A Brief History of Everyone Who Ever Lived Read online

  It’s upon these differences in populations that evolution can act, and it’s in these differences that we can follow the path of humankind, as we have roamed across land and oceans, and oceans of time, into every corner of the planet. Geneticists have suddenly become historians.

  A single genome contains a huge amount of uncurated data, enough to lay out plans for a human. But genomics is a comparative science. Two sets of DNA from different people contain much more than double that information. All human genomes host the same genes, but they all may be slightly different, which accounts for the fact that we are all incredibly similar, and utterly unique. By comparing those differences we can make inferences about how closely related those two people are, and when those differences evolved. We can now extend these comparisons to all humanity, as long as we can pull DNA from your cells.

  When the first complete human genome was published in 2001 to great fanfare, it was in fact a sketchy draft readout of most of the genetic material of just a few of us. To get this far had taken hundreds of scientists the best part of a decade, and had cost on the order of $3 billion, approximately $1 per letter of DNA. Just fifteen years later, things are emphatically easier, and the amount of data from individual genomes now is incalculable. As I write these words we have approximately 150,000 fully sequenced human genomes, and useful samplings from literally millions of people, from all over the world. Grand medical endeavors with accurate names like “The Hundred Thousand Genome Project” typify how easily we can now extract the data that we all store in our living cells. Here in the UK, we are seriously considering sequencing genomes of everyone at birth. And it’s not limited to the rigor of formal science or governmental medical policy: You can spit in a test tube and get a read-out of key parts of your own genome from an armada of companies that will tell you all sorts of things about your characteristics, history, and risk of some diseases, for just a couple of hundred dollars.

  We now have genomes of hundreds of long dead people too to slot into this grand narrative. The bones of an English king, Richard III, were identified in 2014 with a raft of archaeological evidence (Chapter 4), but the deal was royally sealed with his DNA. The kings and queens of the past are known to us because of their status, and because history is dominated by telling and retelling their stories. While genetics has enriched the study of monarchs, DNA is the ultimate leveler, and our newfound ability to extract the finest details of the living past has rendered this an examination of the people, of countries, of migration, of everyone. We can test, and verify or falsify, and know the histories of the people, not just the powerful or the celebrities of their day. Nobodies from the past are being elevated to some of the most important people who ever lived. DNA is universal and, as we’ll find out, being in a royal lineage might afford you divine rights over citizens, and the spoils that go with inherited power, but evolution, genetics, and sex are largely indifferent to nationalities, borders, and all that heady power.

  And we can look further still. The study of ancient humans was once limited to old teeth and bones and the ghostly traces of their lives left in dirt, but we can now piece together the genetic information of truly ancient humans, of Neanderthals and other extinct members of our extended family, and these people are revealing a new route to where we are today. We can pluck out their DNA to tell us things that could not be known in any other way—we can, for example, know how a Neanderthal person experienced smell.

  Retrieved after epochs, DNA has profoundly revised our evolutionary story. The past may be a foreign country, but the maps were inside us the whole time.

  The amount of data this new science is generating is colossal, phenomenal, overwhelming. Studies are being published every week that upend what has come before. In the penultimate stages of writing this book, the date of the great exodus from Africa may have shifted more than 10,000 years earlier than previously thought, following the discovery of forty-seven modern teeth in China. Then in the final stages it moved back by another 20,000 years with the detection of Homo sapiens DNA in a millennia-dead Neanderthal girl. These numbers are not much in evolutionary terms, ripples in geological time. But that is much more than the whole of written human history, and so the land continually and dramatically moves under our feet.

  The first half of this book is about the rewriting of the past using genetics, from a time when there were at least four human species on Earth right up to the kings of Europe into the eighteenth century. The second half is about who we are today, and what the study of DNA in the twenty-first century says about families, health, psychology, race, and the fate of us. Both parts are drawn from using DNA as a text to sit alongside the historical sources we have relied on for centuries: archaeology, rocks, old bones, legends, chronicles, and family histories.

  Although the study of ancestors and inheritance is as old as humans, genetics is a scientific field that is young, with a difficult short history. Human genetics was born as a means of measuring people, comparatively, such that the differences between them could be formalized as science, and used to justify segregation and subjugation. The birth of genetics is synonymous with the birth of eugenics, though at the time in the late nineteenth century, that word did not carry the same toxic meaning that it has now. There is no more controversial subject in all of science than race—people are different from each other, and the weight of those differences is something that has caused some of the deepest divisions and cruelest, bloodiest acts in history. As we will see, modern genetics has shown how we continue to get the whole concept of race so spectacularly wrong. Humans love telling stories. We’re a species that craves narrative, and more specifically, narrative satisfaction—explanation, a way of making sense of things, and the ineffable complexities of being human—beginnings, middles, and ends. When we started to read the genome, what we wanted to find there were narratives that tidied up the mysteries of history and culture and individual identity, that told us exactly who we were, and why.

  Our wishes were not satisfied. The human genome turned out to be far more interesting and complicated than anyone anticipated, including all the geneticists who remain ever more gainfully employed a decade on from the so-called completion of the Human Genome Project. The truth of this complexity and our lack of understanding is struggling to filter down into what we talk about when we talk about genetics. We once spoke of blood and bloodlines as a means of tying us to our ancestors and describing our familial selves. It’s no longer in the blood, it is in our genes. DNA has become a byword for destiny, or a seam running through us that seals our fates. But it is not. All scientists think that their field is the one that is least well represented in the media, but I’m a scientist and a writer, and I believe that human genetics stands out above all as one destined to be misunderstood, I think because we are culturally programmed to misunderstand it.

  Science is apt to reveal that much of the world is not how we perceive it, whether that is the cosmological, the molecular, the atomic, or the subatomic. These fields are distant or abstract compared with how we talk about families, about inheritance, about race, about intelligence, and about history. The baggage we carry, the subjectivity with which we naturally approach these quintessentially human characteristics is without equal. The gap between what science has revealed and how we talk about families and race is a chasm, because, as we shall see, things are not how we thought they were.

  There’s plenty of fabrication and mythmaking born of DNA as well. Genetics can certainly tell us who our closest relatives really are, and can reveal so many mysteries of our deep past. But you have far less in common with your ancestors than you may realize, and there are people in your family from whom you have inherited no genes at all, and who therefore have no meaningful genetic link to you, even though in a genealogical sense you are most definitely descended from them. I will show you that despite what you might have read, genetics won’t tell you how smart your kids will be, or what sports they should play, or what gender person they might fancy, or h
ow they will die, or why some people commit acts of heinous violence and murder. Just as important as what genetics can tell us is what it can’t.

  Our DNA is the very thing that has encoded brains sophisticated enough to be capable of asking questions about our own origins, and providing the tools to figure out how our evolution has proceeded. Changes in this strange molecule have accumulated and been recorded over time, waiting patiently for millennia for us to discover how to read it. And now we can. Each chapter in this book tells a different story about history and about genetics, of battles lost and won, of invaders, marauders, murder, migration, agriculture, disease, kings and queens, plague, and plenty of deviant sex.

  Above all, you are holding a history book. Some of the stories here are the history of genetics—with all its own convoluted twists and dark past—included to understand how we know what we now are discovering. Many of the stories are tales of nations, populations, a few known through celebrity or inheritance of power, but most are of the anonymous multitudes. We can pick through the bones of individual men, women, and children who through sheer chance died in uncommon circumstances, and turned out to be the people whose lives we would scrutinize forensically because in the preservation of their death they inadvertently gave up their DNA to us.

  Biology is the study of what lives and therefore what dies. It’s messy—wonderfully, frustratingly so—and imprecise and defies definitions. If you want to start at the beginning, which might seem like a very good place to start, then here is where our troubles begin.

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  Horny and mobile

  “There is no beginning, no middle, no end, no suspense, no moral, no causes, no effects. What we love in our books are the depths of many marvelous moments seen all at one time.”

  Kurt Vonnegut, Slaughterhouse-Five

  Vonnegut was half right. There is definitely no beginning, and if there is an end, it’s not in sight. We are always in the middle, and we are all missing links. Just like there was no absolute point when your life began, there was no moment of creation when our species began, no spark of life, no breath of God into the nostrils of an Adam molded in the red earth, no cracking of a cosmic egg. So it goes. Nothing living is fixed, and all creatures are four dimensional, existing in space, and also through time.

  Life is transition: The only things that are truly static are already dead. Your parents had parents, and theirs had parents, and so on, two by two, back through the whole of history, and prehistory. If you keep going back and back, your ancestors will slowly and inevitably become unrecognizable to you, via apes and monkeys, two-legged then quadrupedal, and ratty mammals and brutish beasts on land, and before them in wading sea creatures and fishy swimmers, and worms and weedy sea plants, and around two billion years ago, you don’t even need two parents, but just the binary fission of a single cell, one becomes two. Eventually, at the beginning of life on Earth around 4 billion years ago, you’re locked in a rock at the bottom of the oceans, inside the hot bubbling tumult of a hydrothermal vent. This geologically slow, incremental change is like a color chart, where pixel-by-pixel white becomes black, whether it’s the gap from reptile to mammal, or from four-legged to upright. On occasion there will be a splash of color thrown into the mix, but for the most part, the pathway to your ancestors creeps rather than jerks,* and all of it gray in its depths.

  Life on Earth has been continuous in that time, and we are a dot on that gray continuum. Conjure up that image of a hairy monkey-like ape on all fours, to the left of a crouching ape, to the left of a hunched stooping ape, to the left of an upright, modern bearded man-ape like us wielding a flint-tipped spear with his right leg cocked coyly forward to protect us from seeing his immodest instruments of biological transition. This iconic image implies something that we now know is untrue. We just don’t know the pathway of the apes that led to us. We know many of the creatures en route, but the map is full of gaps and smears. The second untruth is that there is a direction to our evolution, to our bipedal gait, and our big beefy brains, and our tools and culture. With that arrow we are to infer progress, from simplicity to an inescapable advance into the erect future, an inevitable cognitive revolution of the mind.

  Alas, we are no more or less evolved than any creature. Uniqueness is terribly overrated. We’re only as unique as every other species, each uniquely evolved to extract the best possible hope for our genes to be passed on into infinity given the present unique circumstances. With all the bones of evolution, and a modern understanding of evolution and genetics, it’s impossible to conceive of a twenty-step progress of apes from the left to the right, let alone those neat discrete jumps in five moves. There is no measure of the progress of evolution, and the language we once used, where species were “higher” or “lower,” no longer carries any meaning for science.

  Charles Darwin used those words,* as was the style of his time, when he outlined the mechanism for the origin of species in 1859. We had scant evidence for other upright apes then, with or without their spears. He had no mechanism for how that modification was passed from generation to generation. Since the end of the nineteenth century we’ve known the patterns by which characteristics are passed from parent to child. In the 1940s we discovered that DNA was the molecule that transmitted that information down the generations. Since 1953, we’ve known that the double helix is how DNA is built, giving it the impressive ability to copy itself and allow those copies to build cells just like the ones they came from. And since the 1960s we’ve known how DNA encodes proteins, and that all life is built of, or by, proteins. Those titans of science, Gregor Mendel, Francis Crick, James Watson, Rosalind Franklin, and Maurice Wilkins, stood on their predecessors’ and colleagues’ shoulders, and would in turn be the giants from whose shoulders all biologists would see into the future. The unraveling of these mysteries was the great science story of the twentieth century, and by the beginning of the twenty-first the principles of biology were set in place. In cracking the universal genetic code, and unwinding the double helix, we had unveiled a set of simple rules of life. Yet they turned out to be profoundly complex, as we will soon see.

  But Darwin didn’t know any of that. When he published his second great work, The Descent of Man, in 1871, his primary concern was the question of

  whether man, like every other species, is descended from some pre-existing form . . .

  Then, just a handful of Neanderthal remains were known: a skull from Belgium, another from Gibraltar, and a bag of bones from central Germany. As early as 1837, Darwin had sketched out a visionary version of an evolutionary tree in a notebook, showing how one branch of life became two and more, selected by nature in response to the changing environment. How these ancient apes fitted onto the human tree was entirely unknown.

  “I think,” he scrawled at the top of the page in that notebook, in his inimitably dreadful handwriting, but never finished that thought. What was set in motion in the nineteenth century was the idea that, alongside all animals, we were part of a continuum—a species begotten not created. Nowadays, only the willfully ignorant dismiss the truth that we evolved from earlier ancestors. The images of gigglemug skulls of our long-dead forebears are commonplace, and they become front-page news when a new species is claimed. Dozens of lines of evidence bellow incontrovertibly that we are an ape, with an ape ancestor common to chimpanzees, bonobos, gorillas, and orangutans.

  Sometimes people say, as a way of revealing the paucity of the fossil record, that all the specimens of ancient human evolution could be placed on a large table or in a single coffin. That’s not true either. We have literally thousands of ancient, hardened bones, found all around the world; many in the nursery of the human story in eastern Africa, many in Europe, and the more we look, the more we find. For Darwin, though, we were effectively alone at the end of a mysterious branch on our family tree.

  But for all the sheer grit of the diggers who devote their lives to sitting in dugout caves or dusty ancient riverbeds armed with toothbrushes and tiny pi
cks, there are not nearly enough physical specimens to reveal anything resembling a complete picture when it comes to human evolution; there are individual fossils arranged into groups according to shared characteristics such as the shapes of their brows, the arch of an instep, the cusps on their molars. These were dated according to where they were found, in which layer in the ground, and what other things are found nearby—tools, the shadows of cooking, or traces of hunting.

  Or if they’re young enough, by the ratio of radioactive carbon atoms that, instead of being replenished via living metabolism, in death are slowly ticking down at a regular rate. It’s all good, robust science, contentious as research often is, and frequently fractious, but the analysis of old bones is precise, complex, and highly sophisticated. In the 200 years since the first other human species was discovered, our understanding of how we came to be has undoubtedly increased immeasurably, but our confidence in that path has changed, and continues to evolve. For decades that image of the progress of monkey-ape to ape-man to man-ape has been on display in museums around the world, and in textbooks, a nice line of clear evolution that says “this is how we got here.” In Down House, in the English county of Kent, where Darwin beetled away, meticulously drawing up the best idea anyone ever had, you can still buy coffee mugs with that image on it.

  When I was young and falling in love with science in the 1980s, the evolutionary trees looked just like that. My father would collect articles for me from New Scientist or Scientific American showing neat branching diagrams suggesting that one species morphed into another, or one becoming two, with the other gruff ape-men perishing along the way. The picture seemed clearer, the fewer specimens we had. By the end of the twentieth century, more and more human species and specimens had risen from their graves, different enough to blur those nice clean lines, and the branches got fatter, less distinct and more pollarded.