SCIENCE
10/25/2014 09:39 am ET Updated Oct 25, 2014

Scientists Pinpoint When Humans Had Sex With Neanderthals

Scientists have long-known that our human ancestors got down and dirty with Neanderthals. But when exactly did this interbreeding first occur?

A study from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany offers a new answer.

For the study, researchers sequenced the genome of a 45,000-year-old modern human male, using a femur bone that was unearthed in 2008 near the small village of Ust’-Ishim in western Siberia. The genome sets the record for being the oldest of a modern human ever sequenced--and the researchers were thrilled to find that it held fragments of Neanderthal DNA.

“This allowed us to estimate that the ancestors of the Ust’-Ishim individual mixed with Neanderthals approximately 7,000-13,000 years before this individual lived or about 50,000 to 60,000 years ago," Dr. Janet Kelso, an evolutionary geneticist at the institute who led the computer-based analyses of the genome, said in a written statement, "which is close to the time of the major expansion of modern humans out of Africa and the Middle East."

Previous studies suggested that interbreeding occurred anywhere from 37,000 to 86,000 years ago, The New York Times reported, and so this new research significantly narrows that estimate.

The research team also compared the Ust'-Ishim man's genome to those of people today from more than 50 populations, discovering that his DNA was more similar to that of non-Africans than Africans, but equally similar to the DNA of present-day Asians and ancient Europeans. It turned out that the ancient man had a similar amount of Neanderthal genes--around two percent--as present-day Eurasians.

This finding raises new questions about when the ancestors of present day Eurasians first migrated out of the continent, which some scientists believe happened around 100,000 years ago.

"There is a dispute as to when that 'Out of Africa' event happened and this fossil helps to look at that," Dr. Christopher Stringer, a paleoanthropologist at the Natural History Museum in London, who was not involved in the research, told BBC News. "It is close to the time I think that modern humans exited from Africa and gave rise to the populations in the rest of the world. I think that exit happened 60,000 years ago."

A study describing the findings was published online on Oct. 22 in the journal Nature.

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