanted the Roman Empire in Europe.

Central and South Africa, from the Sahara to the Cape, resisted agriculture and states for a much longer period. The delay in agriculture is because sub-Saharan Africa is one of the best environments for human foraging and one of the least forgiving for sedentary farming. Nevertheless, agriculture had spread into Central Africa by 1500 bce and managed to pierce deep into the Congo, with some cultures adopting agriculture by 500 bce. The practice of agriculture reached southern Africa by 300 ce. A few agrarian states began to appear in these regions just prior to the unification of the world zones circa 1500 ce.

North America saw Early Agrarian societies emerge by 600 ce, most notably the Pueblo societies of the southwestern US. The most impressive settlements that arguably could be called an agrarian state were in Chaco Canyon, which held 5,000 people and was built between 850 and 1150 ce. Beyond in the Great Plains, California, the eastern seaboard and Canada, semisedentary cultures mixed farming and foraging, while some exclusively foraged. But for the arrival of Europeans, agrarian states would probably have arisen in these regions as well.

In the Australasian world zone, the people escaped the trap of sedentism and the unsanitary conditions of agriculture completely. In terms of health, it was certainly far more preferable for people to forage, especially because Aboriginal practices were so productive. Aboriginal people used fire to burn down forests, kill game, and expose edible plants, and to clear paths for travel, while the fire-loving eucalyptus forests quickly recovered. The Australian continent was able to support somewhere between an impressive 500,000 and 1 million foragers.

19th-century reconstruction of Pueblo Bonito, one of the most extensive settlements in Chaco Canyon

The Pacific world zone was only inhabited by humans in the last 5,000 years, and some islands less than 2,000 years ago. New Zealand was only settled in 1280 ce due to the lack of sailing winds blowing down from the north. The populations in this world zone consisted of islands of a few hundred people through to larger island chains that contained thousands. For instance, the Hawaiian Islands supported up to 30,000 people, and there was a degree of domestication and irrigation there that arguably could be called agriculture.

The Silk Roads

There were many agrarian civilizations spread across Afro-Eurasia who could potentially share collective learning. But often these states were separated by vast distances, huge deserts or impenetrable forest, and travelers might be captured or killed on their arduous journeys. So for 3,000 years, transmission of collective learning was slow. The first trade route that crossed the entire Afro-Eurasian world zone did not exist until 50 bce. The Silk Roads allowed slow transmission of goods and information from China to India to Persia to the Mediterranean and, via the Saharan trade routes, to West Africa.

Despite the name, the Silk Roads did not just transmit silk, spices, or other commercial goods. They also transmitted religions, inventions, and mathematical ideas. For instance, Hindu numerals were invented in the 400s ce, were picked up by the Arabs during the Islamic invasions (hence the misnomer “Arabic numerals”), and made their way into Europe in the Middle Ages, replacing the clunkier system of Roman numerals.

Due to its large populations, many luxury goods and spices, China was the center of gravity for trade along the Silk Roads. Chinese goods were slowly transported piecemeal across Central Asia, often by nomads, and often taking more than one generation, but ultimately flooded into Middle Eastern and Mediterranean markets. In return, the West gave the East grapes, manufactured products, and horses. But the balance of trade lay with the larger populations of Asia.

The land-based route of the Silk Roads was an agonizing journey from East Mediterranean ports across the grit of Mesopotamia and Persia, and over numerous mountain ranges and deserts into India and China. These Central Asian routes not only meant a harsh commute but engagement with numerous nomadic and imperial forces, who might kill or rob you. Otherwise, the sea route ran down the Red Sea to Aksum (which made a fortune, allowing its tiny population to become a mercantile superpower in the first millennium bce), on to one of the many ports of India and then onward to Indochina and South China. It was by these sea routes that Islam spread from India to Malaya and Indonesia.

Afro-Eurasia had a conduit through which collective learning could flow through hundreds of different agrarian states on a supercontinent which in 1000 ce was populated by roughly 300 million people. The overwhelming majority of trade was not carried out by one merchant from one end of the Silk Roads to another, and the transmission of trade goods and information could take years or even generations to travel across Afro-Eurasia. Nevertheless, the Silk Roads were kicking off a slow, creeping revolution. Contemporaries at the time would not have noticed this, but it would soon provoke massive changes in human history.

The Evolution of Printing

In the premodern world, the greatest limitation to written knowledge was its circulation. The vast amount of collective learning still occurred orally in the premodern period, with all the slowness and flaws that method produces. Literacy still remained in the hands of scribes, bureaucrats, philosophers, and the elite. Written works remained scarce and expensive. Printing would change all that.

Original Chinese printing was done with woodblocks, emerging at the end of the Han period in 220 ce. Each page had to be carved into the blocks, slowing efficiency. Woodblocks were extremely bulky and hard to store and transport, every new copy or variation being started from scratch. In 1045 ce, Bi Sheng invented movable type, where words were placed onto clay tablets which could be rearranged to create a new sequence of words and then be imprinted on the page. Numerous Chinese philosophical, scientific, and agricultural works were regularly produced. Some books had a circulation of thousands.

The Koreans in the 1200s ce invented a metal movable type. The advantages of metal movable type are that it is durable, smaller, and easier to rearrange, and ultimately produces books at a faster rate. The Koreans did not use a press of any kind. They laid thin paper over inked type and took the impression by rubbing it with a wooden spatula. This was painfully slow. Nevertheless, with woodblocks or metal movable type applied by spatulas, the impact of early printing in China and Korea was to reproduce more copies of written knowledge at a faster rate than could be done by hand, increasing the number of books in circulation and the array of knowledge that could reach any one person who was literate. It must be noted that in East Asia, slower woodblock printing remained the dominant form until the nineteenth century, setting a limit on the collective learning that could be derived from the wider circulation of works.

In Europe, Gutenberg’s printing press was invented around 1450 ce and combined metal movable type (imported via the Silk Roads from the East) with a wine press (one of alcohol’s many virtuous usages) for quick composition of new pages and then relatively fast imprinting upon paper. This revolutionized printing. In the 1460s, three men could make 200 copies of a book in 100 days with a Gutenberg-style printing press. The same number of copies would take three medieval scribes thirty years. During the sixth century ce, Benedictine monasteries made a rule of housing around fifty books. The largest library in the mid-fifteenth century West was that of the Vatican. It contained around 2,000 books. A private scholar of middling rank could easily acquire that many in the seventeenth or eighteenth century.

There were an estimated 8 million copies of books produced in the fifty years between 1450 and 1500 ce. This quite likely exceeds the entire number of books that were hand-copied in Europe since the year 500 ce. Between 1500 and 1600 ce, between 140 and 200 million books were printed. This proffered the Europeans a tremendous advantage in collective learning that aided the spread of the Renaissance and Reformation and would trigger the Scientific Revolution.

Greater profusion of information, greater connectivity, and a gradually rising rate of literacy meant that another explosion in complexity was just around the corner.

chapter 10

The Unification of the World

Wherein Afro-Eurasians stray into other world zones • China nearly launches the Industrial Revolution • An Afro-Eurasian disease in a long line of diseases kills millions • The Turks inadvertently cause the next rise of complexity • Slavery continues • And the costs of complexity are made palpable by and for humanity

By 1200 ce the world population was approximately 400 million, but not without the dips and declines of secular cycles. For instance, in 1 ce the world population was roughly 250 million. But after the decline and collapse of the Roman Empire, Han China, and numerous other agrarian states, the world population had shrunk to 200 million by 600 ce. By 1200 ce, the world had recovered and massively surpassed its ancient maximum.

The land-based and seaborne Silk Roads had unified Afro-Eurasia into a fairly robust network of collective learning with shared ideas and innovations (and, horrifically, diseases). The other three world zones—the Americas, Australasia, and the Pacific—had not yet entered this network to spur on collective learning to be even faster. The unification of the world zones into a single web of collective learning would harness the innovative power of all humans on Earth and set humanity on a collision course for modernity, with all the higher complexity it has brought.

The Medieval Origins of Globalization

An agrarian state gained the overwhelming majority of its wealth (that is, energy flows) from agriculture. Landlords would have a share of the crops produced, or would collect rents, and central governments would collect taxes and tributes. But thanks to the Silk Roads, that was changing. Merchants were making more money and were becoming increasingly influential. The Italian merchant states of Venice, Genoa, and Florence had become the wealthiest in Europe despite their small size, the spice traders and Tamil kings of Ceylon and South India managed to achieve the same dynamic, and the bustling international spice trade brought increasing wealth and power to the Srivijaya kingdom in Indonesia. All were smaller states that wielded tremendous wealth simply by account of commerce, which in many ways outstripped states of a similar size that relied on tax income from the land.

In the eleventh century, the start of the Crusades brought Europe into closer contact with the Middle East. The Vikings made temporary forays into North America. In 1271 ce, Marco Polo traveled across Central Asia on a perilous journey to China, and when he published his account of these travels in 1300 ce, European society was shocked at the level of riches in East Asia, intensifying the motivation of European merchants to trade there.

And there was a very good reason to be motivated to trade in China. Equal interest did not exist along the Silk Roads. Europe and Africa were eager to access Asian markets in order to obtain what they could not produce themselves—silks, spices, pottery, and so on. The successive Muslim caliphates of the Middle East were still making quite a packet of cash playing middlemen for Chinese goods and Indian spices, since they dwelt along the only trade routes to the East (nobody had rounded the Cape of Africa yet). China, however, produced the most desirable goods and in large quantities and thus had a dominant position in the entire network of trade. Just as modern globalization has been driven by a wealthy and technologically advanced West, the medieval origins of globalization were driven by a wealthy and technologically advanced China.

The First Great Divergence

Long before the West raced ahead of the rest of the world economically and technologically in the nineteenth century, China had done the same centuries earlier, to the point that it could have had an industrial revolution. This was entirely down to collective learning, driven by the number of potential innovators, people who could come up with a new innovation in their lifetimes. The larger the population of humans, the more rolls one has at the dice every generation.

Between 500 and 1100 ce, with the spread of wet rice production in southern China, the carrying capacity absolutely exploded. Per hectare, traditional varieties of rice support around six people compared to three people on a hectare of wheat. This intensified in the Song dynasty (960–1276 ce). The Song government introduced a high-yield strain of rice from Vietnam. They appointed “master farmers” from local communities, and disseminated new farming techniques and knowledge of new tools, fertilizers, and irrigation methods. The Song also introduced tax breaks on newly reclaimed land and low-interest loans for farmers to invest in new agricultural equipment and crops. The Chinese government distributed 3,000 printed copies of Essentials of Agriculture and Sericulture to landowners in order to improve crop yields. Wet rice farming by this method produced two to three crops a year.

During the 900s and 1000s ce under the Song dynasty, the carrying capacity of China increased from 50 to 60 million to 110 to 120 million (nearly half the world’s population), with record high population densities, such as 5 million people farming an area of 37 by 50 miles (65 x 80 km). By 1100 ce, China constituted 30 to 40 percent of the population of the globe, compared to Europe, which constituted 10 to 12 percent.

Chinese collective learning advanced by leaps and bounds. For instance, the annual minting and use of coin currency was increased greatly under the Song dynasty. They introduced paper currency. Farming techniques improved: use of manure became more frequent, new strains of seed were developed, hydraulic and irrigation techniques improved, and farms shifted to crop specialization. Coal was used to manufacture iron (the same iron process that fueled early British industrialization), and production increased from 21,000 tons per year under the Tang (618–907 ce) to 125,000 tons under the Song. The Song dynasty was the first to invent and harness the power of gunpowder. Textile production showed the first ever signs of mechanization.

Share of the world population c. 1100 ce

It is interesting to speculate what modern history would have looked like if the Industrial Revolution had happened in China. Certainly the sociopolitical history of the world would have looked decidedly different, with Chinese ships arriving off the coasts of America and Australia, perhaps with the intent of colonizing there (and inadvertently passing on deadly Afro-Eurasian diseases), and the Age of Imperialism happening at the expense, rather than to the profit, of Europe.

The Black Death and Secular Cycles

Thanks to collective learning, innovations in agriculture, and the opening up of new lands to farming, the world population ballooned from 300 million in 1100 to 400 million by 1200. The common population was fairly prosperous, with low rents and decent wages, ate meat semi-regularly, and were in fairly good health by premodern standards. Agrarian civilizations were fairly stable (internally at least), compared to the periods that came before and after.

But population growth began to outstrip agricultural innovation. Between 1200 and 1300, the population only grew to 432 million. Population strain was starting to set in. The standard of living for the agrarian peasantry declined: They ate less meat, their wages shrank, their rents rose, smallholding farmers had to sell their land, and elites set up huge estates as their numbers multiplied several times.

From 1315 to 1317, the Great Famine of Europe killed an estimated 15 percent of Europe’s population. A famine in China in (1333–37) carried off similar numbers. The common population declined and the elite incomes that depended on them were reduced, and some elites even became impoverished. Politics destabilized across the world, with an increased number of elite rebellions, assassinations, and palace coups.

But much worse was on the way, courtesy of the Silk Roads. The Black Death was an extremely deadly disease caused by the bacterium Yersinia pestis, carried by fleas, which in turn are carried by rats. Once bitten by an infected flea, a human develops swollen lymph nodes around the groin, which are painful to the touch. As the bacteria works its way through the human bloodstream, plague victims experience fever, weakness, delirium, headache, bloody vomiting, and the death of flesh and internal organs, which can turn black and gangrenous. Death usually occurs within a week to ten days, and death was the outcome for roughly 80 percent of bubonic plague victims. If the plague turned pneumonic, the death rates were between 90 and 95 percent; very often people with pneumonic plague died within just two to three hours of catching it.

The Silk Roads transported the Black Death east and west. Sporadic outbreaks occurred in China in the 1340s and a more severe pandemic swept across all of China between 1353 and 1354. The resulting population downturn, elite infighting, and state collapse led to the overthrow of the Yuan dynasty in favor of the Ming in 1368. Plague and a depression phase reduced the Chinese population from 120 to 140 million in 1200 to 65 million people by 1393.

The Black Death also spread to Persia from Central Asia by 1335, killing an estimated 30 to 50 percent of the population, including the ruler of the Ilkhanate, which had dominated the region since the fragmentation of the Mongol Empire in 1256–59. This caused the collapse of the khanate into several rival kingdoms. From 1338 to 1344, the Black Death spread across the trade routes of the Golden Horde to the north, killing an estimated 30 to 70 percent of the population.

In 1344, an already infected army of the Golden Horde besieged the Genovese-held Crimean trade port of Kaffa. The Golden Horde placed plague corpses onto catapults and flung the bodies over the city walls, in one of the first recorded instances of biological warfare in human history.

The Black Death managed to get on board Genovese trading ships and began to infect the Mediterranean. The disease arrived in the port of Constantinople in 1347 and then spread overland across Anatolia, reaching Damascus in 1348, where an estimated 2,000 people died per day. That same year the Black Death reached Egypt, where it killed an estimated 50 percent of the population of Cairo. Due to the Muslim tradition of making a pilgrimage to Mecca, the Black Death arrived in their holiest of cities in 1349.

Back in 1347, the Genovese traders had also traveled on to Greece, Sicily, Sardinia, Corsica, and Marseille. In 1348, traders reached England, Ireland, and northern France. In 1349, the Black Death rushed through southern Spain and got as far as Morocco. Infected ships arrived at Bergen in Norway. The plague spread from England to Scotland, from Norway to Sweden, and from France to the Holy Roman Empire in 1350. Poland and Russia were hit in 1351 and 1353. Only the small, cold-dwelling population of Finland was spared.

In 1300, the world population had been 432 million. By 1400, from a mixture of famine and plague and the decades of violent instability that usually follow depopulation, the world population had shrunk to 350 million people.

Plague doctor

An intriguing side-effect of population collapse, however, is that life becomes quite prosperous again for the common people. A shortage of labor means higher wages, an abundance of land left over by the dead means lower rents and sustainable peasant farms, while food is cheap because there are fewer people buying it. The peasantry might even possess what we would call a “disposable income” for a few modest luxuries. The common people of Afro-Eurasia had a high standard of living and a larger “real wage” than in any period prior to the Industrial Revolution.

The Age of Chinese Explorations

After the Black Death, the Ottoman Turks shut down much of the overland trade on the Silk Roads. The disruption of the network of exchange prompted explorers at either end of the Afro-Eurasian supercontinent to find new routes by sea.

In 1403, the Ming dynasty began construction of a gigantic fleet of warships and merchant vessels that dwarfed anything else in the world at the time. The Chinese exploration fleet was composed of 317 ships, some of them approximately 394 feet (120 m) high, with three or four decks, carrying a massive army of 28,000 men to, shall we say, add weight to trade negotiations.

Starting in 1405, numerous expeditions were launched. The Chinese fleet sailed around Southeast Asia and to India on several occasions. They sailed down and conducted trade in Indonesia. They made landfall in Arabia and East Africa on several occasions. In total, seven expeditions were made.

The final voyage ended and returned home in 1433. At this point China, already a mighty empire with many natural resources and luxury goods, turned to isolationism. If these voyages had continued, it is not unreasonable to speculate that the Chinese could have eventually sailed around the southern tip of Africa, perhaps even achieving direct trade with Europe. It is also possible the Chinese could have moved farther south from Indonesia to Australia. And perhaps the Chinese could even have navigated the Pacific, taking them to the Americas.

The Age of European Explorations

In the fifteenth century, European states could not gain as much income from taxing the farming population as they had prior to the Black Death, and so merchants and commercialism began to be looked upon more favorably. Yet the Ottoman Turks had shut down much of the trade via the Silk Roads in their bid to conquer Europe. The Europeans recoiled West.

By the 1420s, the Portuguese and Spanish had landed in the Canaries, Madeira, and the Azores, and charted a good distance down the seemingly unending African continent. In the 1440s and 1450s, Portugal began a great deal of trade with the Mali Empire. Portugal gained access to pepper, ivory, gold, and the African slave trade. Bartolomeu Dias reached the Cape of South Africa in 1488. And in 1498, Vasco da Gama rounded Africa and reached India, and brought back a cargo of spices. Bypassing the hostile Ottomans, da Gama was able to purchase his cargo for 5 percent what it would have cost him buying from eastern Mediterranean sources.

The problem with sailing around Africa is that near the equator one hits a region called the “doldrums.” This is a long stretch of ocean where the winds are frequently too weak to propel sail, and where ships were frequently hit with dangerous storms.

Alternatives were already being sought. In 1492, Ferdinand of Aragon and Isabella of Castile commissioned an expedition led by Genovese explorer Christopher Columbus (little did they know the voyage had already been made by the Vikings nearly 500 years earlier). Columbus left Castile in August, sailed west, and reached the Bahamas in October. He went on to visit Cuba and Hispaniola. Upon the native populations, Columbus established a regime of enforced slave labor, sexual slavery, and mutilation for disobedience; all the while the island populations were gradually wiped out by European diseases. To his dying day, Columbus was certain that he had landed in Asia.

Christopher Columbus’s soldiers chop the hands off of Arawak Indians who failed to meet the mining quota

In 1519, the Spanish monarchy commissioned Portuguese explorer Ferdinand Magellan to take five ships, sail south of the Americas and enter the Pacific, whereupon Magellan crossed the vast ocean and reached the Philippines, where he was killed in 1521. Only one ship managed to return to Spain, in 1522, under command of Juan Sebastian del Cano, being the first crew to circumnavigate the globe.

The sixteenth century set off an explosion of European and colonial merchant ventures to Asia and the Americas, with states, private investors, and individuals seeking vast fortunes. Habsburg Spain dominated these trade networks and the acquisition of colonies in some of the most mineral-rich parts of South and Central Americas. Other prominent nations that joined the colonial effort were England, France, and the Netherlands, with even a few attempts to set up colonies by Scotland. The nations of Central and Eastern Europe largely missed out on the Age of Explorations due to local wars and their geographic locations.

From 1519 to 1521, Hernán Cortés led a few hundred Spanish conquistadors, armed with gunpowder weapons and a cocktail of diseases against the Aztecs. As a result of the high death rates of Aztecs at the hands of European disease and Cortés allying with various local enemies of the Aztecs, all of Mexico fell into Spanish hands within a few short years. In 1532, Francisco Pizarro led a similar expedition against the Incan Empire, and was also aided by gunpowder weapons and the horrible ravages of European disease. However, the Incan Empire stretched across vast and difficult terrain and the Spanish did not fully conquer the empire until 1572, as the result of a long and grueling war of annihilation.

Painting of the Aztec capital Tenochtitlan-Tlatelolco on Lake Texcoco

The Slave Trade

In the Caribbean and South America, Europeans had stumbled across a climate that was ideal for sugar plantations. The question was finding enough labor to engage in such grueling work. Lower-class Europeans weren’t the answer. Only indentured servants shipped over to the Americas could possibly be forced into it. And they soon moved on after their contract was up, and there certainly weren’t the numbers of people willing to do it. The Spanish and Portuguese initially tried forcing the native inhabitants of the Americas to do it. But they knew the countryside and frequently escaped back to their people. Those who stayed often died of Afro-Eurasian diseases. So the Portuguese utilized the slave trade with African rulers they had entered into half a century earlier.

Slavery had existed since the inception of agrarian states 5,500 years ago. There had been slavery in Europe, in Africa, and in Asia. The Aztecs and the Incans had enslaved people. As had the Chinese, Koreans, and Indians. Of the roughly 55 billion people who lived in the Agrarian Era, an estimated 3 to 10 billion of them may have been enslaved.

Europeans were no strangers to slavery. The Romans had owned huge plantations across the Mediterranean world operated by millions of the enslaved. The Middle Ages blurred the lines between slavery and serfdom, which wasn’t much better (though it certainly was an improvement). In fact, serfdom was an early medieval perversion of older systems of slavery, even in its name: “serf” being derived from the Latin servus (slave). To the east, Russia did not abolish serfdom till 1861.

The kingdoms of West Africa had been engaging in the Muslim slave trade for several centuries by the fifteenth century, with the forced transport of people across the Sahara. The demand for enslaved Africans had increased since the number of Europeans captured and enslaved by Muslims had slowly declined since the eleventh century. The Africans themselves primarily derived their enslaved from peoples they conquered in war (but debt or birth into an enslaved kin-group were also causes for slavery), and Africans either kept them or sold them off across the Silk Roads. When the Portuguese opened up trading relations with African rulers in the 1440s, the slave trade was extended to them as well.

The horrors of transportation killed 10 to 20 percent of Africans moved across the Atlantic. The route-march east across the Sahara claimed 25 to 50 percent of those sold or captured. In total, 11 to 14 million Africans were taken west across the Atlantic in just 400 years, and 10 to 17 million Africans were taken east across the Sahara over 1,100 years. An average of 5 to 15 percent of the population were enslaved in the agrarian states of Africa.

Slavery was the rule of agrarian states. Absence of slavery was the exception. From the perspective of the chained, across the globe, it had been a hideous 5,000 years.

The Portuguese were responsible for 45 percent of all enslaved people taken during the Atlantic slave trade. Their former colony, Brazil, was the destination of 35 percent of all those enslaved in the Atlantic trade and also one of the last of these countries to abolish slavery, in 1888. The Spanish account, for roughly 15 percent of all enslaved Africans, transporting most of them to South America and their Caribbean island holdings. They also made more determined use of Native American slavery, particularly in their mining operations. The French transported 10 percent of enslaved Africans to their holdings in the Caribbean, mostly plantations. The Dutch did the same with 5 percent of the total number.

In the seventeenth and eighteenth century, forced plantation slave labor expanded from sugar to include the production of tobacco (another highly addictive product) and cotton for textiles. This made slave labor desirable for farms in the southern half of the Thirteen Colonies. As such, the British imported 15 percent of the total number of African enslaved Africans to their Caribbean plantations and approximately 10 percent were imported to lives of bondage in the future United States, for a total of 25 percent of the slave trade.

West African men, women, and children enchained and marched into slavery

In the 1500s, an estimated 400,000 to 500,000 Africans were enslaved by Europeans (1 percent of Africa’s population). In the 1600s, this number increased to 1 to 1.5 million (2.5 percent). In the 1700s, 5 to 8 million people (10 percent) were bought, bound, packed into appalling conditions in ships, and sent to the Americas.

It was the horrific scale of the 1700s that finally sparked the abolitionist movement in Great Britain. A thirty-year public and parliamentary campaign led to the British abolition of the slave trade in 1807, making further purchase and transportation illegal, with the United States’ ban taking effect at the start of the following year. And the British Navy became actively engaged in stopping the transportation of enslaved Africans by other nations. Nevertheless, the remaining slaver Atlantic states succeeded in transporting an additional 3 to 4 million people from Africa in the 1800s (4–5 percent of Africa’s population). The British Empire abolished slavery itself in 1833, and slowly, by brutal civil war in the United States and by gruesome revolution or peaceful legislation in other countries, the rest of the Atlantic nations followed suit in the subsequent decades.

In Africa itself, slavery continued, particularly in North Africa, where slavery was given a religious and ethnic justification. In the late nineteenth century, European imperialism and intervention attempted to expunge slavery from Africa itself, but very slowly and often ineffectively. Or, depending on the colonial power, even half-heartedly. Or prolonged it.

Even today, in the postcolonial era, slavery in Africa is still a problem. In modern Nigeria, there are 700,000; in Ethiopia, 650,000; in the Congo, 500,000; and in total roughly 5 to 10 million people leading lives as effectively enslaved in Africa. Beyond Africa, there are 12 to 14 million de facto enslaved people in India, 2 million in Pakistan, and 3 million in China. There are currently 47 million enslaved people worldwide, which is roughly the population of Spain.

Ecological Imperialism

Europeans brought to the Americas and Australasia all their domesticated farm animals, a necessary ingredient for settler colonies. Sheep and cattle were bred so prodigiously that they quickly became some of the most common mammals to be found in either world zone. In the Americas, by 1600 there were 20 million sheep and cattle.

When humans arrived in the Americas 12,000 years ago, they hunted American horse species to extinction. Once Europeans arrived, they reintroduced the horse. Some horses were obtained by Native Americans. As a result, the lifeways of Native Americans in the Great Plains were radically changed. Many cultures switched from agrarian cultures that had existed in the Great Plains for thousands of years to become nomadic foragers once again. Prior to the horse, Native Americans would camouflage themselves with pelts and crawl along the ground to get close enough to herds of buffalo. When they got near, they’d spear a buffalo before the herd started to stampede away. With the arrival of the horse, Native Americans could now keep pace with the buffalo and spear them as they chased them, or else herd them off the edge of cliffs. By the nineteenth century, the Great Plains peoples had kept horses as a keystone of their culture for 300 years. Long enough that some Native American accounts depict the horse as always being in the Americas and part of their way of life.

19th-century buffalo hide painting of a horse raid by Dakota artist Long Dog

New World crops in turn impacted Afro-Eurasia. In terms of caloric intake, maize bequeaths more than wheat and only falls short of rice per square mile. An example would be potatoes, which is not only quite good on the caloric front but actually enriches the soil with nutrients as they grow. Maize and potatoes also come with the advantage that they are easier to prepare and cook than something like wheat or rice. The Americas also gave the world tomatoes, yams, and squashes that were similarly high yield per square mile. The European carrying capacity, where American crops were adopted, increased by 20 to 30 percent. In China, the population was starting to experience mass famines in the 1630s, but adoption of American crops prevented another mass famine from happening until the nineteenth century, during which time the Chinese population increased from 150 to 330 million people.

Illustration of the “Three Sisters,” a mutually beneficial New World planting arrangement of corn, beans, and squash

Disease utterly destroyed the inhabitants of the Americas and Australasia. For thousands of years, at this point, Afro-Eurasia had been host to 90 percent of the human population, most of whom were living in densely packed agrarian states where basic hygiene and germ theory were conspicuously absent. Inhabitants of Afro-Eurasia had developed genetic resistances to diseases over hundreds of generations, but the populations of the Americas and Australia had no such biological resistance. European colonists brought over smallpox, typhoid, cholera, measles, tuberculosis, whooping cough, and numerous influenzas. While these were still deadly to Europeans, the impact on indigenous populations with no resistance was much worse.

In the Americas, Afro-Eurasian diseases are estimated to have wiped out 90 percent of the population between 1500 and 1620. Some 50 million people were killed in a world populated by 500 to 580 million. Just by the simple act of Europeans showing up. And that was done in the space of a century. In 1620, only 5 million Native Americans remained in North and South America. This was an unsurpassed obliteration of human civilization the equal of which cannot be found in human history. Afro-Eurasian diseases would continue to wreak havoc on Native American populations throughout the nineteenth and into the twentieth century.

In Australia, the cocktail of Afro-Eurasian diseases reduced the Aboriginal Australian population by at least 73.75 percent between 1788 and 1900. Most scholars today agree on a precontact population of around 800,000. In 1850, the population had already shrunk to only 200,000 people. In 1900, the Aboriginal population was 90,000. Using Butlin’s calculations, that European expansion of farmland caused an upper limit of 100,000 Aboriginal Australians to starve to death, and using Reynolds’s estimate for the unrecorded number of Aboriginals who died in frontier violence against recorded European deaths, that makes 73.75 percent of the population reduction being from disease, 12.5 percent from starvation, and 2.5 percent from frontier violence in a little over a century.

Populations, by continent, 1500–1900

Imagine if, in the space of a century, 8 billion people on Earth started dying until there was only 800 million left. Cut down the population number of your own nation to 10 percent if that strikes closer to home. That was the cost of the unification of the world zones. While American crops were raising the carrying capacities of Europe and Asia, sending their populations soaring, the populations of the Americas and Australasia were being reduced at nightmarish rates. Even writing this now, I can barely conceive of the devastation and suffering wrought by such biological terror.

On the Verge of the Anthropocene

Reflect back on the journey of complexity thus far. The firestorms of the Big Bang and exploding stars. The hellish formation of the Earth. The blood-soaked evolution of species. The propensity of primates for murder. The deprivations and disease of the Agrarian Era. And now this. Complexity is not synonymous with “progress.” All of our comforts and conveniences today have come at a tremendous cost that most people can barely contemplate.

Complexity exists in a Universe beset on all sides by the Second Law of Thermodynamics. With every threshold of complexity has come destruction and, where there is consciousness, suffering. Nothing about our current point in history was predestined. It has not been a routine march toward air-conditioning and iPhones. It has been a struggle. A blind struggle. That struggle continues today. But with a little more foresight.

The fascinating part of this history is that with every increase of complexity comes the mounting possibility of final victory over the Second Law and the tremendous natural burdens we have shouldered for 13.8 billion years.

chapter 11

The Anthropocene

Wherein the British start burning coal for steam power Mass production kicks off a blizzard of scientific and economic innovation • The rest of the world endeavors to catch up The world enters a new geological epoch known as the Anthropocene

The Industrial Revolution is another remarkable threshold of complexity that leads us to the immense transformations of modernity—whether we are discussing the Cambrian-style explosion of new technologies, revolutions of thought and doctrine, or the radical alteration of the lifeways of every human on this planet. To say nothing of how it opened the door to another geological epoch, the Anthropocene, in which humans are impacting the planet more rapidly and drastically than any single species in 3.8 billion years of life. The Anthropocene is a geological period that follows the Holocene (the period that began at the end of the last ice age). The term is derived from anthropos, the Greek for human.

We are now living at unprecedented levels of complexity in the history of the known Universe. In terms of structural intricacy, the unified global system of modernity contains an unprecedented number of people (8 billion at time of writing), who are all potential innovators in a system of collective learning. And these human minds are united by almost instantaneous communication, transportation, and unprecedented levels of literacy. Sustaining this web of knowledge are immensely intricate networks of trade, supply, laws, energy production, and a wider diversification of labor than ever before. In terms of energy flows, the free energy rate density of society has increased from an average of 100,000 erg/g/s in the Agrarian Era to 500,000 erg/g/s in the industrial nineteenth century, to 2 million erg/g/s in developed societies today.

The Second Great Divergence

The first key ingredient was the harnessing of fossil fuels for industrial production. Fossil fuels include coal, oil, and gas. They are so-called because they are actually the remains of living things that perished between 10 and 600 million years ago. Coal is made from the giant trees that fell to the ground starting 350 million years ago and got compressed by plate tectonics to form hard, thick layers of coal in rock beds. When burned, coal released the aggregated energy of billions of plants. Thus, fossil fuels far outstripped the energy output of human labor, animal labor, or the burning of wood when harnessed by industrial machinery. This powered the Industrial Revolution of the eighteenth and nineteenth centuries, and still powers much of the human energy grid today.

Oil similarly forms from single-celled creatures—and some multicelled creatures—that died hundreds of millions of years ago and were compressed by tectonic pressure into a form of sludge. Or pockets of gas, which is a by-product of the fossilization process of oil, when the pressure forces out all the residual gas inside the organisms.

The Industrial Revolution began in Great Britain in the eighteenth century. The continued refinement of the steam engine between 1712 and 1775, faster production of textiles in spinning machines compared to handweaving, the better refinement of iron in larger quantities: All these set off the initial spark of mass production. Britain’s textile industry drove down the price of cotton textiles by 100 percent between 1750 and 1800. Britain became the world’s leading iron and steel producer by 1820. Coal production increased by 600 percent between 1750 and 1870. Already by 1800, the rate of British manufacturing was three times higher than that in any agrarian state on Earth. Despite its tiny population, this made Britain the richest nation on the planet.

Farming was no longer as dominant an area of British society. By 1750, roughly 50 percent of the British economy was built on commercial ventures. Between 1750 and 1850, the number of farmers dropped from 60 percent of the population to 30 percent of the British population. A great diversification of labor followed in the nineteenth century, with more specialists such as engineers, lawyers, scientists, and entrepreneurs contributing to collective learning than ever before. This set off a further explosion of innovation. A similar phenomenon occurred in every nation that has industrialized.

Early 19th-century ironworks in Merthyr Tydfil, Wales

Britain’s lead continued to grow until roughly 1880, when it produced 23 percent of the world’s goods, despite it being tiny in terms of population (approximately 2 to 2.5 percent of the world’s total population in 1880). By comparison, in 1880, China represented 30 percent of the world’s population but only produced 12 percent of the world’s manufactured goods, whereas in 1800 it had produced about 33 percent of the world’s manufactured goods, roughly proportionate to its population size as an agrarian economy.

The World Tries to Catch Up

The British had a head start on industrialization over the rest of the world by at least a few decades (in some cases over a century). Britain was able to hold out against Napoleon, his allies, and the United States in the Napoleonic Wars and War of 1812, defeated the once mighty China in the First Opium War of 1839–42, and gradually forged the largest empire in human history.

With the advantages of industrialization becoming more and more apparent, other countries endeavored to replicate it. Belgium was already industrializing in the 1820s and 1830s. France began industrializing in the 1840s but with mixed success—only achieving 8 percent of the world’s total manufacturing compared to Britain’s 23 percent in 1880. They caught up later. Kind of. Prussia began industrializing in the 1850s, with the other German states lagging behind, but after unification in 1871, they pursued industrialization with gusto. Germany would surpass Britain’s industrial capacity in the 1910s and ’20s. Industrial capacity levels and the incidence of the two world wars are no accident.

The United States was the first power to clearly surpass Britain in terms of industrial production. After the end of the Civil War in 1865, the United States invested in a period of settlement in the west and heavy industrialization in the north, and let vast numbers of immigrants into the country. By 1880 the population had grown to 50 million, outstripping Britain in numbers, and the United States produced 15 percent of the world’s manufacturing goods. By 1900, the US population had grown to 76 million people, and it produced 25 to 30 percent of the world’s manufacturing. Britain was eclipsed and the United States’ lead would only increase.

The modern ingredients for superpower status were clear: have the largest population size possible, provided it was fully industrialized and developed. It is why the nations numbering 1.5 billion people dominate the other 6.5 billion today, and why nations such as China and India continue to industrialize in earnest. Imagine if 1.4 billion Chinese were as industrialized as 330 million Americans today.

Beyond the West were two other early industrializers eager to even the score and maintain a prominent place on the global stage. Russia tried to industrialize in the nineteenth century, but in 1900 only 5 percent of the population were industrial workers and the Russian share of total global production was only 8.9 percent, despite it having a population of 136 million people. It would require World War I, the rise of the Soviet Union, and the bloody excesses of Stalin to force a greater degree of industrialization—and even then the total Russian world share of manufactured goods increased only marginally.

Japan was somewhat more successful. The Japanese embarked on a period of rapid modernization and industrialization after the Meiji Restoration of 1868. The central government invited in Western experts, crafted a fairly Western-looking constitution and heavily subsidized all attempts at factory production. By doing so, Japan transformed from a feudal society to a modern one within half a century. Japan had a fairly large population from which they could build a large industrial economy. However, in 1900, Japan made only 2.5 percent of the world’s industrial output, and this share did not grow significantly until after World War II. After that, the Japanese “economic miracle” allowed its large industrialized population to become incredibly wealthy and it still enjoys the position of third place in the world, after the United States and China, today.

The unification of the world zones, the power of fossil fuels, and the imbalance of trade and scientific advancement allowed larger empires than ever before to be forged, and vast swathes of land and the majority of the world’s population to be controlled by relatively small armed forces of Europeans, Americans, and Japanese. By 1914, roughly 85 percent of the world’s surface had fallen under foreign imperial control.

Two world wars and scores of revolutions have not really altered this imbalance. The United States and Soviet Union wielded immense imperial power (directly and indirectly) in the Cold War. The US has dominated the world stage since 1989. China is currently expanding its influence across Asia, Africa, Europe, Australasia, and the Americas with rapid success. Even the French retain an often overlooked but significant amount of imperial influence in West Africa. The bulk of the world’s nations remain dominated by a few. Anyone who thinks the age of empires ended in the mid-twentieth century ought to look again. Empire is simply conducted more by stealth and with slightly better PR.

The Great Acceleration

From 1870 to 1914, the average annual rate of growth of the world’s exports was 3.4 percent and the average annual rate of growth of GDP per capita was 1.3 percent. The disastrous period of the two world wars from 1914 to 1945 saw the average annual rate of growth of exports shrink to 0.9 percent and the average annual rate of growth of GDP per capita to 0.91 percent. Thereafter, the nuclear bomb made warfare between Great Powers too costly. As a mildly ironic result of the creation of the most devastating weapons in world history, the period 1945 to the present has been one of the most “peaceful” (relatively speaking) in world history for at least 5,500 years. Possibly far longer, when one considers the skirmishes and raids of Early Agrarian societies, and the 10 percent murder rate of foraging societies stretching back 315,000 years to the birth of Homo sapiens.

As such, the period 1945 to present has been one of unprecedented growth in terms of exports, GDP, population, and complexity. This period is known as the “Great Acceleration.” From 1945 to 2020, the average annual rate of growth of exports was 6 percent and the rate of growth of global GDP was an average of 3 percent. Let that settle. Most of the “busy work” of human complexity has happened in the past seventy years. Still within living memory for some.

Global GDP since 1940

Today the United States still holds the lead, with a population of approximately 331.9 million, producing roughly 13.6 percent of the world’s GDP. China now has 18.4 percent of global GDP from a still-industrializing population of approximately 1.4 billion. Of the next-largest economies, Japan is 3.4 percent, Germany 3 percent, and the much larger Russian population constitutes 3.4 percent of global GDP. The combined GDP of the United Kingdom, Australia, Canada, and New Zealand is 4.4 percent of global GDP, which may be of interest should they engage in CANZUK-based unification in the wake of Brexit. India has a large population of 1.39 billion and currently produces 6.95 percent of the world’s GDP as it lags behind China in industrialization. In regard to both China and India, the growth of their GDP is really just the adjustment back into proportion with their share of the world population, reversing the Second Great Divergence of the nineteenth century. Provided such enormous populations don’t provide an obstacle to further economic growth somewhere in the near future.

Globally, the world population has increased from 2.5 billion in 1945 to 8 billion today. It took 315,000 years for the world population to achieve its first billion people, it took 100 years for the second billion, and further billions were added every few decades. The Green Revolution from the 1930s to the 1960s produced a number of highly effective chemical fertilizers, pesticides, and artificially enhanced grain and rice, raising the global carrying capacity. While regions such as India and China experienced horrific famines in the nineteenth and early to mid-twentieth centuries, their populations have been able to explode since then, soaring into the billions.

The world’s GDP output was $2.7 trillion in 1914, $33.7 trillion in 1997, $63 trillion in 2008, and is $85 trillion at the time of writing. In terms of food production, total grain output has increased from roughly 400 million tons in 1900 to over 2 billion tons today. The amount of irrigated land increased from 63 million hectares in 1900 to 94 million hectares in 1950 and 260 million hectares today.

Within a very short amount of time, the world has more people producing more stuff than at any point in the last 315,000 years of human history, working in a global system more complex than anything in the past 13.8 billion years. We now live in a network of 8 billion potential innovators, within an instantaneous communications network of email and the internet. This bodes well for the acceleration of collective learning into the future, especially as more educational and career opportunities are created for the inhabitants of developing economies.

The Anthropocene

By several metrics humans are now the dominant environmental and geological force on the face of the Earth. Not since the Great Oxygenation Event 3 to 2.5 billion years ago have biological organisms had such a profound impact on the Earth’s evolution.

There is a debate about when the Anthropocene truly begins. Some date it to the start of agriculture 12,000 years ago, when the immense deforestation from clearing land for farming fields may already have increased carbon emissions, and when humans began terraforming landscapes and domesticating and breeding millions upon millions of new animal species. Most proponents of the Anthropocene concept do not consider these changes significant enough to constitute an entirely new geological era. Others date the start of the Anthropocene to the beginning of the Industrial Revolution circa 1750 or 1800, due to the increase of carbon emissions and the role of technology transforming the environment more than ever before. Others still place the start of the Anthropocene with the Great Acceleration, since most human growth has happened since 1945, and because of the commencement of nuclear weapons testing, which has disrupted the atomic clocks of decaying isotopes around the world.

In terms of pure annual rates of extinction, humans are responsible for an extinction rate as fast as any of the five mass extinctions that have occurred in the past 550 million years, causing some to say that humans are driving a sixth mass extinction in the Anthropocene. Beyond that, human use of fresh water has increased by ten times since 1900, which may threaten to completely dry up the Earth’s aquifers, upon which both human and other life depend. We have put 70 percent of the world’s coral reefs at risk. In the past seventy years, we have increased the carbon dioxide content of the atmosphere to over 400 parts per million, higher than anything in the past 3 million years. A lot of this seems to imply a tremendous influence on the Earth system, and none of it seems to bode particularly well.

On the issue of climate change, we have increased the average global temperature by about 1°C since the start of the Industrial Revolution, and we are approaching the same average temperature as the Medieval Warm Period a thousand years ago. If we cross the threshold of more than a 4°C increase in the average global temperature, we run the risk of melting the frozen methane stores in the oceans and in Siberia, kicking off a runaway greenhouse effect that could take us to a 5°C or 6°C increase. In the long term, these increases could reduce arable cropland, starving the population, obliterating still more biodiversity, and flooding many highly populous regions with rising seas.

Another concern in the Anthropocene is the sheer growth of the human population. Happily, industrialization seems to slow down population growth in developed and developing economies alike. Nevertheless, the world population is set to reach 9 billion people by 2050, and somewhere between 10 and 13 billion people by 2100. With most of that population growth happening in regions of the world that are poorest and least equipped to deal with overpopulation—primarily sub-Saharan Africa. This raises a lot of problems. Either we slow population growth by rapid industrialization or we don’t industrialize (good luck convincing Africa, India, and China)—and we run the risk of a Malthusian disaster occurring in regions already nearest to the margins. Already 65 percent of the world’s current global emissions are produced by the developing world. The only long-term solution seems to be technologies such as hydrogen fusion, which would flood the world with cheap sources of energy that had comparatively little environmental impact, so that the world’s poor could industrialize and raise their living standards to their heart’s content, without risking a global meltdown.

From a bird’s-eye perspective, it is supremely unsurprising that the first burst of growth following a new threshold of complexity should be followed by a period of strain. We saw it shortly after the adoption of agriculture. We are too early in the Anthropocene to have experienced severe strain. In every stage of evolutionary history, species have exhausted their environments and had to compete for resources and energy flows by adapting their traits. And, ultimately, complexity guzzles all energy flows in the Universe until energy is used up and complexity itself dies.

The question for humanity in the Anthropocene is whether we can innovate in time to avoid another collision with the carrying capacity and another period of horrific decline and mounting death. Whether in this Golden Age we shall ascend to even further heights or descend into an Iron Age of war, or a new Dark Age of obliteration.

That brings us to discussion of the future in the final chapter, in terms of the next few centuries, the next few million years, and the next trillion, trillion, trillion years in the life of the Universe.

part four

The Unknown Phase
present–10⁴⁰ years from now

chapter 12

The Near and Deep Future

Wherein humanity’s destiny in the Anthropocene is one of four broad possibilities • The natural future of the Universe sees complexity fade • The potential of complexity in the Deep Future may lead to the rise of supercivilizations • The end of the Universe will be either the Big Freeze, Big Rip, Big Crunch, or Big Save

The universe began as a white-hot speck of energy within which all the ingredients for everything we see around us—whether by our own eyes or by powerful microscopes and telescopes—already existed. According to the First Law of Thermodynamics, which states that nothing (on the Newtonian scale at least) is created or destroyed but only changes form, we are the Universe. Just a highly complex, conscious, and self-aware part of it. One totality. Looking at itself. That fact alone is worth celebrating. We have been given the gift, however flawed our vision, of looking into the great beyond. Not many clumps of atoms can claim that honor.

When the physical laws of the Observable Universe became coherent 10–35 seconds after the Big Bang, so too emerged tiny dots of unequally distributed energy. The Second Law of Thermodynamics began to force these dots to even out by sending energy from where there is more to where there is less in order to achieve a cosmos with equally distributed energy. Energy flows created stars, diverse chemicals, organisms, and societies. All complexity in the Universe was created, sustained, and increased in complexity by energy flows. From sunlight to photosynthesizing plants. From table to mouth. From gas pump to jet engine. In a Universe that is 99.9999999999999 percent dead, tiny dots in the cosmos have been getting progressively more complex. Regardless of where things go from here, we are lucky to be along for this part of the ride, where complexity is higher than at any point in the past 13.8 billion years. Not just lucky in a sentimental sense but a mathematical sense of several quintillion to one.

The overarching trend of universal history is complexity, and the overarching trend of human history is collective learning—which in turn increases complexity. Using these two trends, we can make some forecasts about the future on short and long timescales. This is somewhat rare in the field of historical studies. Moreover, it is only in the future where the trends of complexity and collective learning really bear fruit and make the meaning of the upward trend clear for the reader.

So where exactly is our story likely to go next?

Predicting the Future

When predicting the future, you must not predict one future but several. And then assess each scenario based on their plausibility. These multiple futures, regardless of their exact detail, fall on a spectrum.

1. Projected future: What science says is happening. Things play out how current trends suggest they play out. It is business as usual, where we assume no major change to variables or behaviors, and no dynamic discoveries. The projected future may not even be the most likely future, since new discoveries and changes in variables do eventually occur, but it forms an important baseline for our forecasting. For instance, a projected future would involve the outcome of greenhouse gas emissions and global industrial growth continuing at current rates.

2. Probable future: What science says could happen. Where variation or change within the bounds of known science indicates where trends might go. The probable future is the projected future’s margin for error, or margin for variation. A probable future refers to something that science already understands but that hasn’t yet come to pass: For example, transition to and heavier reliance on solar technologies and less reliance on fossil fuels.

3. Possible future: What science might discover. Where a discovery as yet unknown to science alters a future outcome, or where we can’t scientifically explain in detail how everything will work. We are not visionary engineers capable of predicting technological progress 200 years from now. Imagine how difficult it would have been in 1800 ce to predict the existence of the internet, or its societal effects. A possible future has an unknown variable like an algebra equation: “present + x = outcome.” In fact, like an algebra equation, we can use the known variables to get a clearer picture of what the value of x actually is. Major advances in AI or nuclear fusion or quantum computing innovations (which we do not yet know how to fully engineer) would fall into this category.

4. Preposterous future: What science says can’t happen. Where an outcome seems to openly defy the laws of known science, contradicting all available data or understanding. It plays an important role in prediction because it clearly defines what a possible future is by mere contrast. It prevents speculation about technology going too overboard. But it can also serve to predict technologies that are currently too mind-boggling. The Moon landing might have seemed preposterous to someone in 1800, before rocketry or even human flight. An example of a preposterous future today is a technology that defies the Second Law of Thermodynamics.

In fact, on a long enough timescale, complexity can turn the preposterous into the possible, then the probable, and even the projected. If nothing else, the only way to figure out the limits of the possible is by going beyond them to the impossible.

Analyzing the Near Future

It is actually easier to predict the Deep Future, which has timescales of billions and trillions of years, than it is to predict the Near Future on timescales of hundreds or thousands of years. This is entirely down to complexity. Cosmological changes in the wider Universe that take billions of years to occur deal with relatively simple systems and calculations. Provided we have the right data, we know how long the Sun will live and how long it will take Andromeda to combine with the Milky Way, despite the fact that those things are billions of years away. Humanity is a much more complex system. Each individual human is capable of billions of different behaviors. In aggregate of billions of people, this makes for quite the calculation—one that no supercomputer is capable of. It is very difficult to predict what inventions humanity will stumble upon, and how these inventions will affect people’s behavior in society. Finally, humanity’s interactions with nature (something that is also very complex) make it difficult to predict the rise of diseases or natural disasters.

Even though the events of the next century are difficult to predict, all the possible outcomes of the Near Future over the next 100 to 300 years fall into four broad categories. They relate to whether human complexity rises, stabilizes, gracefully decreases, or collapses.

1. Technological breakthrough: Where human society does not hit a limit to its current modes of production in the next 100 to 300 years and rates of innovation keep pace with growth of the human population. Perhaps it involves the economically viable distribution of nuclear fusion power, making energy cheap enough even for the poorest countries to develop, with an exponential increase on the limits of energy and production globally, and without the corresponding degradation of the biosphere that comes with fossil fuels. But such a breakthrough also includes those scenarios where humanity hands the reins of future complexity to artificial intelligence. That is, collective learning sets off another jump in complexity.

2. Green equilibrium: Where human society over the next 100 to 300 years does not develop a major technological breakthrough in the Near Future (by no means a guarantee, since the first agriculture and Industrial Revolution are 12,000 years apart) and lives within its means to avoid total degradation of the biosphere. This may include technological innovation at a smaller scale, along with some good planning, government policy, and a shift to more sustainable forms of production. Human complexity does not increase significantly, nor does it decrease.

3. Creative descent: Where human society invokes a form of policy that actually reduces human production and consumption in order to ward off environmental or demographic disaster. It is a deliberate unraveling of human complexity. Examples of scenarios within this category include radical population control and reduction, dismantling of heavy industry, restrictions on car and air travel, restrictions on energy consumption and production rather than their replacement with renewable forms, rationing of food and clothing, and so on. Over a long enough period of descent, human complexity more closely resembles the agrarian states of 300 years ago than society today.

4. Collapse: Involving every conceivable doomsday scenario. Environmental disaster, nuclear war, superbugs, an asteroid impact, or a super-volcanic eruption. This category covers every scenario where human complexity dramatically declines, regardless of the cause.

Take a moment and ask yourself which future is the most likely? Why? For nearly two decades, the public discussions about climate change have prompted a notable rise in pessimism in developed countries. After two years of a global pandemic that resulted, among other things, in job losses and a spike in mental health issues, that pessimism may well have increased.

However, on a long enough timescale, collective learning will prompt another breakthrough in technology. Human complexity simply has to endure the scenario that occurs for long enough without collapsing for this to take effect. In that sense, humanity’s great task in the twenty-first century is to survive it. In all likelihood, we shall, which means that complexity might continue to increase for many millennia to come—with all the astounding new breakthroughs that implies.

Speculative rendering of a hydrogen reactor

In the wider context of rising complexity in the Universe, what happens in the twenty-first century may determine whether the trend continues or ends here. In that sense, the generations alive today and those that will be born in the next few years stand at a pivotal moment in history. It is a period where human actions will have a magnified impact, much more than any king, peasant, farmer, or forager spread across the last 315,000 years. In a very real material and temporal sense, what you do in your life matters, and potentially may echo into the future—in a way that very few individual actions have done before.

The “Natural” Deep Future

Analysis of the Deep Future falls into two broad streams. The first is the “natural” projected/probable futures of the Earth and the Universe, where higher complexity like biology or society have no impact on the processes of cosmology. The second stream is a series of possible/preposterous futures where complexity continues to increase for millions, billions, and even trillions of years beyond the current stage of human technology on Earth to the point where the wider cosmos is affected and manipulated by us.

According to current data, here are the natural projected/probable things that will happen in the Deep Future.

1. 1 billion years from now, death of the biosphere: Mass extinction events happen every 100 million years on average. But so far they have not yet succeeded in ending the world, just in wiping out a large percentage of existing species. The Deep Future is much more certain. In about a billion years, the Sun will begin to exhaust its fuel. Its luminosity will increase, CO₂ levels will decrease, and this means plants on Earth over the following years will find it harder and harder to do most forms of photosynthesis and thus sustain complex life on our tiny rock. Life would struggle and decline from the 1-billion-year mark onward. That’s nearly twice the amount of time that separates us from the Cambrian Explosion 541 million years ago. That’s a great deal of time for multicelled species to continue to evolve and change for a period of time nearly double what separates us from our jawless fish vertebrate ancestors. Even if humans go extinct, it is entirely possible that another species capable of collective learning could evolve during that time and then in a few hundred thousand years match or surpass our current level of complexity.

2. 3 to 7 billion years from now, death of the Earth and the Sun: At the 3-billion-year mark, the Sun will grow larger and larger until it boils the surface of the Earth dry. Once we get to an Earth’s surface with a temperature greater than 100°C (212°F), we can be pretty sure that’s it for life on Earth. Perhaps some single-celled organisms could still exist in the cracks of the Earth, but that is a clear decline of complexity and the end of the tale in our biosphere. Then the Sun will grow so large it will engulf the Earth, burning and absorbing whatever is left. The planet itself will be destroyed. The Sun may also bloat up to destroy Mars. But it will never get so large that it goes beyond that, leaving the Asteroid Belt and the gas giants largely unscathed. After that, the Sun will shrink back and eventually extinguish itself. If our descendants are still around in such a massive number of years, we are likely to be incredibly advanced in technology to the point of being godlike. We will either have left the Earth to terraform and live on the moons of Jupiter and Saturn, or we may well have macro-engineered the Sun so it has a replenished supply of hydrogen to burn, or we may have left the solar system for other planets, abandoned the galaxy entirely, or evolved to somehow not require a planet to live on at all.

3. 200 billion years from now, end of the Golden Age of Astronomy: As dark energy continues to accelerate the expansion of the Universe past the speed of light, we would no longer get to see the light from other galaxies. If we were to lose the knowledge of Big Bang cosmology, our galaxy would be all we’d see. Or think exists. We’d revert to the idea that the Universe had no start date, is static and eternal. The Milky Way would be our entire Universe. That is why a number of scientists refer to the current age where we can see evidence for the Big Bang, and can see other galaxies, as the Golden Age of Astronomy. We are lucky to have been born at such an early stage in the Universe, where, relatively speaking, the cosmos is still in its infancy, being only 13.8 billion years old in a Universe that will live on for many trillions of years.

4. 100 trillion years from now, end of stars: Once the Universe is trillions of years old, all new star formations will have ceased in all the galaxies of the Universe, and only the smallest slow-burning stars will still be burning. By the time we reach 100 trillion years from now, the last of these tiny, slow-burning stars will have died. At this point there will be no conventional energy flows to sustain life on planets, and it will become difficult for any moderately advanced seafaring societies to find enough energy flows to sustain or increase their complexity. One alternative would be to use the radiation that comes from black holes, but this does not emit in such generous amounts as a star. The saving grace of this projection is the astounding lengths complexity could have reached after trillions of years of collective learning (or whatever more rapid process supersedes it).

5. 10⁴⁰ years from now, heat death of matter: This is a 1 with thirty-nine zeros, or 10 duodecillion years from now. Or to put it another way, a trillion multiplied by a trillion, multiplied by another trillion, plus four more zeros. Or to put it yet another way, nearly three times the length of time that separates us from the end of stars. At this point, not only will stars have disappeared but the very fabric of planets and asteroids will have crumbled. All molecular combinations in the Universe will have long since decayed and only singular atoms will remain. Except these will have gradually decayed into simpler and simpler atoms too. Once we are down to just hydrogen atoms, these too will decay back into energy and the Universe will be nothing but a void filled with weak radiation becoming more and more evenly distributed thanks to the Second Law of Thermodynamics. The energy flows that created complexity so far in our story will have finished their work and all complexity in the Universe will have come to an end. This is what I meant when I said that the Second Law is at once the creator and destroyer of worlds. What we will have left is a blank eternity, with no change, no events, no history. Not just the end of the world, but the end of our story. The end of all history. About 10⁴⁰ years from now, even black holes will have emitted all their radiation and evaporated into thinly distributed energy as well. This scenario is known as the “Big Freeze” and is the projected end to the history of complexity in the Universe according to our current data. This is built on the idea that the Universe will continue accelerating and expand forever.

There are also two probable futures for the end of the Universe, if we observe new rates of expansion in the Universe that alter the data we use to make predictions. If the Universe is accelerating faster in expansion than we currently observe, then we have the “Big Rip” scenario, where the Universe expands so quickly it increases the space between galaxies, then overpowers the force of gravity and tears galaxies apart, then overpowers the nuclear forces that hold atoms together, and rips stars, planets, and organisms apart. This could happen in as little as 20 billion years from now. I say “little,” but that is still a heck of a long time.

The second probable future is the “Big Crunch,” where the acceleration of the expansion of the Universe actually slows down and reverses itself, eventually squeezing all galaxies in the Universe back together, and then further back into the white-hot singularity with which our story began. If this sets off yet another Big Bang, this leads to the corollary “Big Bounce” scenario, where the Universe expands again and is reborn over and over. Very poetic and appealing. Data doesn’t currently reflect this, but if the expansion of the Universe slowed down and reversed itself, this could take somewhere between 50 and a few hundred billion years.

As grim as the “Big Freeze” scenario may sound, with its “dying with a whimper” aesthetic, it actually gives complexity the maximum amount of time (trillions upon trillions upon trillions of years) to continue to increase and find a solution to the mortality imbued in the Universe by the Second Law of Thermodynamics. In that sense, we should actually be popping the champagne that the “Big Freeze” thus far seems to be the most likely outcome of our story.

The Deep Future of Complexity

Consider how “young” the 13.8-billion-year Universe is in terms of the 100 trillion years it will exist before all the stars burn out, and the trillions upon trillions upon trillions of years before the heat death of matter. Consider the tiny amount of time that biological complexity has existed on Earth (3.8 billion years) and the even more infinitesimal amount of time that humanity has existed in literate states and societies (5,500 years). Finally, consider how far collective learning and scientific progress has accelerated in the past 200 years.

That is such a small percentage of the amount of time that the Universe will exist that it is negligible. It is not even worth expressing in a percentage, given all the zeros that will go in front of it. And if complexity continues to accelerate (as it currently is), then once we start to consider where it could go in thousands or millions of years, to speak nothing of billions or trillions, then a highly advanced society could conceivably impact the natural evolution of the Universe.

Assuming that complexity continues to increase, this outcome is not only possible but it gradually becomes probable or even projected.

Yet it is almost impossible to predict what such advanced complexity would look like. Humans have difficulty speculating what technology will look like a decade from now, much less what it will look like on the timescale of thousands or millions of years. But there is one way in which we can gain an idea of just how complex and powerful those supercivilizations would be someday.

At the beginning of this book, we explored a metric for complexity—the density of energy flows that create, sustain, and increase complexity. The Sun achieves 2 erg/g/s, an average photosynthesizing organism 900 erg/g/s, a dog 20,000 erg/ g/s, human foraging societies 40,000 erg/g/s, agrarian states 100,000 erg/g/s, nineteenth-century industrial society 500,000 erg/g/s, and society today 2 million erg/g/s. With a quantifiable metric such as this, we are able to project how complex supercivilizations would be in the Deep Future, and even estimate how long it would take us to reach that point.

With each increase in energy flows came an increase in the structural intricacy of complexity: from a blob of hydrogen atoms to a single cell with DNA, to multicelled organisms composed of a network of trillions of cells, to the networks of humans, their domestic animals and all our machines that form a society. Also, at each increase of energy density comes the ability of humans, at least, to consciously manipulate the laws of physics and alter the environment around them to ensure their continued survival.

Without having the faintest idea of what science or miraculous inventions would arise in such supercivilizations, the trends we have so far observed in our story imply that complexity could become so advanced that it would start influencing the structure of galaxies and cosmological evolution itself.

Supercivilizations

In 1964, Russian astronomer Nikolai Kardashev proposed a scale by which we could evaluate advanced civilizations based on how much energy they harnessed. The various stages on this scale are measured by harnessing the equivalent of all the energy of a planet, star, or galaxy. Note that does not necessarily mean that a planet, star, or galaxy must be the actual source of such energy, but simply that a supercivilization has somehow generated the equivalent of such energy.

1. Type I Civilization (Planet): In the Anthropocene, humans are actually quite close to harnessing the energy equivalent of an entire planet. We are currently a “0.7” civilization or higher. So if we project a little into the future, our average free energy rate density would be 2,600,000 erg/g/s. In fact, that is such a small increase in average energy flows for society one can quite adequately speculate what such a society would look like: a planet without much larger a population, with more abundant energy sources to sustain their complexity (for example, a population of 10 billion with nuclear fusion reactors all living at a standard of living akin to the developed world today or better). If we project the accelerating rate of increasing complexity for humanity from the foraging era to today, the calculation indicates that humanity will achieve a Type I civilization in 300 years or less. Purely by looking at the numbers, humanity’s future looks fairly bright. Assuming we can keep complexity from backsliding. This is precisely why the current generations alive today are so pivotal in our story.

2. Type II Civilization (Star): At this point, we have moved from projected and probable futures to the possible futures where science does not yet have the precise knowledge to explain what technology would get us to this stage. The stage at which humanity (or whatever we turn into) harnesses the energy equivalent of a star may conjure up images of a Dyson sphere. This is where we surround a star with panels that absorb all the energy it gives off, rather than the small fraction of the energy it throws off into the entire Universe and hits plants or solar panels or other energy sources here on Earth. The free energy density of a supercivilization that harnesses the energy equivalent of a star is approximately 70,200,000,000 erg/g/—a major leap forward in complexity compared to modern society. And considerably more structurally intricate and capable of manipulating the surrounding environment and/or the fundamentals of physics in the Universe. That is roughly the same degree of difference in complexity that separates a single-cell organism from a World War II Spitfire engine. It is distinctly possible by this point that humans may be “trans-human” or “post-human.” Perhaps humans will have managed to reverse the effects of biological aging, or even uploaded their consciousnesses to computers to live on forever, either as a collective consciousness or individual cyborgs, with such advanced calculating power that collective learning, communication, and new inventions blaze along at blinding speed. Again, according to the current rate of acceleration of complexity, this would take us another 25,000 years at most. 25,000 years ago, human foragers were spread across Africa, Europe, Asia, and Australasia. It is roughly twice the space of time that separates us from agriculture. In terms of the total life expectancy of complexity in the Universe, even 25,000 years is an insignificant fraction of trillions upon trillions upon trillions of years. Even if we just consider the 100 trillion years where stars will still burn, that is 0.00000000025 percent of the time we would have to reach this stage.

What these numbers make clear is something astrobiologists and SETI-enthusiasts (those engaged in the search for extraterrestrial intelligence) already suspected: That it may take billions of years for complexity to get started in the Universe, but once it gets going, the time between each breakthrough gets smaller and smaller and smaller.

This leaves an insane amount of time for complexity to rise somewhere in the Universe—even if it doesn’t happen with our particular species.

Dyson sphere

3. Type III Civilization (Galaxy): If our hypothetical supercivilization finds that harnessing the power of a single star isn’t enough to manipulate the most fundamental laws of physics in the Universe, then they could always move on to harness the energy equivalent of the 200 to 400 billion stars that exist in the Milky Way galaxy. Such a powerful supercivilization would have 14,000,000,000,000,000,000,000,000 erg/g/s (14 septillion) in free energy density. That is greater in terms of complexity than the difference between a single subatomic particle and modern society. Such a supercivilization would essentially make our entire society and its powers look as complex as a quark. At this point we are talking about a society that has indisputably godlike powers to the point that it could probably manipulate an entire galaxy, if not the fundamental laws of the Universe itself, to suit its interests. If we use the same rate of acceleration of complexity, as massive as this number is, this could be achieved in less than 100,000 years. The same amount of time that separates us from Homo sapiens first migrating out of Africa. Even if these projections are off, physicists have previously estimated it would take between 5 and 50 million years for us to reach every solar system in the galaxy (assuming it is impossible to move faster than the speed of light). Or roughly the same amount of time that separates us from our last common ancestor with chimpanzees or with primates. Even 50 million years is a tiny fragment of the amount of time life on Earth has existed, much less the length of time that stars and galaxies will continue to exist.

If we literally harness the stars in a galaxy to achieve such power levels, we may well have to move stars around into some sort of “energy grid,” This is called galactic macro-engineering. If there is extremely advanced life elsewhere in the Universe that has already beat us to this point, we may be wrong in looking for radio signals from other societies. We may want to be looking among the 400 billion galaxies out there for signs of galactic structures that seem to have no natural explanation.

4. Type IV Civilization (Universe): We are now firmly in the realm of the preposterous future. While it may be physically possible to travel across the Milky Way galaxy, we would need some physics-defying technology to enter every single galaxy in the Observable Universe. If somehow this was achieved, however, we would harness approximately 6,000,000,000,000,000,000,000,000,000,000,000,000 erg/g/s (6 undecillion). There is no point of comparison for complexity here. We exhausted that with Type III civilizations. Nothing exists in the Universe so far that is so simple or so complex that we could contrast this in complexity to our current society. But given we have a numerical value, we can still calculate how long it would take us to reach this level. The results of the calculation are surprising. Assuming we can overcome the many physical and technological barriers with our previous godlike Type II and Type III civilizations, we could achieve Type IV in 200,000 years or less. According to this calculation, we’d go from our current Type 0.7 to a Type IV civilization in roughly 325,000 years. Just a little bit more than the period of time that Homo sapiens has been known to exist, and an extremely small fragment of time during which complexity can exist in the Universe. Even if these calculations are way off and the acceleration of complexity slows down significantly somewhere along the line, we can afford to be off by almost nine orders of magnitude before all the stars in the Universe burn out.

It is highly unlikely a supercivilization would need to harness this much power in order to achieve environment-manipulating ability to bend or break the physical laws of the Universe. It is highly likely such an ability would already be achieved at Type II or Type III.

5. Type V Civilization (Multiverse): Since we have come this far, we might as well go all the way. Assuming that a so-called Multiverse, as described in chapter 1, exists, and that it is possible to somehow traverse an eternity of inflationary space and unite all the energy flows from universes (where there exists such a thing as energy) in some sort of network (which would require us to thoroughly bend the properties of space and time), a Type V civilization harnesses all the energy flows of all the universes out there. Unfortunately, it is impossible to give a free energy number for this. Not just because the number would be insanely large. The number may well be infinite if the number of universes in the Multiverse is infinite. And without a finite number, it is impossible to project how long it would take, since traversing an infinite amount of universes would take an infinite amount of time. In that sense, if complexity could ever possibly get that far, we’d achieve what is essentially a “singularity” of complexity, where it runs toward infinity, past an event horizon of invention, where anything and everything is possible.

If the statement that we probably wouldn’t need to go this far to manipulate the fundamental properties of our Universe applies to Type IV civilizations, then that goes infinitely more times over for a Type V.

The “Big Save”

We have so far covered the three outcomes for the “natural” end of the Universe, where complexity has no impact on cosmological evolution: the Big Freeze, the Big Rip, and the Big Crunch/Bounce. Presumably all advanced civilizations in these scenarios don’t get much further than their own planets and eventually just go extinct. Which anyone will tell you is distinctly possible.

But the alternative futures where complexity continues to accelerate and does not suddenly stop at some point reveals one final endgame for our universal story. The scenario where a supercivilization that is a Type II, Type III, or Type IV actually grows so capable at manipulating its surrounding environment that it can somehow defy the Second Law of Thermodynamics and extend the life of complexity beyond its natural end date. In other words, the “Big Save.”

Given how quickly such a supercivilization could be reached, relative to the current age of the Universe or how much time the Universe has to exist in the Big Rip, Big Crunch/Bounce, and especially the Big Freeze scenarios, it is not unreasonable to add this possibility to the list.

Consider that in the last 635 million years that multicellular species have existed on Earth, at least one species out of an estimated 10 billion of them has produced collective learning to such a degree that societies were created. And most of that work was done in the past 12,000 years. Many astrobiologists agree that there could be up to 300 million habitable planets in the Milky Way galaxy. Assuming they all produce multicelled life (which they wouldn’t), that still would mean that an organism capable of collective learning would be unlikely to arise somewhere else in the Milky Way. However, when you also factor in the number of galaxies in the Observable Universe (approximately 400 billion), if you assume an average of 300 million habitable planets per galaxy, then the odds of another species being capable of becoming a supercivilization get quite a lot higher. And when you consider that there are trillions of years for such a species to arise again, when it took only 13.8 billion for us to arrive, the odds get overpowering. Even if humanity goes extinct somewhere in the Near Future (a possibility one can sense simply by turning on the news these days), there are good odds that a Type II, Type III, or Type IV Civilization could arise elsewhere in the Universe.

That is why the Big Save has to be considered in any horizon scan done for the endgame of the Universe, alongside the much more predictable natural endings.

In a Big Save scenario, we would attain either a Type II, III, or IV supercivilization (whatever was required technologically) and engage in one of three activities to prolong our complexity beyond the projected natural end of the Universe.

1. Escape: Assuming a Multiverse exists, we could simply leave for a universe that wasn’t quite so old or whose physical properties did not include the Second Law of Thermodynamics killing complexity by exhausting all energy flows.

2. Manipulate: Assuming a Multiverse does not exist or it is physically impossible to travel to other “coffee cup rings” on the beige table of the cosmos, a powerfully complex supercivilization might be able to manipulate the fundamental properties of the Universe (or rewrite them) in order to defy the Second Law of Thermodynamics. This seems to be the most likely case. A form of technology that generates perpetual motion (locally or universally) in order to undo the natural end of things.

3. Create: Most compatible with the Big Crunch, but not exclusive of the Big Freeze or Big Rip, if we could somehow manipulate space-time, we’d simply re-create the Big Bang, but precoded with conditions that produce physical laws and a distribution of matter and energy much friendlier to complexity than our own Universe.

All of the Big Save scenarios fall into the realm of the “preposterous” future, since they require not just an invention of something we don’t currently understand (a “possible” future) but achieving something that currently science says would be physically impossible. Yet it is only by riding the line of the preposterous that we find out what truly is possible.

If we look at the short amount of time it would take to achieve the level of a supercivilization, the long life ahead of complexity in the Universe and the immense complexity of those supercivilizations as shown by the numbers, it is worth bearing in mind. Things that would have seemed preposterous to humans living only a few centuries ago—instantaneous communication, traveling faster than the speed of sound or landing on the Moon—have been achieved by modern society. The demand on us isn’t that heavy: just to stick around for another 20,000 to 300,000 years and see what might happen.

The Answer May Not Be 42

I write at a time of extreme hardship and pessimism globally. Our population is experiencing strain (not entirely due to a pandemic but certainly worsened by it) and the worst political factionalism in living memory. A person of an anxious disposition may think this sounds suspiciously and dangerously like the downturn of a secular cycle.

It is therefore with great pleasure that I can talk not only about the Anthropocene but the end of the Universe with a great deal of optimism, buoyancy, and hope. The same patterns that have propelled us through the history of all existence seem to imply good and honest chances of surviving not only in the Near Future but into the Deep Future as well. And not just surviving but thriving. Perhaps even unraveling more of the great mysteries of the Universe. That is the supreme potential of human society, knowledge, and endeavor. It is extremely valuable.

Our actions in this day and age may hold the secret to launching a magnificent array of astounding things, which, on the timescales of the history of the Universe, are very close to hand indeed. And if any amount of optimism is to be applied to longevity technology or transhumanism, it is possible that either we or our children will be able to take part in that great adventure firsthand. That is the tremendous gift that all the exertions of the past have handed to us and that we may pass on to others.

We have explored at a leap and a bound the history of 13.8 billion years. But this story may only just be beginning.

Be brave, be good to each other.

Acknowledgments

I would like to thank David Christian for training me, giving me innumerable opportunities, and sticking by me in good and bad times, particularly in the most current disasters brought on by the pandemic.

I would also like to thank my parents, Susan and Greg Baker, for their boundless support and patience, and for supporting me in pursuit of a rather unusual field.

I’d like to thank Jason Gallate for the crucial moral support these past several months and for reading through drafts of this book. You literally saved my life.

In that respect I’d also like to thank Karen Stapley and Matt Diteljan for reading through drafts of this book and giving useful feedback that vastly improved its quality.

Lastly, I’d like to thank Milo. He knows why.

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Image Credits

Illustrations on pp. 10, 18, 29, 30, 32, 63, 120, 122, and 139 by Aira Pimping

Illustrations on pp. 103, 108, 111, 136, 157, and 184 by Alan Laver

p. 9 NASA: WMAP Science Team/Science Photo Library

p. 20 NASA/JPL-Caltech/R. Hurt (SSC/Caltech)/Wikimedia Commons

p. 22 Inductiveload/Wikimedia Commons

p. 34 Mikkel Juul Jensen/Science Photo Library

p. 40 Mark Garlick/Science Photo Library

p. 41 Gary Hincks/Science Photo Library

p. 54 CNX Openstax/Wikimedia commons

p. 68 Nicolas Primola/Shutterstock

p. 69 Sebastian Kaulitzki/Alamy

p. 70 Liliya Butenko/Shutterstock

p. 72 Gwen Shockey/Science Photo Library

p. 74 Junnn11/Wikimedia Commons

p. 74 Nobumichi Tamura, Stocktrek Images/Alamy

p. 76 Richard Bizley/Science Photo Library

p. 77 Michael Long/Science Photo Library

p. 79 tinkivinki/Shutterstock

p. 81 Sebastian Kaultzki/Science Photo Library

p. 85 Universal Images Group North America LLC/Alamy

p. 86 Bjoertvedt, Kitty Terwolbeck/Wikimedia Commons

p. 93 S. Entressangle/E. Daynes/Science Photo Library

p. 96 DK Images/Science Photo Library

p. 128 Rebecca Rose Flores/Alamy

p. 134 Asian and Middle Eastern Division/New York Public Library/Science Photo Library

p. 145 E Pluribus Anthony, Cogito ergo sumo, F l a n k e r/Wikimedia Commons

p. 146 Lewis H. Morgan/Wikimedia Commons

p. 148 Belsky/Wikimedia Commons

p. 160 Wikimedia Commons

p. 163 Theodor de Bry/Wikimedia Commons

p. 164 Gary Todd/Wikimedia Commons

p. 167 Bristol Central Reference Library

p. 169 Wikimedia Commons

p. 170 Garlan Miles/Wikimedia Commons

p. 178 Alphonse Dousseau/Wikimedia Commons

p. 198 Science Photo Library/Alamy

p. 209 Kevin Gill/Wikimedia Commons

Index

A  |  B  |  C  |  D  |  E  |  F  |  G  |  H  |  I  |  J  |  K  |  L  |  M  |  N  |  O  |  P  |  Q  |  R  |  S  |  T  |  U  |  V  |  W  |  Y  |  Z  |

NOTE: Page references in italics refer to figures and photos.

abolitionism, ref 1

Aboriginal population, ref 1, ref 2

Abu Hureya (Mesopotamia), ref 1

Achaemenid Empire (480 bce), ref 1

adenine, ref 1

aerobic cells, ref 1

Africa; see also individual names of countries:

Afro-Eurasia zone, defined, ref 1

and Age of Exploration, ref 1

Anthropocene Epoch, ref 1, ref 2

human foragers of, ref 1, ref 2, ref 3, ref 4

human migration from, ref 1, ref 2

melanin of skin, ref 1

placentals in, ref 1

primate evolution in, ref 1, ref 2

slavery, modern-day, ref 1

slave trade, ref 1, ref 2

trap of sedentism, ref 1

Afro-Eurasia:

Age of Exploration, ref 1

agrarian states and zone of, ref 1

and ecological imperialism, ref 1, ref 2

population and early agriculture, ref 1

Silk Roads, ref 1, ref 2, ref 3

Age of Explorations, ref 1, ref 2, ref 3, ref 4; see also unification of world zones

agrarian states, ref 1

complexity in, ref 1

“conventional history” origin, ref 1

Early Agrarian Era, ref 1, ref 2, ref 3

early cities of, ref 1, ref 2, ref 3

empires, rise and fall, ref 1, ref 2, ref 3

evolution of, ref 1, ref 2

population and carrying capacity of, ref 1

printing in, ref 1

secular cycles of, ref 1, ref 2, ref 3

and Silk Roads, ref 1, ref 2

world beyond, ref 1, ref 2

writing in, ref 1, ref 2, ref 3

agriculture, ref 1; see also agrarian states

in China, ref 1, ref 2, ref 3

“conventional” history and rate of change, ref 1

Early Agrarian Era and disease, ref 1, ref 2

and ecological imperialism, ref 1, ref 2, ref 3

energy flows captured from, ref 1, ref 2, ref 3

in Fertile Crescent, ref 1, ref 2, ref 3

fertilizer, ref 1, ref 2, ref 3

First Great Divergence, ref 1, ref 2

“gardens of Eden,” ref 1, ref 2

Industrial Revolution and decline of, ref 1

in Indus Valley, ref 1

irrigation, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7

power and hierarchy of, ref 1

societal formation around, ref 1, ref 2

timeline, ref 1, ref 2

and trap of sedentism, ref 1, ref 2

Akkadian Empire (Mesopotamia), ref 1

Aksum, ref 1

Albertosaurus, ref 1

Albion, ref 1

alcohol, ref 1

Allosaurus, ref 1

Amargasaurus, ref 1

Americas; see also individual place names:

agrarian states and zone of, ref 1, ref 2

Anthropocene Epoch, ref 1

ecological imperialism in, ref 1, ref 2, ref 3

human foragers of, ref 1

placentals in, ref 1

population and early agriculture in, ref 1

unification of world zones, ref 1, ref 2, ref 3, ref 4, ref 5

amino acids, ref 1

Andromeda, ref 1, ref 2

Animalia kingdom, ref 1

animals; see also primate evolution:

avian dinosaurs (Jurassic), ref 1

domestication of, ref 1, ref 2

herbivores (Jurassic), ref 1

placental and marsupial mammals (Cretaceous), ref 1

terrestrial Arthropods, ref 1

warm-blooded, origin of, ref 1

Animate Phase (3.8 billion–315,000 years ago), ref 1

explosions and extinctions, ref 1 (see also explosions and extinctions)

life and evolution, ref 1 (see also life and evolution)

primate evolution, ref 1 (see also primate evolution)

Ankylosaurus, ref 1, ref 2

Anomalocaris, ref 1, ref 2

Anthropocene Epoch:

defined, ref 1, ref 2

and Great Acceleration, ref 1, ref 2, ref 3

industrialization and superpowers’ emergence, ref 1

origin of, ref 1

Second Great Divergence, ref 1, ref 2, ref 3

timeline, ref 1

ants, ref 1

Arabia, ref 1, ref 2

Arabian Desert, ref 1

Archean eon, ref 1, ref 2

archosaurs, ref 1

Arkarua, ref 1

Arthropods, ref 1, ref 2, ref 3, ref 4

Asia; see also Middle East; individual names of countries:

Afro-Eurasia zone, defined, ref 1

Indus Valley, ref 1

Asteroid Belt, ref 1, ref 2, ref 3

asteroids, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6

atoms, ref 1

Australasia; see also Australia; individual names of Asian countries:

agrarian states and zone of, ref 1, ref 2

Anthropocene Epoch, ref 1

early agriculture and population, ref 1

Australia:

Aboriginal population, ref 1, ref 2

Anthropocene Epoch, ref 1

Australasia, defined, ref 1

foraging and fire stick farming, ref 1

human migration to, ref 1

marsupials in, ref 1

Shark Bay, ref 1

Australopithecines, ref 1, ref 2, ref 3, ref 4

avian dinosaurs, ref 1

Aztecs, ref 1, ref 2

Banpo (China), ref 1

Belgium, ref 1

Bering Strait, ref 1

beryllium, ref 1

Big Bang, ref 1

absolute first date after, ref 1, ref 2, ref 3, ref 4

biological complexity from, ref 1, ref 2, ref 3

and cosmic microwave background, ref 1, ref 2

events of, ref 1

knowledge of, ref 1, ref 2, ref 3

matter and energy created from, ref 1

and Multiverse, ref 1

and Near and Deep Future, ref 1, ref 2, ref 3

and Observable Universe, ref 1, ref 2

space and time “before,” ref 1

temperature of, ref 1, ref 2, ref 3, ref 4

timeline of, ref 1, ref 2

Big Crunch/Bounce, ref 1, ref 2, ref 3

Big Freeze, ref 1, ref 2, ref 3

Big Rip, ref 1, ref 2, ref 3

Big Save, ref 1

biosphere, death of, ref 1

bipedalism, ref 1, ref 2, ref 3, ref 4

birds, avian dinosaurs and, ref 1

Bi Sheng, ref 1

Black Death, ref 1, ref 2

black holes, ref 1, ref 2

bonobos, ref 1

bottom-up power, ref 1

brain:

cephalization process, ref 1

dopamine and alcohol, ref 1

evolution of human foragers, ref 1

and primate evolution, ref 1, ref 2, ref 3, ref 4, ref 5

Brazil, ref 1

bubonic plague, ref 1

buffalo, ref 1, ref 2

burial (Early Agrarian Era), ref 1

Cambrian Explosion, ref 1, ref 2, ref 3

Canada, ref 1

CANZUK unification, ref 1

carbon, ref 1

carbon dioxide, ref 1

Carboniferous Period, ref 1, ref 2

Caribbean islands, ref 1, ref 2

carrying capacity of population, ref 1; see also population statistics

Central Africa, ref 1

cephalization, ref 1

Chaco Canyon, ref 1, ref 2

Charnia, ref 1, ref 2

Charon, ref 1

chemistry; see also Earth; life and evolution; individual names of chemicals:

of Archean oceans, ref 1

of stars, ref 1

chimpanzees, ref 1, ref 2, ref 3, ref 4

China:

agriculture origin in, ref 1, ref 2, ref 3

Anthropocene Epoch, ref 1, ref 2, ref 3, ref 4, ref 5

“barbarian” invaders, ref 1

Black Death, ref 1

Chinese exploration, ref 1

and ecological imperialism, ref 1

famine (1333–37), ref 1

First Great Divergence, ref 1

during Industrial Revolution, ref 1

printing in, ref 1

Silk Roads, ref 1, ref 2

slavery, ref 1

chloroplasts, ref 1

cholera, ref 1

Chordates, ref 1

climate change, modern-day, ref 1

coal, ref 1, ref 2, ref 3

collapse (Near Future), ref 1

collective learning:

in agrarian societies, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6

defined, ref 1, ref 2

of supercivilizations, ref 1

Columbus, Christopher, ref 1

complexity, ref 1

in agrarian states, ref 1

biological complexity, ref 1, ref 2, ref 3

and collective learning, ref 1

“conventional” history and rate of change, ref 1

Deep Future of, ref 1

energy density and birth of, ref 1, ref 2, ref 3

energy from Big Bang, ref 1, ref 2

energy metrics, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6

galaxies, origin of, ref 1, ref 2

increasing complexity as pattern of history, ref 1, ref 2, ref 3

mechanics of, ref 1, ref 2

progress vs., ref 1, ref 2

and Second Law of Thermodynamics, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8, ref 9

and stars, ref 1

timeline, ref 1

Congo, ref 1

Congo River, ref 1

continents, drift of, ref 1, ref 2

convection flows, ref 1

“conventional history,” ref 1

core, ref 1, ref 2

corn, ref 1, ref 2

Cortés, Hernán, ref 1

“cosmic latte,” ref 1

cosmic microwave background (CMB), ref 1

creative descent, ref 1

Cretaceous Period, ref 1, ref 2, ref 3, ref 4

crisis (population), ref 1

crocodilians, ref 1

crust, ref 1, ref 2

Cultural Phase (315,000 years ago–present), ref 1

agrarian states, ref 1 (see also agrarian states)

agriculture origin, ref 1 (see also agriculture)

Anthropocene, ref 1 (see also Anthropocene Epoch)

and collective learning, ref 1

human foragers, ref 1 (see also humans)

primate evolution and social learning, ref 1, ref 2

unification of world zones, ref 1 (see also unification of world zones)

cynodonts, ref 1

cytosine, ref 1

da Gama, Vasco, ref 1

Darwin, Charles, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7

Deep Future; see Near and Deep Future

del Cano, Juan Sebastian, ref 1

deoxyribonucleic acid (DNA), ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8

depression (population), ref 1

Devonian Period, ref 1, ref 2

Dias, Bartolomeu, ref 1

diet; see agriculture

differentiation, ref 1

dinosaurs, ref 1, ref 2

disease:

in Age of Exploration, ref 1, ref 2

Black Death, ref 1, ref 2

in Early Agrarian Era, ref 1

and ecological imperialism, ref 1, ref 2

plagues of agrarian states, ref 1, ref 2

and slave trade, ref 1

division of labor, ref 1, ref 2

Dyson sphere, ref 1

Early Agrarian Era; see agrarian states

Earth, ref 1

Archean eon of, ref 1

crust, mantle, core of, ref 1, ref 2

crust and plate tectonics, ref 1

death of, ref 1

Hadean eon of, ref 1

life origin on, ref 1

and Milky Way’s origin, ref 1

modern-day biomass, ref 1

Moon formation, ref 1, ref 2, ref 3, ref 4

ocean formation, ref 1, ref 2

rock composition of, ref 1, ref 2

and solar system’s origin, ref 1, ref 2

and Sun’s origin, ref 1

timeline of, ref 1

ecological imperialism, ref 1, ref 2, ref 3, ref 4

Ediacara, ref 1

Ediacaran Period, ref 1, ref 2

Egypt, ref 1

electromagnetism, ref 1

elliptical galaxies, ref 1, ref 2

empires, agrarian states and, ref 1, ref 2, ref 3

energy; see also complexity:

agriculture origin and energy flows captured, ref 1, ref 2, ref 3

Big Bang and origin of, ref 1, ref 2, ref 3, ref 4

biological complexity for life and evolution, ref 1, ref 2, ref 3

created by Big Bang, ref 1

of Deep Future, ref 1

density and birth of complexity, ref 1, ref 2, ref 3

First Law of Thermodynamics, ref 1, ref 2, ref 3

future needs for, ref 1

galactic macro-engineering, ref 1

geothermal, ref 1

manufactured, ref 1

metrics of, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7

and predation, ref 1

Second Law of Thermodynamics and, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8, ref 9, ref 10

of Sun, ref 1, ref 2

of supercivilizations, ref 1

entrenched hierarchy, ref 1

Eridu (Sumer), ref 1

Eris, ref 1

Essentials of Agriculture and Sericulture (China), ref 1

eternal inflation, ref 1

Ethiopia, ref 1

eukaryotes, ref 1

Europa (moon of Jupiter), ref 1

Europe; see also individual names of countries:

Afro-Eurasia zone, defined, ref 1

Anthropocene Epoch, ref 1

European exploration, ref 1, ref 2, ref 3

human foragers of, ref 1

evolution; see life and evolution; primate evolution

exoplanets, ref 1

expansion (population), ref 1

explosions and extinctions, ref 1

Cambrian Period, ref 1, ref 2

Carboniferous Period, ref 1, ref 2

Cretaceous Period, ref 1, ref 2, ref 3

Devonian Period, ref 1, ref 2

Ediacaran Period, ref 1, ref 2

higher complexity and faster change (635 million to 66 million years ago), ref 1, ref 2

Jurassic Period, ref 1

Ordovician Period, ref 1

and Pangea, ref 1, ref 2

Permian Period, ref 1, ref 2

prokaryotic species extinction, ref 1

Silurian Period, ref 1, ref 2

sixth mass extinction of Anthropocene, ref 1

Triassic Period, ref 1

Ferdinand of Aragon, ref 1

Fertile Crescent, ref 1, ref 2, ref 3

fertilizer, ref 1, ref 2, ref 3

financial issues; see also trade and industry:

complexity of agrarian states, ref 1

First Great Divergence, ref 1

GDP, ref 1, ref 2

of Silk Road trade, ref 1

unification of world zones, ref 1

fire stick farming, ref 1

First Great Divergence, ref 1, ref 2

First Great Migration, ref 1

First Law of Thermodynamics, ref 1, ref 2, ref 3

First Opium War, ref 1

fossil fuels, ref 1

France, ref 1, ref 2, ref 3

fungi, ref 1, ref 2, ref 3

future; see Near and Deep Future

galactic macro-engineering, ref 1

galaxies:

and energy from Big Bang, ref 1 (see also complexity)

in Observable Universe, ref 1, ref 2

origin of, ref 1, ref 2

and space expansion, ref 1

Galaxy (Type III) supercivilization, ref 1, ref 2, ref 3

“gardens of Eden,” ref 1, ref 2

gas, ref 1, ref 2

GDP (gross domestic product), ref 1, ref 2

genocide, ref 1

Germanic invasions, ref 1

Germany, ref 1, ref 2

Golden Age of Astronomy, ref 1

Golden Horde, ref 1

gorillas, ref 1

gravity, ref 1, ref 2

Great Acceleration, ref 1, ref 2, ref 3

Great Apes, ref 1

Great Bombardment, ref 1

Great Britain, ref 1, ref 2

Great Famine of Europe, ref 1

Great Migrations, ref 1, ref 2, ref 3

Great Oxygenation Event, ref 1, ref 2

green equilibrium, ref 1

Green Revolution, ref 1

guanine, ref 1

Gutenberg, Johannes, ref 1

Hadean Eon, ref 1

Haikouichthys, ref 1

Haumea, ref 1

Hawaiian Islands, ref 1

heat death, ref 1, ref 2, ref 3

helium, ref 1, ref 2, ref 3, ref 4

herbivores, evolution, ref 1

Hercules A, ref 1

Holocene Epoch, ref 1

Homo antecessor, ref 1

Homo erectus, ref 1, ref 2, ref 3

Homo ergaster, ref 1

Homo habilis, ref 1

Homo heidelbergensis, ref 1

Homo sapiens:

evolution, ref 1

as human foragers, ref 1, ref 2, ref 3, ref 4

Near and Deep Future of, ref 1, ref 2

horses, ref 1, ref 2, ref 3

Hubble, Edwin, ref 1

humans, ref 1; see also agrarian states; agriculture; Anthropocene; collective learning; Homo sapiens; population statistics; unification of world zones

and agriculture origin, ref 1, ref 2, ref 3, ref 4

Chordates as ancestors of, ref 1

collective learning and innovation, ref 1, ref 2, ref 3

DNA shared with animal and plant species, ref 1

and ecological imperialism, ref 1

in era of agrarian states, ref 1

and Great Migrations, ref 1, ref 2, ref 3

from Home erectus to Home sapiens, ref 1, ref 2

in ice ages, ref 1, ref 2

and sexual dimorphism, ref 1

social anxiety origin, ref 1

in stone age, ref 1, ref 2, ref 3, ref 4

timeline, ref 1

hydrogen:

atom structure, ref 1

and Big Bang, ref 1, ref 2, ref 3

early life and evolution, ref 1, ref 2

stars and exhaustion of, ref 1

ice ages, ref 1, ref 2

Ichthyostega, ref 1

Inanimate Phase (13.8–3.8 billion years ago), ref 1

Big Bang, ref 1 (see also Big Bang)

and complexity, ref 1 (see also complexity)

Earth’s origin, ref 1 (see also Earth)

timeline of, ref 1, ref 2

Incan Empire, ref 1, ref 2, ref 3

India:

Afro-Eurasia, defined, ref 1

Anthropocene Epoch, ref 1, ref 2

human foragers of, ref 1, ref 2

unification of world zones, ref 1, ref 2

Indochina, ref 1, ref 2

Indonesia, ref 1, ref 2, ref 3

Industrial Revolution, ref 1, ref 2, ref 3, ref 4, ref 5; see also trade and industry

infanticide, ref 1

innovation; see tools and innovation

insects:

ants (Cretaceous), ref 1

bees (Cretaceous), ref 1

of Carboniferous, ref 1, ref 2

interglacial periods, ref 1

iron, ref 1, ref 2, ref 3, ref 4

irregular galaxies, ref 1, ref 2

Isabella of Castile, ref 1

Islam, ref 1, ref 2, ref 3, ref 4

Japan, ref 1, ref 2, ref 3

Jericho (Middle East), ref 1

Jupiter, ref 1, ref 2

Jurassic Period, ref 1, ref 2

Kardashev, Nikolai, ref 1

Korea, printing in, ref 1

Kuiper Belt, ref 1

labor; see also agriculture; slavery; tools and innovation:

of animals, ref 1, ref 2

division of, ref 1, ref 2

human labor in Early Agrarian Era, ref 1

language and communication:

and evolution of human foragers, ref 1

and primate evolution, ref 1, ref 2, ref 3

printing evolution, ref 1

writing origin, ref 1, ref 2, ref 3

Last Glacial Period, ref 1, ref 2

Late Heavy Bombardment, ref 1, ref 2

Late Jurassic Period, ref 1

lava, ref 1

lenticular galaxies, ref 1, ref 2

life and evolution, ref 1

biological complexity and energy for, ref 1, ref 2, ref 3

chemicals needed for, ref 1

and DNA, ref 1, ref 2, ref 3

eukaryotes, ref 1

eyes, ref 1

feathers, ref 1

hooves, ref 1

melanin of skin, ref 1

multicellularism, ref 1

plate tectonics and effect on, ref 1

prokaryotes, ref 1, ref 2, ref 3

and RNA, ref 1

and Snowball Earth, ref 1, ref 2

teeth, ref 1

timeline of, ref 1

“tooth and claw” evolution, ref 1

vestigial limbs, ref 1

warm-blooded animals, ref 1

light-years, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6

lithium, ref 1

lower mantle, ref 1, ref 2

Magellan, Ferdinand, ref 1

Makemake, ref 1

mammals:

and primate evolution, ref 1, ref 2

protomammals, ref 1, ref 2

protomarsupial mammals, ref 1

proto-placental mammals, ref 1

marine life:

aquaculture origin, ref 1

Devonian sea scorpion, ref 1, ref 2

early mammals, ref 1

mollusks’ eyes, ref 1

Ordovician species explosion of, ref 1

Silurian jawed fish, ref 1, ref 2

Mars, ref 1, ref 2, ref 3

mathematics, ref 1

matter, Big Bang origin of, ref 1, ref 2, ref 3, ref 4

Mayans, ref 1

Medieval Warm Period, ref 1

Meiji Restoration, ref 1

Mercury, ref 1, ref 2

Mesoamerica, ref 1, ref 2

Mesopotamia, ref 1, ref 2, ref 3, ref 4

Middle East:

Fertile Crescent, ref 1, ref 2, ref 3

Second Great Migration, ref 1

Sumer, ref 1

Milky Way:

of Near and Deep Future, ref 1, ref 2, ref 3, ref 4

origin of, ref 1, ref 2, ref 3, ref 4

size of, ref 1, ref 2

Ming dynasty, ref 1, ref 2

mitochondria, ref 1

molecules:

chemistry of stars, ref 1

Earth and life origin, ref 1

water structure, ref 1

monogamy, ref 1

Moon, ref 1, ref 2, ref 3, ref 4

Morocco, ref 1

Mount Toba (Sumatra, Indonesia), ref 1

multicellularism, ref 1

Multiverse, defined, ref 1

Multiverse (Type V) supercivilization, ref 1

mutation, ref 1

Napoleonic Wars, ref 1

Native Americans:

and ecological imperialism, ref 1, ref 2

and slavery, ref 1, ref 2, ref 3

natural selection, ref 1, ref 2; see also life and evolution

Neanderthals, ref 1

Near and Deep Future, ref 1

and Big Bang, ref 1, ref 2, ref 3

and Big Save, ref 1

Deep Future, “natural” (projected/probable), ref 1

Deep Future of complexity, ref 1

forecasting (projected/probable/possible/preposterous futures), ref 1

Near Future analysis, ref 1, ref 2

optimism for, ref 1

supercivilization concepts, ref 1, ref 2

timelines, ref 1, ref 2

Neolithic Period, ref 1

Neptune, ref 1, ref 2

Netherlands, ref 1, ref 2

neutrons, ref 1

neutron stars, ref 1

New Guinea, ref 1

Newton, Isaac, ref 1

New World monkeys, ref 1, ref 2, ref 3

New Zealand, ref 1, ref 2

Nigeria, ref 1

nitrogen, ref 1

nuclear forces, ref 1, ref 2

nucleobases, ref 1

nucleus/nuclei, ref 1

Observable Universe, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6

oceans, origin of, ref 1, ref 2

Oganesson, ref 1

oil, ref 1, ref 2

Old World monkeys, ref 1, ref 2, ref 3

Olmecs, ref 1

Omo remains, ref 1

Oort Cloud, ref 1

Orange Dwarfs, ref 1

Ordovician Period, ref 1

organelles, ref 1

Origin of Species (Darwin), ref 1

Ottoman Turks, ref 1

outgassing, ref 1, ref 2

oxygen:

early life and evolution, ref 1, ref 2

explosions and extinctions due to, ref 1, ref 2, ref 3

Great Oxygenation Event, ref 1, ref 2

Pacific Islands, ref 1

Pacific zone:

and agrarian states, ref 1, ref 2

unification of world zones, ref 1

Pakistan, ref 1

Paleolithic Period, ref 1, ref 2, ref 3, ref 4, ref 5

Pangea, ref 1, ref 2

Penzias, Arno, ref 1

Permian Period, ref 1, ref 2, ref 3

Persia, ref 1, ref 2

phosphorous, ref 1

photolysis, ref 1

photosynthesis, ref 1, ref 2, ref 3, ref 4

physics; see also energy:

Big Bang and fundamental forces of, ref 1

of black holes, ref 1

First Law of Thermodynamics, ref 1, ref 2, ref 3

matter and energy origin, ref 1

number of physical laws, ref 1

quantum realm, ref 1, ref 2, ref 3, ref 4

Second Law of Thermodynamics, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8, ref 9, ref 10

Pikaia, ref 1

Pizarro, Francisco, ref 1

plagues; see disease

planets, ref 1; see also complexity

individual names

Planet (Type I) supercivilization, ref 1

plants; see also agriculture:

flowering (Cretaceous), ref 1

grasses (Cretaceous), ref 1

terrestrial, early, ref 1

plate tectonics, ref 1

Pluto, ref 1

pluvial episode (Triassic), ref 1

Pneumodesmus, ref 1

Polo, Marco, ref 1

polyethylene, ref 1

polygyny, ref 1

population statistics; see also timeline:

of agrarian states, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8, ref 9

and agriculture origin, ref 1, ref 2, ref 3

and Anthropocene Epoch, ref 1, ref 2, ref 3

evolution of human foragers, ref 1, ref 2, ref 3, ref 4, ref 5

and unification of world zones, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6

Portugal, ref 1, ref 2

potatoes, ref 1

power and hierarchy; see also agrarian states; unification of world zones:

and agriculture origin, ref 1

entrenched hierarchy, ref 1

and evolution of primates, ref 1, ref 2

predation, ref 1, ref 2

primate evolution, ref 1

and bipedalism, ref 1, ref 2, ref 3, ref 4

bonobos, ref 1

chimpanzees, ref 1, ref 2, ref 3

and collective learning, ref 1

early mammals, ref 1, ref 2

gorillas, ref 1

Homo erectus, ref 1, ref 2, ref 3

Homo habilis, ref 1

New World monkeys, ref 1, ref 2, ref 3

Old World monkeys, ref 1, ref 2, ref 3

timeline, ref 1

projected/probable/possible/preposterous futures, defined, ref 1

prokaryotes, ref 1, ref 2, ref 3, ref 4

proteins, ref 1

Protestant Reformation, ref 1

protomammals, ref 1, ref 2

protomarsupial mammals, ref 1

protons, ref 1

proto-placental mammals, ref 1

protoplanets, ref 1

Proxima Centauri, ref 1

Prussia, ref 1

Pteridinium, ref 1

pterosaurs, ref 1

quantum realm, ref 1, ref 2, ref 3, ref 4

quartz, ref 1

Red Dwarfs, ref 1

Red Giants, ref 1

religion:

Catholic Church, ref 1

of Early Agrarian Era, ref 1

Islam, ref 1, ref 2, ref 3, ref 4

Protestant Reformation, ref 1

and slavery, ref 1

Renaissance, ref 1

reproduction and sexual behavior:

carrying capacity of population exceeded, ref 1 (see also population statistics)

eukaryotes and, ref 1

human foragers and society, ref 1

and primate evolution, ref 1, ref 2

and prokaryotes, ref 1, ref 2

ribonucleic acid (RNA), ref 1

ribosomes, ref 1

rice, ref 1

Russia, ref 1, ref 2, ref 3, ref 4

Sahara Desert, ref 1

sanitation, ref 1, ref 2, ref 3

Saturn, ref 1, ref 2, ref 3

sauropsids, ref 1

Scientific Revolution, ref 1

Scotland, ref 1

scribes (writing), ref 1, ref 2, ref 3

Second Great Divergence, ref 1, ref 2, ref 3

Second Great Migration, ref 1, ref 2, ref 3

Second Law of Thermodynamics, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7, ref 8, ref 9, ref 10

secular cycles, ref 1, ref 2, ref 3, ref 4, ref 5

sedentism, trap of, ref 1, ref 2

serfdom, ref 1

sexual dimorphism, ref 1, ref 2

Shark Bay (Australia), ref 1

Silk Roads, ref 1, ref 2, ref 3, ref 4

Silurian Period, ref 1, ref 2

silverback gorillas, ref 1, ref 2

sixth mass extinction, ref 1

slavery:

abolitionism, ref 1

African slave trade, ref 1, ref 2

in agrarian states, ref 1, ref 2

modern-day, ref 1

smallpox, ref 1

Snowball Earth (first), ref 1

Snowball Earth (final), ref 1

socialization:

agriculture origin, societal formation, ref 1, ref 2

division of labor, ref 1, ref 2

foraging life and society, ref 1

power and hierarchy, ref 1, ref 2, ref 3

social anxiety origin, ref 1

Sombrero Galaxy, ref 1

Song dynasty (960–1276 ce), ref 1

space, “before” Big Bang, ref 1

Spain, ref 1, ref 2, ref 3

spiral galaxies, ref 1, ref 2

Srivijaya kingdom, ref 1

Stalin, Joseph, ref 1

stars:

chemistry of, ref 1

and energy from Big Bang, ref 1 (see also complexity)

galactic macro-engineering, ref 1

life span of, ref 1

origin of, ref 1

timeline, ref 1

Star (Type II) supercivilization, ref 1, ref 2, ref 3, ref 4

static, ref 1

Stone Age, ref 1, ref 2, ref 3, ref 4

strain (population), ref 1

stromatolites, ref 1

Sumer, ref 1

Sun:

death of, ref 1

energy of, ref 1, ref 2

origin of, ref 1

photolysis, ref 1

photosynthesis, ref 1, ref 2, ref 3, ref 4

and solar system’s origin, ref 1, ref 2

as Yellow Dwarf, ref 1

supercivilizations (Types I–V), ref 1

Supergiants, ref 1

supernovas, ref 1

superpowers, emergence of, ref 1

Supersaurus, ref 1

symbiosis, ref 1, ref 2

synapsids, ref 1

Tang dynasty, ref 1

temperature:

of Big Bang, ref 1, ref 2, ref 3, ref 4

climate change, modern-day, ref 1

early life enabled by, ref 1

Medieval Warm Period, ref 1

and origin of stars, ref 1

and primate evolution, ref 1, ref 2, ref 3

Snowball Earth, ref 1, ref 2

Tenochtitlan-Tlatelolco, ref 1

Teotihuacan, ref 1

Tetrapoda, ref 1

tetrapods, ref 1, ref 2, ref 3

Theia, ref 1, ref 2, ref 3

therapsids, ref 1, ref 2

thymine, ref 1

Tiktaalik, ref 1

timeline:

agriculture, ref 1, ref 2

Anthropocene Epoch, ref 1

Big Bang, ref 1, ref 2

complexity, ref 1

Earth, ref 1

humans, ref 1

life and evolution, ref 1, ref 2

Near and Deep Future, ref 1, ref 2

stars, ref 1

unification of world zones, ref 1

Titan (moon of Saturn), ref 1

Titin (protein), ref 1

tools and innovation:

and agriculture, ref 1, ref 2, ref 3

axes used by Homo erectus, ref 1, ref 2

collective learning, ref 1, ref 2, ref 3

fire, ref 1, ref 2, ref 3, ref 4

Industrial Revolution, ref 1, ref 2, ref 3, ref 4

of Near Future, ref 1, ref 2

and primate evolution, ref 1, ref 2

seafaring in stone age, ref 1, ref 2

during Second Great Migration, ref 1

top-down power, ref 1

trade and industry; see also unification of world zones:

First Great Divergence, ref 1, ref 2

globalization, Medieval origin, ref 1

Great Acceleration, ref 1, ref 2

Industrial Revolution, ref 1, ref 2, ref 3, ref 4, ref 5

Second Great Divergence, ref 1, ref 2, ref 3

Silk Roads, ref 1, ref 2

trap of sedentism, ref 1, ref 2

Triassic Period, ref 1, ref 2

Triceratops, ref 1

trilobites, ref 1, ref 2

typhus, ref 1

Tyrannosaurus rex, ref 1, ref 2

unification of world zones, ref 1

agrarian states and zones, defined, ref 1, ref 2

Anthropocene origin, ref 1

Black Death, ref 1, ref 2

Chinese exploration, ref 1

ecological imperialism, ref 1, ref 2, ref 3, ref 4

European exploration, ref 1, ref 2, ref 3

First Great Divergence, ref 1, ref 2

and Silk Road trade, ref 1, ref 2, ref 3, ref 4

slave trade, ref 1, ref 2

timeline, ref 1

United Kingdom, ref 1; see also Great Britain

United States, ref 1, ref 2, ref 3, ref 4

Universe; see also Animate Phase; complexity; Cultural Phase; energy; Inanimate Phase; Near and Deep Future:

color of, ref 1

estimating age of, ref 1

Observable Universe, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6

shape of, ref 1

size of, ref 1, ref 2, ref 3, ref 4

Universe (Type IV) supercivilization, ref 1, ref 2, ref 3

unknown phase; see Near and Deep Future

upper mantle, ref 1, ref 2

Uranus, ref 1, ref 2

Uruk (Sumer), ref 1

Vatican Library, ref 1

vents, ref 1

Venus, ref 1, ref 2

villages, societal formation, ref 1, ref 2

violence; see also slavery:

in Age of Exploration, ref 1

of Early Agrarian Era, ref 1

and gender, ref 1

gunpowder origin, ref 1

and primate evolution, ref 1, ref 2

secular cycles of, ref 1, ref 2, ref 3

warfare in agrarian states, ref 1, ref 2, ref 3, ref 4

wars of nineteenth and twentieth centuries, ref 1

volcanoes, ref 1, ref 2, ref 3, ref 4, ref 5

War of 1812, ref 2

water:

and agrarian states, ref 1, ref 2

and agriculture origin, ref 1, ref 2, ref 3

irrigation, ref 1, ref 2, ref 3, ref 4, ref 5, ref 6, ref 7

modern-day threats to, ref 1

molecule structure, ref 1

oceans, origin, ref 1, ref 2

whales, ref 1

White Dwarfs, ref 1

Wilson, Robert, ref 1

Yellow Dwarfs, ref 1

Yucatán Peninsula, ref 1

zero energy vacuum, ref 1

About the Author

David Baker, PhD, is a history and science writer for SimonWhistler.com who holds the world’s first PhD in Big History (the emerging field that considers the entire history of the universe, from the Big Bang up until today), studying under David Christian. He has delivered award-winning lectures at Macquarie University and the University of Amsterdam, is a visiting lecturer at the University of Paris-Sorbonne, and wrote the YouTube series Crash Course Big History, hosted by John Green and his brother Hank Green in partnership with the Gates Big History Project. He lives in Sydney, Australia.

images davidcanzuk

The Shortest History of Our Universe: The Unlikely Journey from the Big Bang to Us
Copyright © 2022 by David Baker
Foreword copyright © 2022 by John Green
Pages 229–30 are a continuation of this copyright page.

Originally published in Australia as The Shortest History of the World by Black Inc. in 2022. First published in North America in revised form by The Experiment, LLC, in 2023.

All rights reserved. Except for brief passages quoted in newspaper, magazine, radio, television, or online reviews, no portion of this book may be reproduced, distributed, or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or information storage or retrieval system, without the prior written permission of the publisher.

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New York, NY 10010-4658
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Library of Congress Cataloging-in-Publication Data

Names: Baker, David (PhD in big History), author. | Green, John, foreword.

Title: The shortest history of our universe / David Baker ; foreword by John Green

Other titles: Unlikely journey from the big bang to us

Description: New York, NY : The Experiment, LLC, 2023. | Series: The shortest history series | Includes index.

Identifiers: LCCN 2022060242 (print) | LCCN 2022060243 (ebook)

Subjects: LCSH: Cosmology--Popular works.

Classification: LCC QB982 .B347 2023 (print) | LCC QB982 (ebook) | DDC 523.1--dc23/eng/20221220

eISBN: 9781615199747