Last Ape Standing: The Seven-Million-Year Story of How and Why We Survived Read online

  Contents

  Author’s Note

  Introduction

  Chapter One The Battle for Survival

  Chapter Two The Invention of Childhood (Or Why It Hurts to Have a Baby)

  Chapter Three Learning Machines

  Chapter Four Tangled Webs—the Moral Primate

  Chapter Five The Everywhere Ape

  Chapter Six Cousin Creatures

  Chapter Seven Beauties in the Beast

  Chapter Eight The Voice Inside Your Head

  Epilogue: The Next Human

  Acknowledgments

  Notes

  Bibliography

  Footnotes

  A Note on the Author

  By the Same Author

  Plate Section

  For Cyn. My compass and my Gibraltar.

  Author’s Note

  Despite its academic-sounding name, a good deal of brawling often goes on within the field of paleoanthropology. That it explores the deep past and counts on bits of ossified bone grudgingly revealed or scraped out of the earth doesn’t help the inexactness of the science, or the disagreements it generates. Although all researchers in the field work hard to bring the objectivity of the scientific method to their work, its nature involves a lot of guesswork. So while one scientist or group of scientists may think that the unearthed fossils of a particular creature demand that it be classified as a new species, others might feel just as strongly that it is simply a new example of a species that has already been discovered. Some scientists find good reason to have created the classification Homo antecessor, for example. Others, just as reputable, and just as thorough in their thinking, argue no such species ever existed.

  No one really knows. The evidence is too sparse and too random. We are making up these names as a convenient way of organizing the chaos of discovery over the past 180 years. It’s not as though the creatures themselves went by the nomenclatures we have made up. Nor can we comprehend what we don’t know. We can never say if we have discovered the fragmented evidence of 80 percent of our direct ancestors and cousin human species, or 1 percent.

  Too often, being human, we may give the impression we understand more than we do, or that we have just about figured it all out. We haven’t, as you will see. One of the reasons this book is relevant is because the human family tree, or more precisely, our very limited view of it, has changed so much in just the past five years.

  Advances in genetics, innovations in radiocarbon dating, together with plain old scientific creativity and elbow grease have greatly improved our guesswork and helped flesh out the discoveries we have made. There would be no hope, for example, of having even the remotest idea that a wisdom tooth and the end of a pinkie finger found in a Siberian cave three years ago belonged to an entirely new species of human (scientists call them Denisovans) with whom we and Neanderthals may share a common ancestor. This paltry evidence even revealed we mated with them! Nor would we have learned that billions of humans (including, very possibly, you) have Neanderthal mlood running in their veins. But we now know these astonishing things are true, even as they have turned assumptions once taken as gospel entirely on their heads.

  Still, despite these advances and the exciting discoveries they have made possible, the illumination of our past is a little like trying to find a set of car keys in the Sahara with a flashlight.

  I bring this up now to clarify a point: we don’t know exactly how many other human species have evolved over the past 7 million years—27 or 2700. We likely never will. But I have tried to arrive at an arguable and acceptable number that makes the larger point that, despite the disagreements that take place within the field, the story of how we came to be is a good deal more intriguing and complicated than we thought even a few years ago. And that makes the story even better.

  Introduction

  Over the past 180 years we have so far managed to stumble across, unearth, and otherwise bring to light evidence that twenty-seven separate human (hominin, to use the up-to-date scientific term)1 species have evolved on planet Earth. As you may have noticed, twenty-six of them are now no longer with us, done in by their environments, predators, disease, or the unfortunate shortcomings of their DNA. The lone survivor is a peculiar, and peculiarly successful, upright walking primate that calls itself, a little self-importantly, Homo sapiens sapiens, the wise, wise one. In most circles, we simply call them you and me.2

  Of all the varieties of humans who have come and struggled and wandered and evolved, why are we the only one still standing? Couldn’t more than one version have survived and coexisted with us in a world as big as ours? Lions and tigers, panthers and mountain lions, coexist. Gorillas, orangutans, bonobos, and chimpanzees do as well (if barely). Two kinds of elephants and multiple versions of dolphins, finches, sharks, bears, and beetles inhabit the planet. Yet only one kind of human. Why?

  Most of us believe that we alone survived because we never had any company in the first place. According to this thinking, we evolved serially, from a single procession of gifted ancestors, each replacing the previous model once evolution had gotten around to getting it right. And so we moved step by step (Aristotle called this the “Great Chain of Being”), improving from the primal and incompetent to the modern and perfectly honed. Given that view, it would be impossible for us to have any contemporaries. Who else could have existed, except our direct, and extinguished, antecedents? And where else could it all lead, except to us, the final, perfect result?

  This turns out to be entirely wrong. Of the twenty-seven human species that have so far been discovered (and we are likely yet to discover far more), a considerable number of them lived side by side. They competed, sometimes they may have mated, more than once one variety likely did others in either by murdering them outright or simply outcompeting them for limited resources. We are still scrounging and scraping for the answers, but learning more all the time.

  If we hope to place our arrival on the scene in any sort of perspective, it’s a good idea to remember that every species on Earth, and every species that has ever lived on Earth (by some estimates thirty billion of them), enjoyed a long and checkered past. Each came from somewhere quite different from where it ended up, usually by a circuitous, and startling, route. It’s difficult to imagine, for example, that the blue whales that now swim the world’s oceans, great leviathan submarines that they are, were once furry, hoofed animals that roamed the plains south of the Himalayas fifty-three million years ago. Or that chickens and ostriches are the improbable descendants of dinosaurs. Or that horses were once small-brained little mammals not much taller than your average cat with a long tail to match. And the Pekinese lapdogs that grace the couches of so many homes around the world can trace their beginnings to the lithe and lethal gray wolves of northern Eurasia.

  The point is, behind every living thing lies a captivating tale of how the forces of nature and chance transformed them, step by genetic step, into the creatures they are today. We are no exception. You and I have also come to the present by a circuitous and startling route, and once we were quite different from the way we are now.

  Theories about our ancestry have been amended often because new discoveries about how we came into existence keep emerging; several times, in fact, while this book was being written. But however it played out in the details, we know this: for every variety of human that has come and gone, including those we think we have identified as our direct predecessors, it has been a punishing seven million years. Survival has always been a full-time job, and the slipperiest of goals. (It still is for mos
t humans on the planet. More than four billion people—nearly two thirds of the human race—subsist each day on less than two dollars). But luckily, for you and me at least, while evolution’s turbulent dance rendered the last line of non–Homo sapiens DNA obsolete eleven thousand years ago, it allowed ours to continue until finally, of all the many human species that had once existed, we found ourselves the last ape standing.

  Not that we should rejoice at the demise of those others. We owe a lot to the fellow humans that came before us—hairier, taller, shorter, angrier, clumsier, faster, stronger, dumber, tougher—because every one of us is the happy recipient of all the more successful traits that our ancestors acquired in their brawl to keep themselves up and running. If today we were to make the face-to-face acquaintance of an Australopithecus afarensis or Homo ergaster or Paranthropus robustus, what would we see? Intelligence, fear, and curiosity is my guess, for starters. And they would see the same in us because we truly are kindred spirits.

  This has ensured that many of the deft genetic strategies that made those now departed human species once possible still remain encoded in the DNA that you and I have hauled with us out of the womb and blithely carry around each day into our personal worlds. The millions of these creatures who came and strove and passed through the incomprehensibly long epochs between their time on earth and the here and now are, after all, us, or at least some of them were. We are a marvelous and intriguing amalgamation of those seven million years of evolutionary experimentation and tomfoolery. If not for the hard planks of human behavior those others long ago laid down, we would be naught.

  So you can thank the lines of primates that in eons past found their way into Africa’s savannas, then to Arabia and the steppes of Asia, the mountain forests of Europe, and the damp archipelagoes of the Pacific, for genetic innovations like your big toe, your ample brain, language, music, and opposable thumbs, not to mention a good deal of your personal likes and dislikes, fascinations, sexual proclivities, desires, temper, charm and good looks. Human love, greed, heroics, envy, and violence all trace the threads of their origins back to the deoxyribonucleic acid of the humans who came before us.

  Some might wonder what sense it makes to rummage through the leavings of the past seven million years to try to piece together the story of our peculiar emergence. The payoff is that it’s the best way to understand why we do the startling, astonishing, sometimes sublime and sometimes horrible things we do. We owe it to ourselves to unravel the riddles of our evolution because we, more than any other animal, can. If we don’t, we stand no chance of comprehending who we really are as individuals or as a species. And only by understanding can we hope to solve the problems we create. To not understand how we came into this universe damns us to remain mystified by our mistakes, and unable to build a future that is not simply human, but also humane.

  This in itself, however, fails to answer the nagging question of why our particular branch in the human family managed to find its way to the present when so many others were shown the evolutionary door. Plenty of other human species had a good run; many considerably longer than ours. Some were bigger, some were stronger and faster, some even had heftier brains, yet none of those traits was good enough to see them through to the present. What events, what forces, twists, and evolutionary legerdemain made creatures like you and me and the other seven billion of us who currently walk the earth possible?

  Somehow only we, against all odds, and despite the brutal, capricious ways of nature, managed to survive … so far.

  Why?

  Our story begins once upon a time, a long time ago …

  Chip Walter

  Pittsburgh, Pennsylvania

  June 2012

  Chapter One

  The Battle for Survival

  DNA neither cares nor knows. DNA just is.

  And we dance to its music.

  —Richard Dawkins

  The universe houses, by our best count, one hundred billion galaxies. In one sector, a not very remarkable galaxy in the shape of a Frisbee with a bulge at the center spins pinwheel style through the immense void. One hundred billion suns reside in the Milky Way, each annihilating—at varying levels of violence—uncounted trillions of hydrogen molecules into helium. Along the edge of this disk, where the star clusters begin to thin out, sits the sun that we wake up to every morning. By some cosmic calculus that science has yet to decipher, the planet we call home came to rest at just the right distance away from that star, and with just the right makeup of atmosphere, gravity, and chemistry to have made an immense variety of living things possible.

  Our universe has been around roughly fifteen billion years; our sun, perhaps six; Earth has made four billion circuits around its mother star, and the life upon it has been ardently evolving during 3.8 billion of those journeys, give or take a few hundred million years. For the vast majority of that time anything alive on Earth was no larger than a single cell. Had we been around to see this life, we would have missed it since it is invisible to the naked eye. But of course, if it hadn’t come first, we, and everything else alive on Earth, would have been out of the question.

  No matter how hard we try, we cannot begin to fathom the changes, iterations, and alterations our planet has undergone since it first came to rest, collided and molten, in its current orbit. Our minds aren’t built to handle numbers that large or experiences that alien. And in this book we won’t try. Instead we will focus on a hiccup in that Brobdingnagian history, but a crucial hiccup, especially from your particular point of view—the past seven million years. Because that is when the first humans came into existence.

  Compared with the other smaller, rocky planets in our solar system, Earth has always been especially capricious. During its lifetime it has been hot and molten, usually wet, sometimes cold, at other times seared. Occasionally large sectors have been encased in ice; other epochs have seen it covered with gargantuan swamps and impenetrable rain forests inhabited by insects larger than a Saint Bernard. Deserts have advanced and retreated like marauding armies, while whole seas and oceans have spilled this way and that. Its landmasses have a way of wandering around like pancakes on a buttered griddle, so that the global map we find familiar today was entirely different a billion years ago and has spent most of the time in between resolutely rearranging itself, often with interesting results for the creatures trying to survive its geologic schemes.

  Charles Darwin and Alfred Russel Wallace figured out by the mid-nineteenth century that these incessant alterations explain why Earth has spawned so many varieties of life. Random revisions in the DNA of living things, together with erratic modifications in environments, have a way of causing, over time, whole new and astonishing forms of life to emerge. Darwin, when after years of thought and hand-wringing finally got around to writing On the Origin of Species, called this “descent by means of natural selection,” which was to say that creatures change randomly (by mechanisms unknown to him; he and everyone else in 1859 were ignorant of mutating genes or spiraling ladders of DNA) and either endure in their environment, or not. If the mutations that shift their traits help the organism to survive, he surmised, then it breeds more offspring and the species continues, passing the new traits on. If not—and this has been the case with 99.99 percent of all of the life that has ever evolved—then the life form is, as scientists like to say, “selected out.” Darwin figured that different environments favored different mutations, and over time—incomprehensibly long periods of time—different organisms diverged like the branches of a tree, each shoot putting increasing distance between the others around it until, eventually, you find your self with varieties of life emerging as different as a paramecium and Marilyn Monroe.

  So, though we may have started out with single prokaryotic cells and stromatolitic mats of algae nearly four thousand million years ago, eventually the world found itself brimming, in stages, with lungfish, slime mold, velociraptors, dodo birds, salmon and clown fish, dung beetles, ichthyosaurs, angler fish, army ants, big
horn sheep, and—after almost all of the time that ever was had passed—human beings—peculiarly complicated animals, with big brains, keen eyes, gregarious natures, nimble hands, and more self-aware than any other creature to have ever come down the evolutionary pike.

  Of the twenty-seven species of humans that we have so far found that once walked Earth, ours is the most favored line for the simple reason that, so far at least, we have avoided the genetic trash bin. Given evolution’s haphazard ways, we might just as well have ended up a blowhole-breathing water mammal, a round-eyed, nocturnal marsupial, or a sticky-tongue anteater obsessed with poking its wobbling proboscis into the nearest nest of formicidae.a We could even have become the formicidae for that matter.

  Or we might have become extinct.

  But as it turns out—and lucky for us—we emerged from the jungles of Africa, came to stand upright, clustered ourselves into close-knit packs, gave up our front paws for hands, grew thumbs, took up reformed, meat-eating diets, developed tools, and, in a remarkably short time—as evolutionary events go—rearranged the world right down to its molecules and right up to its climate. Today we are even manipulating the DNA that makes us possible in the first place—a case of evolution evolving new ways to evolve. (Think about that for a moment.)

  We did not pop out of the jungles of Africa in our current form like Athena from the head of Zeus, big-brained, tool-laden, and ready for modern life. We came in stages, part of a vast and jumbled experiment largely driven by our home planet’s fickle ways. Between six and seven million years ago Africa’s rain forests began to shrink slowly. Earth was a different place from today, but not radically so. If there were time-traveling, Earth-orbiting satellites to provide a global view of our planet then, it would look pretty much the same as the one we see on the Weather Channel today. India would be in place mostly, though still slowly plowing into Asia, creating the Himalayas. Australia would be roughly located where we find it now. The Mediterranean would be a touch larger. Partially submerged, the boot of Italy would not look quite so bootlike, and the Bosporus strait along with sectors of the Middle East would be inundated, though soon enough the closure of the strait at Gibraltar would transform the Mediterranean into a vast plain of salt flats, marshes, and brackish lakes.