Scatter, Adapt, and Remember: How Humans Will Survive a Mass Extinction

by Newitz, Annalee

  Besides, how likely is it that a group of H. sapiens nomads would attack a community of Neanderthals? These were explorers, after all, probably carrying their lives on their backs. Neanderthals may not have had a lot of tools, but they did have deadly spears they used to bring down mammoths. They had fire. Even with H. sapiens’ greater numbers, would these interlopers have had the resources to mount a civilization-erasing attack? Rather than starting a resource-intensive war against their neighbors, many H. sapiens could have opted to trade with the odd-looking locals, and eventually move in next to them. Over time, through trade (and, yes, the occasional battle) the two groups would have shared so much culturally and genetically that it would become impossible to tell them apart.

  This is precisely the kind of thinking that animates what’s called the multiregional theory of human development. Popularized by Wolpoff and his colleague John Hawks, this theory fits with the same archaeological evidence that supports the African replacement theory—it’s just a very different interpretation.

  Wolpoff’s idea hinges on the notion that the ancestors of Neanderthals and H. sapiens didn’t leave Africa as distinct groups, never to see each other again until the fateful meeting that Klein described with such horror. Instead, Wolpoff suggests, humans leaving Africa 1.8 million years ago forged a pathway that many other archaic humans walked—in both directions. Instead of embarking on several distinct migrations off the continent, humans expanded their territories little by little, essentially moving next door to their old communities rather than trekking thousands of kilometers to new homes. Indeed, the very notion of an “out of Africa” migration is based on an artificial political boundary between Africa and Asia, which would have been meaningless to our ancestors. They expanded to fill the tropical forests they loved, which happened to stretch across Africa and Asia during many periods in human evolution. Early humans would have been drifting back and forth between Africa, Asia, and Europe for hundreds of thousands of years. It was all just forest to Neanderthals and H. sapiens.

  If scientists like Wolpoff are right—and Hawks has presented compelling genetic evidence to back them up—then H. sapiens probably didn’t march out of Africa all at once and crush all the other humans. Instead, they evolved all over the world through an extended kinship network that may have included Neanderthals as well as other early humans like Denisovans and H. erectus.

  It’s important to understand that the multiregional theory does not suggest that two or three separate human lineages evolved in parallel, leading to present-day racial groups. That’s a common misinterpretation. Multiregionalism describes a human migration scenario similar to those we’re familiar with among humans today, where people cross back and forth between regions all the time. For multiregionalists, there were never two distinct waves of immigration, with one leading to Neanderthals, and the other packed with H. sapiens hundreds of thousands of years later. Instead, the migration (and evolution) of H. sapiens started 1.8 million years ago and never stopped.

  Many anthropologists believe that the truth lies somewhere in between African replacement and multiregionalism. Perhaps there were a few distinct waves of migration, such anthropologists will concede, but H. sapiens didn’t “replace” the Neanderthals. Instead, H. sapiens bands probably assimilated their unusual cousins through the early human version of intermarriage.

  Perhaps, when Neanderthals stood in the smooth stone entries to their caves and watched H. sapiens first entering their wooded valleys, they saw opportunity rather than a confusing threat. In this version of events, our ancient human siblings may have had few resources and lived a hardscrabble life, but they were H. sapiens’ mental equals. They exchanged ideas with the newcomers, developed ways of communicating, and raised families together. Their hybrid children deeply affected the future of our species, with a few of the most successful Neanderthal genes drifting outward into some of the H. sapiens population. Neanderthals went extinct, but their hybrid children survived by joining us.

  Whether you believe that humans exterminated or assimilated Neanderthals depends a lot on what you believe about your own species. Klein doesn’t think Neanderthals were inferior humans doomed to die—he simply believes that early H. sapiens would have been more likely to kill and rape their way across Europe in a Neanderthal holocaust, rather than making alliances with the locals. As his comment about the sexual predilections of modern men makes clear, Klein is basing his theory on what he’s observed of H. sapiens in the contemporary world. Tattersall amplified Klein’s comments by saying that he thinks humans 40,000 years ago probably treated Neanderthals the way we treat each other today. “Today, Homo sapiens is the biggest threat to its own survival. And [the Neanderthal extinction] fits that picture,” he said. Ultimately, Tattersall believes that we wiped out the Neanderthals just the way we’re wiping ourselves out today.

  Hawks, on the other hand, described a more complicated relationship between H. sapiens and Neanderthals. He believes that Neanderthals had the capacity to develop culture, but simply didn’t have the resources. “They made it in a world where very few of us would make it,” he said, referring to the incredible cold and food scarcity in the regions Neanderthals called home. Anthropologists, according to Hawks, often ask the wrong questions of our extinct siblings: “Why didn’t you invent a bow and arrow? Why didn’t you build houses? Why didn’t you do it like we would?” He thinks the answer isn’t that the Neanderthals couldn’t but that they didn’t have the same ability to share ideas between groups the way H. sapiens did. Their bands were so spread out and remote that they didn’t have a chance to share information and adapt their tools to life in new environments. “They were different, but that doesn’t mean there was a gulf between us,” Hawks concluded. “They did things working with constraints that people today have trouble understanding.” Put another way, Neanderthals spent all day in often fatal battles to get enough food for their kids to eat. As a result, they didn’t have the energy to invent bows and arrows in the evening. Despite these limitations, they formed their small communities, hunted collectively, cared for each other, and honored their dead.

  When H. sapiens arrived, Neanderthals finally had access to the kind of symbolic communication and technological adaptations they’d never been able to develop before. Ample archaeological evidence shows that they quickly learned the skills H. sapiens had brought with them, and started using them to adapt to a world they shared with many other groups who exchanged ideas on a regular basis. Instead of being driven into extinction, they enjoyed the wealth of H. sapiens’ culture and underwent a cultural explosion of their own. To put it another way, H. sapiens assimilated the Neanderthals. This process was no doubt partly coercive, the way assimilation so often is today.

  More evidence for Hawks’s claims comes from Neanderthal DNA. Samples of their genetic material can reveal just what happened after all that Pleistocene hanky-panky. A group of geneticists at the Max Planck Institute, led by Svante Pääbo, sequenced the genomes of a few Neanderthals who had died less than 38,000 years ago. After isolating a few genetic sequences that appear unique to Neanderthals, they found evidence that a subset of these sequences entered the H. sapiens genome after the first contact between the two peoples. Though this evidence does not prove definitively that genes flowed from Neanderthals into modern humans, it’s a strong argument for an assimilationist scenario rather than extermination.

  A big question for anthropologists has been whether H. sapiens comes from a “pure” lineage that springs from a single line of hominins like Mitochondrial Eve. The more the genetic evidence piles up, however, the more likely it seems that our lineage is a patchwork quilt of many peoples and cultures who intermingled as they spread across the globe. Present-day humans are the offspring of people who survived grueling immigrations, harsh climates, and Earth-shattering disasters.

  Most anthropologists are comfortable admitting that we just don’t know what happened when early humans left Africa, and are used to revising
their theories when new evidence presents itself. Klein’s influential textbook The Human Career is full of caveats about how many of these theories are under constant debate and revision. In 2011, for example, the anthropologist Simon Armitage published a paper suggesting that H. sapiens emerged from Africa as early as 200,000 years ago, settling in the Middle East. This flies in the face of previous theories, which hold that H. sapiens didn’t leave Africa until about 70,000 years ago. The story of how our ancestors emerged from their birthplaces in Africa turns out to be as complicated as a soap opera—and it likely includes just as much sex and death, too.

  Who Survived to Tell the Tale?

  Whether humans destroyed Neanderthals or merged with them, we’re left with a basic fact of anthropological history, which is that modern humans survived and Neanderthals did not. It’s possible that members of H. sapiens were better survivors than their hominin siblings because Neanderthals didn’t exchange symbolic information; they were too sparse, spread out, and impoverished to achieve a cultural critical mass the way their African counterparts did. But it seems that Neanderthals were still swept up into H. sapiens’ way of life in the end. Our Neanderthal siblings survive in modern human DNA because they formed intimate bonds with their new human neighbors.

  Svante Pääbo, who led the Neanderthal DNA sequencing project, recently announced a new discovery that also sheds light on why H. sapiens might have been a better survivor than H. neanderthalensis. After analyzing a newly sequenced genome from a Denisovan, a hominin more closely related to Neanderthals than H. sapiens are, Pääbo’s team concluded that there were a few distinct regions of DNA that H. sapiens did not share with either Neanderthals or Denisovans. Several of those regions contain genes connected to the neurological connections that humans can form in their brains. In other words, it’s possible that H. sapiens’ greater capacity for symbolic thought is connected to unique strands of DNA that the Neanderthals didn’t have.

  “It makes a lot of sense to speculate that what had happened is about connectivity in the brain, because … Neanderthals had just as large brains as modern humans had,” Pääbo said at a press conference in 2012 after announcing his discovery. “Relative to body size, they had even a bit larger brains [than H. sapiens]. Yet there is something special that happens with modern humans. It’s sort of this extremely rapid technological cultural development and large societal systems, and so on.” In other words, H. sapiens’ brains were wired slightly differently than their fellow hominins. And once Neanderthals merged with H. sapiens’ communities, bearing children with the new arrivals, their mixed offspring may have had brains that were wired differently, too. Looked at in this light, it’s as if H. sapiens assimilated Neanderthals both biologically and culturally into an idea-sharing tradition that facilitated rapid adaptation even to extremely harsh conditions.

  Early humans evolved brains that helped us spread ideas to our compatriots even as we scattered to live among new families and communities. It’s possible that this connectedness—both neurological and social—is what allowed groups of H. sapiens to assimilate their siblings, the Neanderthals. Still, our storytelling abilities are also what allow us to remember these distant, strange ancestors today.

  Humans’ greatest strength 30,000 years ago may have been an uncanny ability to assimilate other cultures. But in more recent human history, this kind of connectedness almost did us in. Once human culture scaled up to incorporate unprecedentedly enormous populations, our appetite for assimilation spread plagues throughout the modern world, almost destroying humanity many times over. And it spawned deadly famines, too. As we’ll see in the next two chapters, humanity’s old community-building habits can become pathological on a mass scale. Thousands of years after the merging of Neanderthals and H. sapiens, the practices that helped us survive in pre–ice age Europe became, in some contexts, liabilities. They wiped out whole civilizations and made it necessary for us to change the structures of human community forever.

  8. GREAT PLAGUES

  [Death] hath a thousand slayn this pestilence.

  And, maister, er ye come in his presence,

  Me thinketh that it were necessarie

  For to be war of switch an adversarie.

  Beth redy for to meete hym everemoore.

  —Geoffrey Chaucer, “The Pardoner’s

  Tale,” The Canterbury Tales, 1380s

  MOST PEOPLE KNOW British poet Geoffrey Chaucer because he wrote one of the earliest works of literature in English, The Canterbury Tales. What you may not know is that Chaucer came of age in a postapocalyptic world. Born in the 1340s, Chaucer would have been a little boy when the Black Death first struck England, in 1348; in the next few years it wiped out over 60 percent of the population of the British Isles. The son of a wealthy wine merchant, Chaucer grew up in London, already a bustling city where traders arriving in ships from Europe would have brought news of the “pestilence” ripping through the continent. The late 1340s marked the first great pandemic of what would later be called the bubonic plague, and the death tolls were so high that most bodies were thrown into mass graves because churchyards were overflowing. Even if there had been room for the corpses, it’s likely there were not enough clergy left to coordinate burials. Chaucer came of age in the wake of a pandemic so deadly that half the population of London perished.

  We hear of the Black Death only rarely in Chaucer’s considerable body of work, most memorably in the lines I’ve quoted above from The Canterbury Tales. The corrupt Pardoner is telling his fellow travelers a tale of three angry drunks who decide to kill Death, to avenge their friend’s murder. Violently intoxicated, they demand that a little boy carrying corpses to the graveyard tell them where to find “Deeth.” The boy warns them that Death “hath a thousand slayne this pestilence,” or slain a thousand people during the last bout of plague. The boy adds that they should be ready to meet Death “everemoore,” anytime. This casual reference to “pestilence,” written over 40 years after the plague first shattered England, indicates how ordinary the specter of mass death had become for people of Chaucer’s generation. The disease had returned again and again to claim thousands of lives during the late fourteenth century, though not with the ferocity that it had in Chaucer’s boyhood. The pestilence may not have touched the poet’s writings much, but its social reverberations marked his life and those of all his countrymen.

  Plague was a symptom of the problems humans had adapting to our own growing societies. By the time the Middle Ages rolled around, we were old pros at the symbolic-culture game that helped us outlast the Neanderthals, but we still had little experience with using that symbolic culture to unite large societies made up of many disparate groups. Humans first began experimenting with such societies during classical antiquity, in sprawling ancient empires like those of the Assyrians, the Romans, the Han, and the Inca. But these civilizations were exceptions rather than the norm for most people. During Chaucer’s lifetime in the Middle Ages, however, humanity began laying the foundations for what would over the next five centuries grow into modern, global society. And this transformation meant that for the first time, the greatest threat to humanity came not from nature, but from ourselves.

  A Revolutionary Pestilence

  In a country whose population was only 40 percent of what it had been in the years before his birth, Chaucer grew up with opportunities he might never have had otherwise. A man of lively intelligence, he got an uncommonly good education working as an esquire at the court of Edward III, a typical role for the child of a wealthy merchant. He managed to get good legal training by studying with attorneys who worked in the court’s “Inner Temple,” essentially a medieval law school. And then he found paying work as a representative for various members of the royal family, conducting business for them abroad (where he learned French and Italian) and eventually in London. Because Chaucer did so much business for the crown, he left a surprisingly detailed paper trail, including travel authorizations, expense accounts, promises of payment
, and legal documents. Scholars have pieced together his life from these scraps of paper.

  We know from these records that for twelve years, the former esquire lived with his wife and children in Aldgate, one of the wealthiest neighborhoods of London. Chaucer’s home was a fine set of rooms right above a gate in the ancient defensive walls that surrounded the city. In typical feudal fashion, the mayor had granted the dwelling to Chaucer rent-free at roughly the same time that Edward III put the future poet in charge of managing export taxes on wool in London’s Custom House. Apparently, Chaucer was quite good at his job. He did valuable accounting for the kingdom during the day, and probably made his first efforts at writing poetry during the evenings. Though Chaucer managed vast sums of money for the crown, he and his family were what would one day be called middle class. Connections to the royal family gave them just enough stature to merit a good living (his salary included a daily gallon pitcher of wine), and a nice home. One side effect of the Black Death was a dramatic reshuffling in the upper echelons of society, whose members had been thinned by the pestilence. Chaucer flitted from one good job to the next, always working closely with the crown, because there was a shortage of educated men who did not owe blood allegiance to one aristocratic family or another.