Analyses of DNA found in human fossils from around [45,000 years ago] — the oldest known human remains in Europe — suggest that interbreeding between Homo sapiens and Neandertals, who were on the fast track to extinction, occurred more commonly than has often been assumed, two new studies suggest.
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Remains of three H. sapiens individuals unearthed in Bulgaria’s Bacho Kiro Cave yielded nuclear DNA containing Neandertal contributions of about 3 to 4 percent, says a team led by evolutionary geneticist Mateja Hajdinjak of the Francis Crick Institute in London.
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Further evidence of ancient interbreeding comes from a nearly complete human skull discovered in 1950 in a cave in what’s now the Czech Republic. About 2 percent of the genes in DNA from that fossil, identified as a female’s, also come from Neandertals.
If H. sapiens and Neandertals regularly interbred as the latter population neared its demise, then relatively large numbers of incoming humans accumulated a surprising amount of DNA from smaller Neandertal populations, [evolutionary geneticist Charles] Lalueza-Fox suspects. After 40,000 years ago, additional migrations into Europe by people with little or no Neandertal ancestry would have further diluted Neandertal DNA from the human gene pool, he says.
