The Human Age: The World Shaped by Us

by Diane Ackerman

  Gene splicing and bioengineering would not appear for a hundred years, but Wells foresaw some of the ethical dilemmas they might pose a little later in the Anthropocene. Suppose, by accident or design, a subhuman chimera emerged, something more intelligent than other animals, but less so than humans? What purpose would it be expected to serve? What sort of home would it find in our society? Would it be relegated to a lower caste? Under what circumstances should we consider a man-made chimera human? What inalienable rights would it possess?

  DNA’S SECRET DOORMEN

  Swinging gamely among the fire-hose vines at the Toronto Zoo, Budi isn’t a cyborg or man-made chimera, and no human has reknit his DNA. He’s just a frisky orangutan kid, an emissary from the wild. But we’re starting to regard his physical nature (and our own) in radically new ways that connect and redefine us. Only the knowledge and what we can do with it are new. The rest is ancient as the family tree we share.

  A YOUNG WOMAN with chestnut hair is seated in front of me in the cinema, slouched down, watching Stanley Kubrick’s 2001: A Space Odyssey. On the art-house screen, a vegetarian ape idly fingers the scattered bones of a fallen antelope. Slowly an idea begins to take shape. Picking up a bone, he raises it over his head and smashes it down on the rest of the skeleton, over and over, striking and shattering in an orgy of violence, while the vision of a tasty tapir flickers through his head and the pounding chords of Richard Strauss’s Thus Spake Zarathustra drive home the message: Man the Hunter is born. A day later, the ape man uses his weapon to kill the leader of a rival band of apes, while the Strauss soundtrack grows orgasmic with a new drama: the blow-by-blow chords of war. From there, Kubrick treats us to human evolution, artificial intelligence, alien life, and technological pageantry. Cascading into the spacefaring future, we find an astronaut vying with a sentient, mentally disturbed computer (which he subdues with a tool far subtler than an antelope bone). Reaching the apogee of his fate, he’s transfigured in a process that’s too advanced for us relative cavemen (in the cave of the movie theater, anyway) to distinguish from magic. As the credits roll like blankets of stars, rising houselights return us to Earth and a human saga and future that seem all the more epic.

  When the chestnut-haired woman gets up to leave, one strand of hair remains on the back of her seat. From that tiny sample, someone could peruse the DNA and know if it belonged to a human female or an Irish setter or a fox, and find clues to her identity: ethnic background, eye color, likelihood of developing various diseases, even her probable life span. One would assume that she has little in common with a mouse or a roundworm, and yet they have a similar number of genes. She’s intimately related to almost every creature that walks, crawls, slithers, or flies, even the ones she’d find icky. Especially those. She shares all but a drop of her genetic heritage with spineless organisms. But that drop really counts.

  Thanks to the Human Genome Project’s library of our roughly twenty-five thousand protein-coding genes, available via the Internet to anyone with a yen to peruse it, a micro-stalker could analyze the rungs of our redhead’s DNA, creeping up its spiral ladders, and discovering all sorts of juicy nuggets. Some of the micro-portrait he finds will be quite recent, because by hogging and restyling the environment we’ve altered plants, animals, single-celled organisms, and ourselves. Her DNA will show a panoply of revisions, indicative of our age, which we’ve either stage-managed or accidentally caused. Could the pollutants we use, and the wars we wage, really change our DNA and rewire the human species?

  She knows they can, because in her college curriculum, Anthropocene Studies, she’s read research linking exposure to jet fuel, dioxin, the pesticides DEET and permethrin, plastics, and hydrocarbon mixtures to cancer, and not just in the person who had contact with it but for several generations. She’s learned how the arsenic-polluted drinking water in the Ganges delta in Bangladesh can lead to skin cancer, as can workplace exposure to cadmium, mercury, lead, and other heavy metals. Although she was tempted to spend her junior year abroad in Beijing, she’s having second thoughts now that a peer-reviewed PLOS ONE study ties life in smog-ridden cities to thickening of the arteries and heightened risk of heart disease. What clinches it is this headline in Mail Online: “China starts televising the sunrise on giant TV screens because Beijing is so clouded in smog.” Below it, a video shows a scarlet sunrise on an LED billboard in Tiananmen Square, completely encased by thick gray air, as if the sun were on display in a museum. Several black silhouettes are walking past it on their way to work, some wearing masks. As a daily jogger, she’d be inhaling a lot more pollution than most people, and she figures her genes have already been restyled just by growing up among the master trailblazers of the Human Age.

  But she is tempted to read the book of her genes, and discover more about her lineage and genetic biases. For a truly personal profile, all our redhead would need is a vial of her blood and between $100 and $1,000. Such companies as Navigenics or 23andMe will gladly provide a glimpse of her future, a tale still being written but legible enough for genetic fortune-telling. She may have a slightly higher than normal risk of macular degeneration, a tendency to go bald, a gene variant that’s a well-known cause of blood cancer, maybe a different variant associated with Alzheimer’s, the family bane. If she read the report herself, she might not handle that information well. It could kindle needless worry about ailments that will never materialize, or it might warn of an impending but treatable illness, or predict a serious, disabling disease like Huntington’s. As a supposed calmative, such tests are usually marketed as a “recreational” exercise, to discover if you’re part Cherokee or African or Celt, or Neanderthal, or even related to Genghis Khan, as I may well be.

  My mother always said I must be part Mongolian, because of my lotus-pale complexion and squid-ink-black hair. Something you’re not telling me? I was tempted to ask. But I knew she’d visited Mongolia with my father long after I was born. What I didn’t know is that one out of every two hundred males on Earth is related to Genghis Khan.

  An international team of geneticists conducting a ten-year study of men living in what once was the Mongolian empire discovered that a surprisingly large number share the identical Y chromosome, which is passed down only from father to son. One individual’s Y chromosome can be found in sixteen million men “in a vast section of Asia from Manchuria near the sea of Japan to Uzbekistan and Afghanistan in Central Asia.”

  The likeliest candidate is Khan, a warlord who raped and pillaged one town after another, killing all the men and impregnating the women, sowing his seed from China to Eastern Europe. Though legend credits Khan with many wives and offspring, he didn’t need to do all the begetting himself to ensure that his genes would flourish. His sons inherited the identical Y chromosome from him, as did their sons and their sons’ sons down a long, winding Silk Road of legitimate and illegitimate progeny. His equally warlike oldest son, Tushi, had forty legitimate sons (and who knows how many misbegotten), and his grandson Kublai Khan, who figured so large in Marco Polo’s life, had twenty-two.

  Their genes scattered exponentially in an ever-widening fan, and the process really picked up speed in the twentieth century, when cars, trains, and airplanes began propelling genes around the planet and stretching the idea of “courting distance,” which used to be only twelve miles—how far a man could ride on horseback to visit his sweetheart and return home the same day. Now it’s commonplace to have children with someone from thousands of miles, even half a world, away.

  Khan wasn’t trying to create a world in his image; his fiercest instincts had a mind of their own, and his savage personality spurred them on. Most people don’t run amok on murderous sprees, thank heavens, but history is awash with Khan-like wars and mayhem. In their wake, gene pools often change. One can only surmise that wiping out the genes of others and planting your own (what we call genocide) must come naturally to our kind, as it does to some other animals, from ants to lions.

  Typically, wandering male lions attack
a pride, drive off the other males, and kill their offspring. Then they mate with the females, ensuring that only the invaders’ genes will flourish. A colony of ants will slaughter millions of neighbors, provided they’re not family (somehow they can spot or whiff geographically distant kin they haven’t met before). Human history is riddled with similar dramas, but that doesn’t justify them. They were, and are, war’s legacy, an unconscious motive, not a blueprint for action.

  Except once. During World War II, Hitler and his henchmen devised an agenda, both political and genetic, that was nothing less than the Nazification of nature. The human cost is well known: the extermination of millions while, in baby farms scattered around Europe, robust SS men and blond, blue-eyed women produced thousands of babies to use as seed stock for Hitler’s new master race. What’s little known is that their scheme for redesigning nature didn’t stop with people. The best soldiers needed to eat the best food, which Nazi biology argued could grow only from the purest of seeds. So, using eugenics, a method of breeding to emphasize specific traits, the Nazis hoped to invade the genetic spirals of evolution, seize control, and replace “unfit” foreign crops and livestock with genetically pure, so-called Aryan ones.

  To that end, they created an SS commando unit for botanical collection, which was ordered to raid the world’s botanical gardens and institutes and steal the best specimens. Starting with Poland, they planned on using slave labor to drain about a hundred thousand square miles of wetlands so that they could farm it with Aryan crops. Draining the marshes might well lower the water table and create a dust bowl, and it would certainly kill the habitat of wolves, geese, wild boar, and many other native species, but despoilers rarely see downstream from events.

  Elsewhere, the Nazis proposed planting forests of oak, birch, beech, yew, and pine to sweeten the climate so that it was more favorable for their own oats and wheat, and they spoke openly about reshaping the landscape to better suit Nazi ideals. That revision included people, railways, animals, and land alike, even the geometry of farm fields (no acute angles below 70°), and the alignment of trees and shrubs (only on north-south or east-west axes). Today, though we deplore genocide it stubbornly persists, and we may have our work cut out for us because it seems to tap a deeply rooted drive. It’s bone-chilling how close the Nazis came to a feat of genetic domination that dwarfs all of Genghis Khan’s exploits.

  The human DNA that Olivine finds in future days will show some lineages, like Khan’s, triumphing through war, and others succeeding because of geography, religion, politics, fashionable ideals of beauty, and elements native to our age such as giant factories and workplaces, cars, jet travel, Internet and social media, the jammed crossroads of megacities, and widely available birth control and infertility treatments.

  When my mother teased about my being part Mongolian, she may have been right, since Genghis Khan and his clan reached into Russia. But I like knowing that the farther back one traces any lineage the narrower the path grows, to the haunt of just a few shaggy ancestors, with luck on their side, little gizmos in their cells, and a future storied with impulses and choices that will ultimately define them.

  The noble goal of the Human Genome Project is to use such knowledge to find new ways to understand, treat, and cure illness. In that sense, it’s a group portrait of us as a species, realized at last, a mere fifty years after Crick, Watson, and Franklin decoded the double-helix design of DNA. The only thing more unlikely than DNA itself, nature’s blueprint for building a human being, is our ability to decode it. Thus far, it’s our greatest voyage of discovery, and we’re still scouting its spiral coves.

  IN NORRBOTTEN, THE northernmost province of Sweden, the reindeer outnumber humans, and shimmery green veils of northern lights spiral up from the horizon like enchanted scarves. In summer, crops ripen under a ceramic sun; moon-shadows haunt the ice-marbled winter nights. Although the citizens can travel by car today, in the past they relied on foot or horse power to carry them to grace at an early-fifteenth-century church in the ancient settlement of Gammelstad, where they eased their isolation and replenished hope.

  Getting there was only half the pilgrimage. Needing rest before the formidable trek home, each family retired to their tiny wooden house near the church, painted red with windows and doors picked out in white. Some bore grass roofs. Delicate lace curtains hemmed the frost-curled windows, and stout shutters sealed out the warring tempests. Doors were adorned with a pyramid motif, a legacy from pagan antiquity admired for its stark symmetry, and reinterpreted as a Christian altar lit by sacrificial fire.

  In such a remote frontier, the human population thinned to only about six people per square mile, and farmers crafted what they needed, from harnesses to nails. Neighbors helped neighbors, and married neighbors. But if the harvest failed—as it did with alarming frequency—rescue lay too far away. Railways didn’t venture that far north, even at the height of the Industrial Age when iron horses snorted soot across many frontiers, and in any case locals spoke a dialect unintelligible to other Swedes.

  Gammelstad’s church, plus the rows of red bungalows clustered behind it, are part of a World Heritage Site that also includes the remains of a six-thousand-year-old Stone Age settlement in the heart of town. Tourists are today’s pilgrims, closely followed by geneticists. It’s an unlikely setting to be at the center of a revolution in medicine, and yet it holds an important key to the health and longevity of everyone on Earth.

  In the nineteenth century, Norrbotten’s fickle climate bred many lopsided years of surfeit or famine, with no way to foretell the fate of the crops. People either nearly starved or died. For example, 1800, 1812, 1821, 1836, and 1856 all were years of deprivation, when crops totally failed (including staples like potatoes and grains for porridge), farm animals died, families suffered pounding hunger and malnutrition, and underweight babies entered a lean world with even leaner prospects. But in 1801, 1822, 1828, 1844, and 1863, on the other hand, the weather sweetened and food leapt from the soil in such abundance that families thrived, the economy bloomed, and for many people overeating became a pastime.

  If we jump to the 1980s and step across the North Sea to London, we find the prestigious medical journal The Lancet publishing studies that highlighted the importance of womb-time, linking a mother’s poor diet during pregnancy with her child’s higher risk of heart disease, diabetes, obesity, and related illnesses. This was a revelation to the medical community and a warning to parents.

  According to Darwin’s theory of natural selection, a child is born with a genetic blueprint that has evolved over millennia. All the hard-luck times its parents faced might be taught as life lessons, but they aren’t hereditary; they won’t alter a child’s chemistry. Thinking otherwise was a delusion mocked and dismissed in the eighteenth century, when the naturalist Jean-Baptiste Lamarck (the man who coined the word “biology”) posed a theory that parents could pass along acquired traits to their offspring. In his most famous example, a giraffe reaches achingly high into the treetops each day to feed on tasty leaves, which ultimately lengthens its neck, and then its offspring inherit longer necks and stretch them even more by mimicking the parent’s behavior. Smart, keen-eyed, and right about many aspects of botany and zoology, including the dangerous idea that new species arise naturally through evolution, Lamarck was wrongheaded about giraffe necks and heritable traits. According to his logic, if a blacksmith grew anvil-hard arms from a lifetime of heavy hammering, his offspring would inherit equally burly muscles. It’s fun to think what such a world would look like—a mismatched crowd of animals within each species and the enviable ability to will traits to one’s offspring. Practice wouldn’t be needed—you could inherit your pianist dad’s spiderlike dexterity with his fingers or your bicycling mom’s loaflike quadriceps.

  Darwinian evolution teaches us that genetic changes in DNA unfold with granular slowness over millennia; no individual can erase or rewrite them in his lifetime. Genetic mutations come and go, and if one is harmful or useles
s for survival, it tends not to linger. But if it’s beneficial it equips the animal with an edge, a better chance at surviving long enough to breed, and then the mutation empowers the animal’s offspring and their offspring in turn, passing the winning trait along to future generations in quite a sloppy way, all things considered. In time this fluky mechanism leaves the world with only those animals best suited to their different habitats.

  That’s the accepted theory, proven in countless experiments, and there’s no reason to doubt it. But what if that isn’t the whole story? Eclipsed by Darwin, Lamarck seems to have been right at least in spirit, a reality that has stunned much of the scientific world. What makes a paradigm shift so shifty is that you don’t see it coming. Then it suddenly pulls a mental ripcord and your mind plummets at speed. A new paradigm blossoms overhead, the freefall slows to float, and the world becomes visible once again, but from a new perspective. “Creative insight,” we call this parachute flare with discovery.

  After Lars Olov Bygren, of the Karolinska Institute in Stockholm, read the Lancet articles, he began to wonder about the nineteenth-century children of Norrbotten who had alternately starved and binged. The people of that region seemed ideally isolated for a genetics study. Certainly the children would have been influenced by their mothers’ nutrition during pregnancy, but what about all the earlier feasts and famines their parents endured—could those blemish the children’s health? This was a daring question to ask, let alone pursue, since it flew in the face of Darwinian fashion. But it nagged at him until he finally decided to focus on ninety-nine children born in Överkalix in 1905, relying on a wealth of historical data. Why choose those mountain bluffs and chanting shores?