Neanderthals

Last of the Neanderthals
Eurasia was theirs alone for 200,000 years.
Then the newcomers arrived.

Reconstruction by Kennis & Kennis/Photograph by Joe McNally

In March of 1994 some spelunkers exploring an extensive cave system in northern Spain poked their lights into a small side gallery and noticed two human mandibles jutting out of the sandy soil. The cave, called El Sidrón, lay in the midst of a remote upland forest of chestnut and oak trees in the province of Asturias, just south of the Bay of Biscay. Suspecting that the jawbones might date back as far as the Spanish Civil War, when Republican partisans used El Sidrón to hide from Franco's soldiers, the cavers immediately notified the local Guardia Civil.

But when police investigators inspected the gallery, they discovered the remains of a much larger—and, it would turn out, much older—tragedy.

Within days, law enforcement officials had shoveled out some 140 bones, and a local judge ordered the remains sent to the national forensic pathology institute in Madrid. By the time scientists finished their analysis (it took the better part of six years), Spain had its earliest cold case. The bones from El Sidrón were not Republican soldiers, but the fossilized remains of a group of Neanderthals who lived, and perhaps died violently, approximately 43,000 years ago. The locale places them at one of the most important geographical intersections of prehistory, and the date puts them squarely at the center of one of the most enduring mysteries in all of human evolution.

The Neanderthals, our closest prehistoric relatives, dominated Eurasia for the better part of 200,000 years. During that time, they poked their famously large and protruding noses into every corner of Europe, and beyond—south along the Mediterranean from the Strait of Gibraltar to Greece and Iraq, north to Russia, as far west as Britain, and almost to Mongolia in the east. Scientists estimate that even at the height of the Neanderthal occupation of western Europe, their total number probably never exceeded 15,000. Yet they managed to endure, even when a cooling climate turned much of their territory into something like northern Scandinavia today—a frigid, barren tundra, its bleak horizon broken by a few scraggly trees and just enough lichen to keep the reindeer happy.

By the time of the tragedy at El Sidrón, however, the Neanderthals were on the run, seemingly pinned down in Iberia, pockets of central Europe, and along the southern Mediterranean by a deteriorating climate, and further squeezed by the westward spread of anatomically modern humans as they emerged from Africa into the Middle East and beyond. Within another 15,000 years or so, the Neanderthals were gone forever, leaving behind a few bones and a lot of questions. Were they a clever and perseverant breed of survivors, much like us, or a cognitively challenged dead end? What happened during that period, roughly 45,000 to 30,000 years ago, when the Neanderthals shared some parts of the Eurasian landscape with those modern human migrants from Africa? Why did one kind of human being survive, and the other disappear?

On a damp, fog-shrouded morning in September 2007, I stood before the entrance to El Sidrón with Antonio Rosas of the National Museum of Natural Sciences in Madrid, who heads the paleoanthropological investigation. One of his colleagues handed me a flashlight, and I gingerly lowered myself into the black hole. As my eyes adjusted to the interior, I began to make out the fantastic contours of a karstic cave. An underground river had hollowed out a deep vein of sandstone, leaving behind a limestone cavern extending hundreds of yards, with side galleries spidering out to at least 12 entrances. Ten minutes into the cave, I arrived at the Galería del Osario—the "tunnel of bones." Since 2000, some 1,500 bone fragments have been unearthed from this side gallery, representing the remains of at least nine Neanderthals—five young adults, two adolescents, a child of about eight, and a three-year-old toddler. All showed signs of nutritional stress in their teeth—not unusual in young Neanderthals late in their time on Earth. But a deeper desperation is etched in their bones. Rosas picked up a recently unearthed fragment of a skull and another of a long bone of an arm, both with jagged edges.

"These fractures were—clop—made by humans," Rosas said, imitating the blow of a stone tool. "It means these fellows went after the brains and into long bones for the marrow."

In addition to the fractures, cut marks left on the bones by stone tools clearly indicate that the individuals were cannibalized. Whoever ate their flesh, and for whatever reason—starvation? ritual?—the subsequent fate of their remains bestowed upon them a distinct and marvelous kind of immortality. Shortly after the nine individuals died—possibly within days—the ground below them suddenly collapsed, leaving little time for hyenas and other scavengers to scatter the remains. A slurry of bones, sediment, and rocks tumbled 60 feet into a hollow limestone chamber below, much as mud fills the inside walls of a house during a flood.

There, buffered by sand and clay, preserved by the cave's constant temperature, and sequestered in their jewel cases of mineralized bone, a few precious molecules of the Neanderthals' genetic code survived, awaiting a time in the distant future when they could be plucked out, pieced together, and examined for clues to how these people lived, and why they vanished.

The first clue that our kind of human was not the first to inhabit Europe turned up a century and a half ago, about eight miles east of Düsseldorf, Germany. In August 1856 laborers quarrying limestone from a cave in the Neander Valley dug out a beetle-browed skullcap and some thick limb bones. Right from the start, the Neanderthals were saddled with an enduring cultural stereotype as dim-witted, brutish cavemen. The size and shape of the fossils does suggest a short, stout fireplug of a physique (males averaged about five feet, five inches tall and about 185 pounds), with massive muscles and a flaring rib cage presumably encasing capacious lungs. Steven E. Churchill, a paleoanthropologist at Duke University, has calculated that to support his body mass in a cold climate, a typical Neanderthal male would have needed up to 5,000 calories daily, or approaching what a bicyclist burns each day in the Tour de France. Yet behind its bulging browridges, a Neanderthal's low-domed skull housed a brain with a volume slightly larger on average than our own today. And while their tools and weapons were more primitive than those of the modern humans who supplanted them in Europe, they were no less sophisticated than the implements made by their modern human contemporaries living in Africa and the Middle East.

One of the longest and most heated controversies in human evolution rages around the genetic relationship between Neanderthals and their European successors. Did the modern humans sweeping out of Africa beginning some 60,000 years ago completely replace the Neanderthals, or did they interbreed with them? In 1997 the latter hypothesis was dealt a powerful blow by geneticist Svante Pääbo—then at the University of Munich—who used an arm bone from the original Neanderthal man to deliver it. Pääbo and his colleagues were able to extract a tiny 378-letter snippet of mitochondrial DNA (a kind of short genetic appendix to the main text in each cell) from the 40,000-year-old specimen. When they read out the letters of the code, they found that the specimen's DNA differed from living humans to a degree suggesting that the Neanderthal and modern human lineages had begun to diverge long before the modern human migration out of Africa. Thus the two represent separate geographic and evolutionary branches splitting from a common ancestor. "North of the Mediterranean, this lineage became Neanderthals," said Chris Stringer, research leader on human origins at the Natural History Museum in London, "and south of the Mediterranean, it became us." If there was any interbreeding when they encountered each other later, it was too rare to leave a trace of Neanderthal mitochondrial DNA in the cells of living people.

Pääbo's genetic bombshell seemed to confirm that Neanderthals were a separate species—but it does nothing to solve the mystery of why they vanished, and our species survived.

One obvious possibility is that modern humans were simply more clever, more sophisticated, more "human." Until recently, archaeologists pointed to a "great leap forward" around 40,000 years ago in Europe, when the Neanderthals' relatively humdrum stone tool industry—called Mousterian, after the site of Le Moustier in southwestern France—gave way to the more varied stone and bone tool kits, body ornaments, and other signs of symbolic expression associated with the appearance of modern humans. Some scientists, such as Stanford University anthropologist Richard Klein, still argue for some dramatic genetic change in the brain—possibly associated with a development in language—that propelled early modern humans to cultural dominance at the expense of their beetle-browed forebears.

But the evidence in the ground is not so cut and dried. In 1979 archaeologists discovered a late Neanderthal skeleton at Saint-Césaire in southwestern France surrounded not with typical Mousterian implements, but with a surprisingly modern repertoire of tools. In 1996 Jean-Jacques Hublin of the Max Planck Institute in Leipzig and Fred Spoor of University College London identified a Neanderthal bone in another French cave, near Arcy-sur-Cure, in a layer of sediment also containing ornamental objects previously associated only with modern humans, such as pierced animal teeth and ivory rings. Some scientists, such as British paleoanthropologist Paul Mellars, dismiss such modern "accessorizing" of a fundamentally archaic lifestyle as an "improbable coincidence"—a last gasp of imitative behavior by Neanderthals before the inventive newcomers out of Africa replaced them. But more recently, Francesco d'Errico of the University of Bordeaux and Marie Soressi, also at the Max Planck Institute in Leipzig, analyzed hundreds of crayon-like blocks of manganese dioxide from a French cave called Pech de l'Azé, where Neanderthals lived well before modern humans arrived in Europe. D'Errico and Soressi argue that the Neanderthals used the black pigment for body decoration, demonstrating that they were fully capable of achieving "behavioral modernity" all on their own.

"At the time of the biological transition," says Erik Trinkaus, a paleoanthropologist at Washington University in St. Louis, "the basic behavior [of the two groups] is pretty much the same, and any differences are likely to have been subtle." Trinkaus believes they indeed may have mated occasionally. He sees evidence of admixture between Neanderthals and modern humans in certain fossils, such as a 24,500-year-old skeleton of a young child discovered at the Portuguese site of Lagar Velho, and a 32,000-year-old skull from a cave called Muierii in Romania. "There were very few people on the landscape, and you need to find a mate and reproduce," says Trinkaus. "Why not? Humans are not known to be choosy. Sex happens."

It may have happened, other researchers say, but not often, and not in a way that left behind any evidence. Katerina Harvati, another researcher at the Max Planck Institute in Leipzig, has used detailed 3-D measurements of Neanderthal and early modern human fossils to predict exactly what hybrids between the two would have looked like. None of the fossils examined so far matches her predictions.

The disagreement between Trinkaus and Harvati is hardly the first time that two respected paleoanthropologists have looked at the same set of bones and come up with mutually contradictory interpretations. Pondering—and debating—the meaning of fossil anatomy will always play a role in understanding Neanderthals. But now there are other ways to bring them back to life.

Two days after my first descent into El Sidrón cave, Araceli Soto Flórez, a graduate student at the University of Oviedo, came across a fresh Neanderthal bone, probably a fragment of a femur. All digging immediately ceased, and most of the crew evacuated the chamber. Soto Flórez then squeezed herself into a sterile jumpsuit, gloves, booties, and plastic face mask. Under the watchful eyes of Antonio Rosas and molecular biologist Carles Lalueza-Fox, she delicately extracted the bone from the soil, placed it in a sterile plastic bag, and deposited the bag in a chest of ice. After a brief stop in a hotel freezer in nearby Villamayo, the leg bone eventually arrived at Lalueza-Fox's laboratory at the Institute of Evolutionary Biology in Barcelona. His interest was not in the anatomy of the leg or anything it might reveal about Neanderthal locomotion. All he wanted from it was its DNA.

Prehistoric cannibalism has been very good for modern-day molecular biology. Scraping flesh from a bone also removes the DNA of microorganisms that might otherwise contaminate the sample. The bones of El Sidrón have not yielded the most DNA of any Neanderthal fossil—that honor belongs to a specimen from Croatia, also cannibalized—but so far they have revealed the most compelling insights into Neanderthal appearance and behavior. In October 2007 Lalueza-Fox, Holger Römpler of the University of Leipzig, and their colleagues announced that they had isolated a pigmentation gene from the DNA of an individual at El Sidrón (as well as another Neanderthal fossil from Italy). The particular form of the gene, called MC1R, indicated that at least some Neanderthals would have had red hair, pale skin, and, possibly, freckles. The gene is unlike that of red-haired people today, however—suggesting that Neanderthals and modern humans developed the trait independently, perhaps under similar pressures in northern latitudes to evolve fair skin to let in more sunlight for the manufacture of vitamin D. Just a few weeks earlier, Svante Pääbo, who now heads the genetics laboratory at the Max Planck Institute in Leipzig, Lalueza-Fox, and their colleagues had announced an even more astonishing find: Two El Sidrón individuals appeared to share, with modern humans, a version of a gene called FOXP2 that contributes to speech and language ability, acting not only in the brain but also on the nerves that control facial muscles. Whether Neanderthals were capable of sophisticated language abilities or a more primitive form of vocal communication (singing, for example) still remains unclear, but the new genetic findings suggest they possessed some of the same vocalizing hardware as modern humans.

All this from a group of ill-fated Neanderthals buried in a cave collapse, soon after they were consumed by their own kind.

"So maybe it's a good thing to eat your conspecifics," says Pääbo.