Research showing that our species interbred with Neanderthals some 100,000 years ago is providing intriguing evidence that Homo sapiens ventured out of Africa much earlier than previously thought, although the foray appears to have fizzled.
Scientists said on Wednesday an analysis of the genome of a Neanderthal woman whose remains were found in a cave in the Altai Mountains in southern Siberia near the Russia-Mongolia border detected residual DNA from Homo sapiens, a sign of inter-species mating.
Previous research had established that Homo sapiens and our close cousins the Neanderthals interbred around 50,000 to 60,000 years ago, said geneticist Sergi Castellano of the Max Planck Institute for Evolutionary Anthropology in Germany.
The new study, published in the journal Nature, indicates that additional interbreeding also occurred tens of thousands of years earlier.
Our species arose in Africa roughly 200,000 years ago and later migrated to other parts of the world.
Geneticist Martin Kuhlwilm of Spain's Universitat Pompeu Fabra, who worked on the study at the Max Planck Institute, said a very likely scenario explaining the Homo sapiens DNA in the Neanderthal woman's genome is that a small population of our species trekked out of Africa and encountered Neanderthals in the Middle East, and interbreeding occurred there.
Failed dispersal from Africa
Their journey appears to have been what researchers called a failed dispersal from Africa, with no descendants going on to colonize Europe, Asia and points beyond.
"We don't know what happened to them. It seems likely that this population went extinct, either by environmental changes or maybe direct competition with Neanderthals," Kuhlwilm said.
"This seems to have happened during a much earlier migration out of Africa than previously thought. It implies that modern humans left Africa in several waves, some of which probably went extinct."
The robust, large-browed Neanderthals prospered across Europe and Asia from about 350,000 years ago until shortly after 40,000 years ago, disappearing in the period after our species established itself in the region.
Despite an outdated reputation as our dimwitted cousins, scientists say Neanderthals were highly intelligent, with
complex hunting methods, likely use of spoken language and symbolic objects, and sophisticated fire usage.
Neanderthal interbreeding with Homo sapiens had a lasting impact on human genetics. A study published last week in the journal Science revealed a link between residual Neanderthal DNA in the human genome and traits in people including depression, nicotine addiction, blood-clotting and skin lesions.