by Sam Kean
What Guy needs is a Doll with the same two fused chromosomes. Now, the odds of two people with the same fusion meeting and having children might seem infinitesimal. And they would be—except in inbred families. Relatives share enough genes that, given one person with a fusion, the chances of finding a cousin or half sibling with the same fusion don’t round down to zero so easily. What’s more, while the odds of Guy and Doll having a healthy child remain low, every thirty-sixth spin of the genetic roulette wheel (because 1/6 x 1/6 = 1/36), the child would inherit both fused chromosomes, giving him forty-six total. And here’s the payoff: Junior and his forty-six chromosomes would have a much easier time having children. Remember that the fusion itself doesn’t disable or ruin a chromosome’s DNA; lots of healthy people worldwide have fusions. It’s only reproduction that gets tricky, since fusions can lead to an excess or deficit of DNA in embryos. But because he has an even number of chromosomes, little Junior wouldn’t have any unbalanced sperm cells: each would have exactly the right amount of DNA to run a human, just packaged differently. As a result, all his children would be healthy. And if his children start having their own children—especially with other relatives who have forty-six or forty-seven chromosomes—the fusion could start to spread.
Scientists know this scenario isn’t just hypothetical, either. In 2010 a doctor in rural China discovered a family with a history of consanguineous (similar-blood) marriages. And among the various overlapping branches of the family tree, he discovered a male who had forty-four chromosomes. In this family’s case, the fourteenth and fifteenth chromosomes had fused, and consistent with the example of Guy and Doll, they had a brutal record of miscarriages and spontaneous abortions in their past. But from that wreckage, a perfectly healthy man with two fewer chromosomes emerged—the first known stable reduction since our ancestors started down the path to forty-six chromosomes a million years ago.*
In one sense, then, Theophilus Painter was right: for most of our primate history, the human line did have the same number of chromosomes as many primates. And until that transition, the hybrids that Ivanov coveted were far more possible. Having a different number of chromosomes won’t always prevent breeding; horses have sixty-four chromosomes, and donkeys sixty-two. But again, molecular gears and cogs don’t turn nearly as smoothly when chromosomes don’t correspond. Indeed, it’s telling that Painter published his study in 1923, just before Ivanov started his experiments. Had Painter guessed forty-six instead of forty-eight, that might have been a serious blow to Ivanov’s hopes.
And perhaps not just Ivanov’s. The issue remains disputed, and most historians dismiss the story as legend, if not outright legerdemain. But according to documents that a Russian historian of science unearthed in Soviet archives, Joseph Stalin himself approved the funding for Ivanov’s work. This is strange, since Stalin abhorred genetics: he later allowed his scientific hatchet man Trofim Lysenko to outlaw Mendelian genetics in the Soviet Union, and, poisoned by Lysenko’s influence, angrily rejected Hermann Muller’s eugenics program to breed better Soviet citizens. (Muller fled in response, and colleagues he left behind were shot as “enemies of the people.”) And that discrepancy—supporting Ivanov’s indecent proposals, yet rejecting Muller’s so vehemently—has led a few Russian historians to suggest (and here’s the dubious bit) that Stalin dreamed of using Ivanov’s humanzees as slaves. The legend really took off in 2005 when, through a series of convoluted attributions, the Scotsman newspaper in Great Britain quoted unnamed Moscow newspapers quoting still more recovered documents that themselves supposedly quoted Stalin as saying: “I want a new invincible human being, insensitive to pain, resistant and indifferent about the quality of food they eat.” On the same day, the Sun tabloid also quoted Stalin as saying he thought it best if humanzees have “immense strength but… an underdeveloped brain,” presumably so they wouldn’t revolt or be miserable enough to kill themselves. Apparently Stalin coveted the beasts to build his Trans-Siberian Railway through Gulag-land, one of history’s all-time biggest boondoggles, but his primary goal was repopulating the Red Army, which in World War I (as in most Russian wars) had suffered massive losses.
It’s a fact that Stalin approved funding for Ivanov. But not much, and he approved funding for hundreds of other scientists as well. And I’ve seen no firm evidence—or any evidence, really—that Stalin lusted after a humanzee army. (Nor that he planned, as some suggest, to seek immortality by harvesting humanzee glands and transplanting them into himself and other top Kremlin officials.) Still, I have to admit it’s a hell of a lot of fun to speculate about this. If Stalin did take a creepy interest in Ivanov’s work, that might explain why Ivanov got funding just as Stalin consolidated his power and decided to rebuild the military. Or why Ivanov established the primate station in Georgia, Stalin’s homeland. Or why the secret police arrested Ivanov after his failures, and why Ivanov couldn’t pay surrogate mothers but had to find volunteers who would reproduce for the love of Mother Russia—because after nursing, they would turn their “sons” and “daughters” over to Papa Stalin anyway. The international counterfactuals are even more fascinating. Would Stalin have sent monkey battalions over the North Pole, to invade North America? Would Hitler still have signed the nonaggression pact if he’d known Stalin was polluting the Caucasian race like this?
Still, assuming Ivanov could even create humanzees, Papa’s purported military plans would probably have come to naught. If nothing else—and I’m ignoring the difficulty of training half chimps to drive tanks or shoot Kalashnikovs—the Soviet Union’s climate alone would probably have annihilated them. Ivanov’s primates suffered from being too far north on the palm-treed coast of Georgia, so it seems doubtful that even a hybrid would have survived Siberia or months of trench warfare.*
What Stalin really needed weren’t humanzees but Neanderthals—big, bad, hairy hominids adapted to icy weather. But of course Neanderthals had gone extinct tens of thousands of years before, for reasons that remain blurry. Some scientists once believed that we actively drove Neanderthals into extinction through war or genocide. That theory has fallen out of favor, and theories about competition over food or climate change have come to the fore. But in all likelihood, there was nothing inevitable about our survival and their death. In fact, for much of our evolution, we humans were probably as dainty and vulnerable as Ivanov’s primates: cold snaps, habitat loss, and natural disasters seem to have crashed our population numbers time and again. And far from this being distant history, we’re still dealing with the repercussions. Notice that we’ve once again explained one mystery of human DNA—how an inbred family might drop two chromosomes—only to raise another—how that new DNA became standard in all humans. It’s possible that the ancient twelve-thirteen fusion created fancy new genes, giving the family survival advantages. But probably not. A more plausible explanation is that we suffered a genetic bottleneck—that something wiped out everyone on earth except a few tribes, and that whatever genes those dumb-lucky survivors had spread far and wide. Some species get caught in bottlenecks and never escape—behold Neanderthals. As the scars in our DNA attest, we human beings scraped through some pretty narrow bottlenecks ourselves, and might easily have joined our thick-browed brethren in Darwin’s dustbin.
PART III
Genes and Geniuses
How Humans Became All Too Human
10
Scarlet A’s, C’s, G’s, and T’s
Why Did Humans Almost Go Extinct?
Crisp mice in golden batter. Panther chops. Rhino pie. Trunk of elephant. Crocodile for breakfast. Sliced porpoise head. Horse’s tongue. Kangaroo ham.
Yes, domestic life was a trifle off at William Buckland’s. Some of his Oxford houseguests best remembered the front hallway, lined like a catacomb with the grinning skulls of fossilized monsters. Others remembered the live monkeys swinging around, or the pet bear dressed in a mortarboard cap and academic robes, or the guinea pig nibbling on people’s toes beneath the dinner table (at least until
the family hyena crushed it one afternoon). Fellow naturalists from the 1800s remembered Buckland’s bawdy lectures on reptile sex (though not always fondly; the young Charles Darwin thought him a buffoon, and the London Times sniffed that Buckland needed to watch himself “in the presence of ladies”). And no Oxonian ever forgot the performance art stunt he pulled one spring when he wrote “G-U-A-N-O” on the lawn with bat feces, to advertise it as fertilizer. The word did indeed blaze green all summer.
But most people remembered William Buckland for his diet. A biblical geologist, Buckland held the story of Noah’s ark dear, and he ate his way through most of Noah’s litter, a habit he called “zoophagy.” Any flesh or fluid from any beast was eligible for ingestion, be it blood, skin, gristle, or worse. While touring a church once, Buckland startled a local vicar—who was showing off the miraculous “martyr’s blood” that dripped from the rafters every night—by dropping to the stone floor and dabbing the stain with his tongue. Between laps Buckland announced, “It’s bat urine.” Overall Buckland found few animals he couldn’t stomach: “The taste of mole was the most repulsive I knew,” he once mused. “Until I tasted a bluebottle [fly].”*
William Buckland ate his way through most of the animal kingdom. (Antoine Claudet)
Buckland may have hit upon zoophagy while collecting fossils in some remote pocket of Europe with limited dining options. It may have been a harebrained scheme to get inside the minds of the extinct animals whose bones he dug up. Mostly, though, he just liked barbecuing, and he kept up his hyper-carnivorous activities well into old age. But in one sense, the most amazing thing about Buckland’s diet wasn’t the variety. It was that Buckland’s intestines, arteries, and heart could digest so much flesh, period, and not harden over the decades into a nineteenth-century Body Worlds exhibit. Our primate cousins could never survive the same diet, not even close.
Monkeys and apes have molars and stomachs adapted to pulping plant matter, and eat mostly vegan diets in the wild. A few primates, like chimpanzees, do eat a few ounces of termites or other animals each day on average, and boy do they love tucking into small, defenseless mammals now and then. But for most monkeys and apes, a high-fat, high-cholesterol diet trashes their insides, and they deteriorate at sickening speeds compared to modern humans. Captive primates with regular access to meat (and dairy) often end up wheezing around inside their cages, their cholesterol pushing 300 and their arteries paved with lard. Our protohuman ancestors certainly also ate meat: they left too many stone cleavers lying next to piles of megamammal bones for it all to be coincidence. But for eons early humans probably suffered no less than monkeys for their love of flesh—Paleolithic Elvises wandering the savanna.
So what changed between then and now, between Grunk in ancient Africa and William Buckland at Oxford? Our DNA. Twice since we split off from chimps, the human apoE gene has mutated, giving us distinct versions. Overall it’s the strongest candidate around (though not the only candidate) for a human “meat-eating gene.” The first mutation boosted the performance of killer blood cells that attack microbes, like the deadly microbes lingering in mouthfuls of raw flesh. It also protected against chronic inflammation, the collateral tissue damage that occurs when microbial infections never quite clear up. Unfortunately this apoE probably mortgaged our long-term health for short-term gain: we could eat more meat, but it left our arteries looking like the insides of Crisco cans. Lucky for us, a second mutation appeared 220,000 years ago, which helped break nasty fats and cholesterol down and spared us from premature decrepitude. What’s more, by sweeping dietary toxins from the body, it kept cells fitter and made bones denser and tougher to break in middle age, further insurance against early death. So even though early humans ate a veritable Roman-orgy diet compared to their fruitarian cousins, apoE and other genes helped them live twice as long.
Before we congratulate ourselves, though, about getting our hands on better apoEs than monkeys, a few points. For starters, bones with hack marks and other archaeological evidence indicate that we started dining on meat eons before the cholesterol-fighting apoE appeared, at least 2.5 million years ago. So for millions of years we were either too dim to link eating meat and early retirement, too pathetic to get enough calories without meat, or too brutishly indulgent to stop sucking down food we knew would kill us. Even less flattering is what the germicidal properties of the earlier apoE mutation imply. Archaeologists have found sharpened wooden spears from 400,000 years ago, so some caveman studs were bringing home bacon by then. But what about before that? The lack of proper weapons, and the fact that apoE combats microbes—which thrive in shall we say less-than-fresh cuts of carrion—hint that protohumans scavenged carcasses and ate putrid leftovers. At best, we waited for other animals to fell game, then scared them off and stole it, hardly a gallant enterprise. (At least we’re in good company here. Scientists have been having the same debate for some time about Tyrannosaurus rex: Cretaceous alpha-killer, or loathsome poacher?)
Once again DNA humbles and muddies our view of ourselves. And apoE is just one of many cases where DNA research has transformed our knowledge of our ancient selves: filling in forgotten details in some narratives, overthrowing long-held beliefs in others, but always, always revealing how fraught hominid history has been.
To appreciate how much DNA can supplement, annotate, or plain rewrite ancient history, it helps to look back to the days when scholars first started digging up human remains and studying them—the beginnings of archaeology and paleontology. These scientists started off with confidence about human origins, were thrown into confusion by unsettling finds, and only recently flowed back toward (if not all the way to) clarity, thanks largely to genetics.
Except in unnatural cases, like Dutch sailors massacring dodos, virtually no scientist before 1800 believed that species went extinct. They had been created as is, and that was that. But a French naturalist named Jean-Léopold-Nicolas-Frédéric Cuvier upended this notion in 1796. Cuvier was a formidable man, half Darwin, half Machiavelli. He later latched onto Napoleon and rode the little dictator’s blue coattails to the pinnacle of European scientific power; by life’s end, he was Baron Cuvier. But along the way the baron proved himself one of the great naturalists ever (his power wasn’t undeserved), and he built an authoritative case that species could in fact vanish. The first clue came when he recognized that an ancient pachyderm, unearthed in a quarry near Paris, had no living descendants. Even more spectacularly, Cuvier disproved old legends about the so-called Homo diluvii testis skeleton. These bones, unearthed years before in Europe, resembled a deformed man with stunted limbs. Folklore had identified “him” as one of the lecherous and corrupted folk that God had expunged with Noah’s flood. The less credulous Cuvier correctly identified the skeleton as, of all things, a titanic salamander that had long ago disappeared from the earth.
Still, not everyone believed Cuvier about the impermanence of species. The keen amateur naturalist (and U.S. president) Thomas Jefferson instructed Lewis and Clark to keep their eyes peeled inside the Louisiana Territory for giant sloths and mastodons. Fossils of both creatures had previously turned up in North America, drawing huge crowds to dig sites. (Charles Willson Peale’s painting The Exhumation of the Mastodon captures the scene elegantly.) Jefferson wanted to track down living examples of these beasts for patriotic reasons: he was fed up with European naturalists who, without ever coming within an ocean of America, dismissed the fauna here as sickly, weak, and stunted, a snobby theory called “American degeneracy.” Jefferson wanted to prove American wildlife was as big and hairy and virile as European beasts, and underlying his hope that mastodons and giant sloths still roamed (or inched across) the Great Plains was the belief that species cannot go extinct.
The Exhumation of the Mastodon, by Charles Willson Peale, showing the discovery of mastodon bones in New York in 1801. U.S. president Thomas Jefferson argued that mastodons must still be lumbering across North America, and ordered Lewis and Clark to keep their eyes peeled. (MA5911
, courtesy of the Maryland Historical Society)
Although William Buckland came down more with the sober extinctionists than the excitable nonextinctionists, he contributed to the debate in his characteristically flamboyant way. For his honeymoon, Buckland dragged his wife specimen hunting across Europe; and even while hiking to remote outcroppings and pickaxing rocks for fossils, he insisted on wearing black academic robes and often a top hat. In addition to bones, Buckland grew obsessed with fossilized hunks of animal shit, called coprolites, which he generously donated to museums. But Buckland made discoveries exciting enough to be forgiven his eccentricities. In one case he excavated an ancient underground predators’ lair in Yorkshire, with plenty of snarly teeth and gnawed-on skulls to wow the public. But the work had great scientific merit and bolstered the extinctionist case: the predators were cave hyenas, and since those hyenas no longer lived in England, they must have gone extinct. More profoundly—and fitting, given his proclivity for meat—Buckland identified some vast bones exhumed from an English quarry as a new species of giant reptile, the first example of the most terrifying carnivores ever, dinosaurs. He named it Megalosaurus.*
However confident he was with extinct animals, Buckland wavered, even equivocated, on the more loaded question of whether ancient human lineages ever existed. Although an ordained minister, Buckland didn’t believe in the aleph-by-aleph accuracy of the Old Testament. He speculated that geological eras had existed before “In the Beginning,” eras populated with the likes of Megalosaurus. Nevertheless, like virtually all scientists, Buckland hesitated to contradict Genesis regarding human origins and our special, recent creation. In 1823, when Buckland unearthed the alluring Red Lady of Paviland—a skeleton covered with seashell jewelry and dusted with red ocher makeup—he ignored plenty of contextual evidence and identified her as a witch or prostitute from no earlier than Roman times. The lady was actually thirty thousand years old (and a man). Buckland also dismissed clear evidence at another site of chipped-flint tools appearing in the same soil layer as pre-Genesis beasts like mammoths and saber-toothed tigers.