We already knew modern humans had interbred with the Neanderthals before they disappeared from history (See the Cosmos cover story The Neanderthals live on in us). But new research from Svante Pääbo at the Max Planck Institute in Germany and David Reich at Harvard Medical School suggests that the interbreeding took place more recently than previously thought.
DNA analysis of a jawbone of a human who lived in Europe about 40,000 years ago shows that it belonged to a modern human, but with a stronger Neanderthal ancestry than has been observed before.
“We show that one of the very first modern humans that is known from Europe had a Neanderthal ancestor just four to six generations back in his family tree,” says Pääbo.
“He carries more Neanderthal DNA than any other present-day or ancient modern human seen to date.”
Neanderthals lived in Europe until about 35,000 years ago, disappearing at the same time modern humans were spreading across the continent.
“We know that before 45,000 years ago, the only humans in Europe were Neanderthals. After 35,000 years ago, the only humans in Europe were modern humans. This is a dramatic transition,” Reich says.
The jawbone, uncovered in Romania in 2002, was determined by radiocarbon dating to be between 37,000 and 42,000 years old.
No artifacts were discovered nearby, so anthropologists had no cultural clues about who the individuals were or how they lived.
The physical features of the jawbone were predominantly those of modern humans, but it also had some Neanderthal traits.
Pääbo and Reich teamed up to investigate that possibility by analysing DNA from the jawbone using methods pioneered in Pääbo’s lab.
The analysis showed the individual was more genetically similar to present-day East Asians and Native Americans than present-day Europeans.
“This sample, despite being in Romania, doesn’t yet look like Europeans today,” Reich says.
“It is evidence of an initial modern human occupation of Europe that didn’t give rise to the later population. There may have been a pioneering group of modern humans that got to Europe, but was later replaced by other groups.”