Neanderthals, the heavy-browed relatives of modern humans, spread out across Europe and Asia about 200,000 years ago. But when did they die out?
A new analysis of Neanderthal sites from Spain to Russia provides the most definitive answer yet: about 40,000 years ago, at least in Europe.
That is thousands of years earlier than some scientists have suggested, and it sharply narrows the period that Neanderthals and modern humans overlapped in Europe.
“After that, we don’t think there are any Neanderthals on the continent anymore,” said Thomas Higham, the deputy director of the radiocarbon accelerator unit at the University of Oxford in England.
The findings, reported Wednesday in the journal Nature, run counter to assertions that pockets of Neanderthals persisted in Spain until just 30,000 years ago, even as modern humans spread outward.
“This is a very strong compilation,” said Chris Stringer, who leads research on human origins at the Natural History Museum in London and who was not involved in the research. “I think it kind of replaces the picture we had before.”
In 1995, researchers — including Jean-Jacques Hublin, now at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany —
Hublin said he had changed his mind as better radiocarbon dates became available.
“To me, I’m ready to buy the new date,” he said.
Modern humans migrated out of Africa at least 60,000 years ago, and anthropologists have been trying to figure out what happened when the two groups encountered each other.
The recent analysis of Neanderthal DNA shows that Neanderthals and modern humans not only crossed paths, but that they also interbred. For non-African people living today, 1 to 4 percent of their genome has Neanderthal origins.
The interbreeding appears to have occurred about 50,000 to 60,000 years ago somewhere in western Asia.
“You’ve kind of got two parts of the story,” Stringer said. “There must have been a western Asia coexistence, which included interbreeding. Then there was a later coexistence in Europe, for which we have no evidence of interbreeding but possible evidence of some cultural contact between the groups.”
In the Nature paper, Higham and his colleagues took advantage of advances in radiocarbon dating in testing samples of bone, charcoal, and shell from 40 sites, mostly in Western Europe. The dating method takes advantage of unstable radioactive carbon 14 atoms produced from the bombardment of the atmosphere by cosmic rays from outer space. The radioactive carbon combines with oxygen atoms to form carbon dioxide, and plants and animals take up some of it as long as they are alive.
But as soon as they die, they absorb no additional radioactive carbon, and the carbon 14 disappears over time. The ratio of carbon 14 to carbon 12, which is stable, thus tells the age and can be used to date bones and artifacts up to about 50,000 years ago.
Contaminants containing younger organic molecules can distort the dating by thousands of years. The researchers prepared samples that would extract collagen in the bone and remove the contaminants.
Higham said his team would like to expand the research to Neanderthal sites in Eastern Europe and across Russia to Siberia. It is possible that Neanderthals persisted later in those areas.
Some of the conclusions are tentative because many of the sites do not have bones of the actual inhabitants, and paleontologists are still debating whether it was Neanderthals or modern humans who used the tools found at the sites.
The findings so far indicate that Neanderthals did not disappear all at once.
“I think we’ll see patchy disappearance prior to extinction,” Higham said.