Ancient gene flow from modern humans into Siberian Neanderthals. Gene flow in Neandertals

It has been shown that Neandertals contributed genetically to modern humans outside Africa approximately 47,000-65,000 years ago. Here, we analyze the genomes of a Neandertal and Denisovan from the Altai Mountains in Siberia together with the sequences of chromosome 21 of two Neandertals from Spain and Croatia. We find that a modern human population more than 100,000 years ago contributed genetically to the ancestors of Neandertals from the Altai Mountains. By contrast, we do not detect such a genetic contribution in the Denisovan or the two European Neandertals. We conclude that in addition to later interbreeding events, the ancestors of Neandertals from the Altai Mountains and modern humans met and interbred, possibly in the Near East, many thousands of years earlier than previously reported.