Remains of a Neanderthal woman who lived around 100,000 years ago in the Altai Mountains of Siberia reveal that human and Neanderthals mated much earlier than previously thought.
One or more of her relatives were actually humans, a new study shows.
It has been known that Neanderthals contributed DNA to modern humans, so people today of European and Asian descent retain Neanderthal DNA in their genomes, but the Neanderthal woman offers the first evidence that gene flow from interbreeding went from modern humans into Neanderthals as well.
Photos: Faces of Our Ancestors
The study, published in the journal Nature, "is also the first to provide genetic evidence of modern humans outside Africa as early as 100,000 years ago," Sergi Castellano, who co-led the study and is a researcher at the Max Planck Institute for Evolutionary Anthropology, told Discovery News.
Given the now closely intertwined histories of Neanderthals and Homo sapiens, Castellano added that "it is better to refer to Neanderthals and modern humans as two different human groups, one archaic and one modern, and not different species."
Earlier research determined that Neanderthals and modern humans met and mated outside of Africa sometime between 47,000–65,000 years ago. The Siberian woman shows that such interbreeding could have happened as early as 120,000 years ago, since it is now believed modern humans and Neanderthals were both then present in the region around the Persian Gulf and in the area where the following countries are now located: Cyprus, Egypt, Israel, Lebanon, Syria and Turkey.
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Castellano, Martin Kuhlwilm and colleagues analyzed the Siberian woman's DNA and identified portions of her genome that match sequences taken from people who are now living in Africa. The researchers also analyzed the remains of a Denisovan individual and the remains of two Neanderthals that were found in European caves (one from Croatia, and the other from Spain). No modern human DNA was detected in those three other individuals.
The scientists therefore think that a population of Neanderthals likely migrated from Europe through the Near East, where mating with modern humans occurred. They then continued to travel up into the Altai Mountains, where the climate was much milder 125,000 years ago than it is now.
Castellano and his team further believe that the modern humans who were in the Near East at this early time eventually died out and did not contribute to the present day Homo sapiens genome.
Nevertheless, Castellano said, "Some Asians and Oceanians (living today) have more Neanderthal DNA because a second pulse of admixture might have happened with Neanderthals."