by Dan Ariely
Several years ago, Pääbo and a colleague, Wolfgang Enard, became interested in a gene known as FOXP2, which in humans is associated with language. (People who have a faulty copy of the gene—an extremely rare occurrence—are capable of speech, but what they say is, to strangers, mostly incomprehensible.) Pääbo and Enard had some mice bred with a humanized version of the gene and then studied them from just about every possible angle. The altered mice, it turned out, squeaked at a lower pitch than their un-humanized peers. They also exhibited measurable differences in neural development. (While I was in Leipzig, I watched a graduate student cut the heads off some of the altered mice and then slice up their brains, like radishes.) The Neanderthals’ FOXP2 gene, it turns out, is in almost all ways identical to humans’, but there is one suggestive base-pair difference. When this difference was discovered, it prompted Pääbo to order up a new round of transgenic mice, which, at the time of my visit, had just been born and were being raised under sterile conditions in the basement.
Genes that seem to play a role in speech are obvious places to look for human-specific changes. But one of the main points of sequencing the Neanderthal genome is that the most obvious places to look may not be the right ones.
“The great advantage with genomics in this form is that it’s unbiased,” Pääbo told me. “If you go after candidate genes, you’re inherently saying what you think the most important thing is. Language, many people would say. But perhaps we will be surprised—perhaps it’s something else that was really crucial.” Recently, Pääbo has become interested in a gene known as RUNX2, which is involved in bone formation. When members of his team analyzed the human and Neanderthal genomes mathematically, RUNX2 emerged as a place where significant changes in the human lineage seem to have occurred. People who have faulty copies of the RUNX2 gene often develop a condition, known as cleidocranial dysplasia, whose symptoms include such Neanderthal-like features as a flared rib cage. Two genes that have been implicated in autism, CADPS2 and AUTS2, also appear to have changed substantially between Neanderthals and humans. This is interesting because one of the symptoms of autism is an inability to read social cues.
One afternoon, when I wandered into his office, Pääbo showed me a photograph of a skullcap that had recently been discovered by an amateur collector about half an hour from Leipzig. From the photograph, which had been e-mailed to him, Pääbo had decided that the skullcap could be quite ancient—from an early Neanderthal or even a Homo heidelbergensis. He’d also decided that he had to have it. The skullcap had been found at a quarry in a pool of water—perhaps, he theorized, these conditions had preserved it, so that if he got to it soon, he’d be able to extract some DNA. But the skull had already been promised to a professor of anthropology in Mainz. How could he persuade the professor to give him enough bone to test?
Pääbo called everyone he knew who he thought might know the professor. He had his secretary contact the professor’s secretary to get the professor’s private cell-phone number, and joked—or maybe only half joked—that he’d be willing to sleep with the professor if that would help. The frenzy of phoning back and forth across Germany lasted for more than an hour and a half, until Pääbo finally talked to one of the researchers in his own lab. The researcher had seen the actual skullcap and concluded that it probably wasn’t very old at all. Pääbo immediately lost interest in it.
With old bones, you never really know what you’re going to get. A few years ago, Pääbo managed to get hold of a bit of tooth from one of the so-called “hobbit” skeletons found on the island of Flores, in Indonesia. (The “hobbits,” who were discovered in 2004, are generally believed to have been diminutive archaic humans—Homo floresiensis—though some scientists have argued that they were just modern humans who suffered from microcephaly.) The tooth, which was about 17,000 years old, yielded no DNA.
Then, about a year and a half ago, Pääbo obtained a fragment of finger bone that had been unearthed in a cave in southern Siberia along with a weird, vaguely human-looking molar. The finger bone—about the size of a pencil eraser—was believed to be more than 40,000 years old. Pääbo assumed that it came either from a modern human or from a Neanderthal. If it proved to be the latter, then the site would be the farthest east that Neanderthal remains had been found.
In contrast to the hobbit tooth, the finger fragment yielded astonishingly large amounts of DNA. When the analysis of the first bits was completed, Pääbo happened to be in the United States. He called his office, and one of his colleagues said to him, “Are you sitting down?” The DNA showed that the digit could not have belonged to a Neanderthal or to a modern human. Instead, its owner must have been part of some entirely different and previously unsuspected type of hominid. In a paper published in December 2010 in Nature, Pääbo and his team dubbed this group the Denisovans, after the Denisova Cave, where the bone had been found. “Giving Accepted Prehistoric History the Finger,” ran the headline on the story in the Sydney Morning Herald. Amazingly—or perhaps, by now, predictably—modern humans must have interbred with Denisovans, too, because contemporary New Guineans carry up to 6 percent Denisovan DNA. (Why this is true of New Guineans but not native Siberians or Asians is unclear, but presumably has to do with patterns of human migration.)
It has been understood for a long time that modern humans and Neanderthals were contemporaries. The discovery of the hobbits and now the Denisovans shows that humans shared the planet with at least two additional creatures like ourselves. And it seems likely that as DNA from more ancient remains is analyzed, still other human relatives will be found; as Chris Stringer, a prominent British paleoanthropologist, told me, “I’m sure we’ve got more surprises to come.”
“If these other forms of humans had survived two thousand generations more, which is not so much, then how would that have influenced our view of the living world?” Pääbo said, once the excitement over the skullcap had passed and we were sitting over coffee. “We now make this very clear distinction between humans and animals. But it might not be as clear. That is sort of an interesting thing to philosophize about.” It’s also interesting to think about why we’re the ones who survived.
Over the decades, many theories have been offered to explain what caused the demise of the Neanderthals, ranging from climate change to simple bad luck. In recent years, though, it’s become increasingly clear that, as Pääbo put it to me, “their bad luck was us.” Again and again, the archaeological evidence in Europe indicates, once modern humans showed up in a region where Neanderthals were living, the Neanderthals in that region vanished. Perhaps the Neanderthals were actively pursued, or perhaps they were just outcompeted. The Neanderthals’ “bad luck” is presumably the same misfortune that the hobbits and the Denisovans encountered, and similar to the tragedy suffered by the giant marsupials that once browsed Australia, and the varied megafauna that used to inhabit North America, and the moas that lived in New Zealand. And it is precisely the same bad luck that has brought so many species—including every one of the great apes—to the edge of oblivion today.
“To me, the mystery is not the extinction of the Neanderthals,” Jean-Jacques Hublin, the director of the Institute for Evolutionary Anthropology’s department of human evolution, told me. “To me the mystery is what makes modern humans such a successful group that they have been replacing not just the Neanderthals but everything. We don’t have much evidence that the Neanderthals or other archaic humans ever led to an extinction of a species of mammal or anything else. For modern humans, there are hundreds of examples, and we do it very well.”
One of the largest assemblages of Neanderthal bones ever found—remains from seven individuals—was discovered about a century ago at a spot known as La Ferrassie, in southwestern France. La Ferrassie is in the Dordogne, not far from La Chapelle and within half an hour’s drive of dozens of other important archaeological sites, including the painted caves at Lascaux. Over the summer, a team that included one of Pääbo’s colleagues was excavating at La F
errassie, and I decided to go down and have a look. I arrived at the dig’s headquarters—a converted tobacco barn—just in time for a dinner of boeuf bourguignonne, which was served on makeshift tables in the backyard.
The next day, I drove out to La Ferrassie with some of the team’s archaeologists. The site lies in a sleepy rural area, right by the side of the road. Many thousands of years ago, La Ferrassie was a huge limestone cave, but one of the walls has since fallen in, and now it is open on two sides. A massive ledge of rock juts out about twenty feet off the ground, like half of a vaulted ceiling. The site is ringed by a wire fence and hung with tarps, which give it the aspect of a crime scene.
The day was hot and dusty. Half a dozen students crouched in a long trench, picking at the dirt with trowels. Along the side of the trench, I could see bits of bone sticking out from the reddish soil. The bones toward the bottom, I was told, had been tossed there by Neanderthals. The bones near the top were the leavings of modern humans, who occupied La Ferrassie once the Neanderthals were gone. The Neanderthal skeletons from the site had long since been removed, but there was still hope that some stray bit, like a tooth, might be found. Each bone fragment that was unearthed, along with every flake of flint and anything else that might even remotely be of interest, was set aside to be taken back to the headquarters to be sorted and tagged.
After watching the students chip away for a while, I retreated to the shade. I tried to imagine what life had been like for the Neanderthals at La Ferrassie. Though the area is now wooded, then it would have been tundra. There would have been elk roaming the valley, and reindeer and wild cattle and mammoths. Beyond these stray facts, not much came to me. I put the question to the archaeologists I had driven out with.
“It was cold,” Shannon McPherron, of the Max Planck Institute, volunteered.
“And smelly,” Dennis Sandgathe, of Canada’s Simon Fraser University, said.
“Probably hungry,” Harold Dibble, of the University of Pennsylvania, added.
“No one would have been very old,” Sandgathe said.
Later on, back at the barn, I picked through the bits and pieces that had been dug up over the past few days. There were hundreds of fragments of animal bone, each of which had been cleaned and numbered and placed in its own little plastic bag, and hundreds of flakes of flint. Most of the flakes were probably the detritus of toolmaking—the Stone Age equivalent of wood shavings—but some, I learned, were the tools themselves. Once I was shown what to look for, I could see the beveled edges that the Neanderthals had crafted. One tool in particular stood out: a palm-size flint shaped like a teardrop. In archaeological terms, it was a hand axe, though it probably was not used as an axe in the contemporary sense of the word. It had been found near the bottom of the trench, so it was estimated to be about 70,000 years old. I took it out of its plastic bag and turned it over. It was almost perfectly symmetrical and—to a human eye, at least—quite beautiful. I said that I thought the Neanderthal who had fashioned it must have had a keen sense of design. McPherron objected.
“We know the end of the story,” he told me. “We know what modern culture looks like, and so then what we do is we want to explain how we got here. And there’s a tendency to overinterpret the past by projecting the present onto it. So when you see a beautiful hand axe and you say, ‘Look at the craftsmanship on this; it’s virtually an object of art,’ that’s your perspective today. But you can’t assume what you’re trying to prove.”
Among the hundreds of thousands of Neanderthal artifacts that have been unearthed, almost none represent unambiguous attempts at art or adornment, and those that have been interpreted this way—for instance, ivory pendants discovered in a cave in central France—are the subject of endless, often abstruse disputes. (Many archaeologists believe that the pendants were created by Neanderthals who had come into contact with modern humans and were trying to imitate them, but, relying on the most recent dating techniques, some argue that the pendants were, in fact, created by modern humans.) This paucity has led some to propose that Neanderthals were not capable of art or—what amounts to much the same thing—not interested in it. They simply did not possess what, genomically speaking, might be called the aesthetic mutation.
On my last day in the Dordogne, I decided to visit a nearby human site known for its extraordinary images. The site, Grotte des Combarelles, is a long, very narrow cave that zigzags through a limestone cliff. Hundreds of feet in, the walls of the cave are covered with engravings—a mammoth curling its trunk, a wild horse lifting its head, a reindeer leaning forward, apparently to drink. In very recent times, the floor of the Grotte des Combarelles has been dug out, so that a person can walk in it, and the tunnel is dimly lit by electric lights. But when the etchings were originally created, some 12,000 or 13,000 years ago, the only way to gain access to the site would have been to crawl, and the only way to see in the absolute dark would have been to carry fire. As I crept along through the gloom, past engravings of wisent and aurochs and woolly rhinos, it occurred to me that I really had no clue what would drive someone to wriggle through a pitch-black tunnel to cover the walls with images that only another, similarly driven soul would see. Yet it also struck me that so much of what is distinctively human was here on display—creativity, daring, “madness.” And then there were the animals pictured on the walls—the aurochs and mammoths and rhinos. These were the beasts that Paleolithic Europeans had hunted and then, one by one, as with the Neanderthals, obliterated.
MICHAEL ROBERTS
The Touchy-Feely (but Totally Scientific!) Methods of Wallace J. Nichols
FROM Outside
THE PHILIPPINE CORAL REEF tank inside the California Academy of Sciences in San Francisco is 25 feet deep and holds 212,000 gallons of water, making it one of the largest exhibits of living coral anywhere in the world. It is the centerpiece of the academy’s Steinhart Aquarium and hosts hundreds of coral species, a couple thousand colorful fish, plus sharks, stingrays, and numerous smaller creatures, like sea anemones and snails. There are five windows affording looks inside, the biggest of which, at 16½ feet tall and almost 30 feet wide, makes a sweeping arc in front of a dimly lit standing area backed by several rows of benches. It was designed to offer visitors a panoramic, theaterlike view of life in the tank and is among the museum’s most popular attractions. It’s Wallace J. Nichols’s favorite spot in the building.
Nichols, forty-four, is a biologist and research associate at the academy who made a name for himself in the mid-1990s when he tracked a loggerhead turtle that swam from Baja, Mexico, to Japan, the first time anyone had recorded an animal swimming an entire ocean. He has done fieldwork in waters around the globe and spends most of his waking hours thinking and talking about the ocean, but when he’s in front of that big window at the aquarium, he doesn’t watch the fish. He watches the people.
“Whether it’s a ninety-two-year-old or a two-year-old, when they come into that blue space, something happens,” Nichols says. They grow quiet and calm, but there’s more to it than that. When couples walk in, they frequently start holding hands. He says that if you ask people here what they’re feeling, they’ll struggle for words. Nichols finds this fascinating. He also believes that if we can understand what really happens to us in the presence of the ocean—which brain processes underlie our emotional reactions—it could bring about a radical shift in conservation efforts. If we learn precisely why we love the ocean, his thinking goes, we’ll have an immensely powerful new tool to protect it.
Not surprisingly, this theory can strike many of his peers as soft. “‘You must be from California.’ That’s the first response,” Nichols says. (He lives north of Santa Cruz, though he was raised in New Jersey.) But Nichols’s credibility as a scientist, along with his charm and passion, have enabled him to rally excitement for his ideas among a diverse constituency of researchers and activists. In the past couple of years, he’s become a sought-after speaker, giving dozens of presentations at a wide mix of venues, from TEDx
to adventure-travel trade shows to environmental symposiums. His pitch: more data on rising sea temperatures or plastic pollution or disappearing creatures won’t do anything for ocean conservation. Instead, we need to study our own minds.
Nichols envisions cognitive neuroscientists constructing detailed models of brain activity for experiences like sitting on a beach, then using their findings to drive public policy. “If I walk into a meeting of a coastal zoning commission and say, ‘I think people listening to the ocean is good for them,’ you’d see all the eyeballs in the room rolling,” says Nichols. “But if I walk in and say, ‘This is my friend the Stanford neuroscientist, and his research using brain scans shows that sitting by the ocean has the same calming effects as meditation on reducing stress,’ suddenly access to the coast becomes a public health issue.”
It’s a viable fantasy that derives from the fact that Nichols himself isn’t a neuroscientist. Unable to test his hypotheses, he’s launched a campaign to create a new field of study he calls neuroconservation. His hope is to inspire cognitive scientists to examine these fundamental questions. As he sees it, it’s a ripe invitation: Who wants to know what happens when our most complex organ meets the planet’s largest feature?
“My role is to be the catalyst and cheerleader,” he says. “But the question is, How do you turn this big idea into a movement?”