Ancient DNA from Peştera cu Oase demonstrates inbreeding no more than four to six generations previously
The cave site of Peştera cu Oase (‘Cave with Bones’) in Romania has yielded some of the earliest fossil remains of modern humans in Europe. The remains of three individuals recovered from the site include a largely-complete lower jawbone (Oase 1), the near-complete skull of a 15-year-old adolescent, and a left temporal bone. The remains are around 40,000 years old and exhibit a mosaic of modern and archaic features. Modern features include the absence of browridges, a narrow nasal aperture, and a prominent chin; but there are also archaic features such as a wide dental arcade and very large molars. There is little doubt that they are modern humans and not Neanderthals, but some aspects of the morphology are consistent with Neanderthal ancestry.
Researchers have now recovered ancient DNA from the Oase 1 jawbone and sequenced the genome. They report that between 6 to 9 percent of the genome is of Neanderthal origin, a higher percentage than for any other modern human genome sequenced to date. Three chromosomal segments of Neanderthal DNA are of considerable length, suggesting that the Neanderthal contribution to the Oase 1 individual occurred so recently in their past that the chromosomal segments of Neanderthal origin had little time to break up due to recombination. The researchers turned their attention to seven segments of the genome that appeared to be of recent Neanderthal origin and from the genetic lengths of these, implied that Oase 1’s Neanderthal ancestor had lived no more than four to six generations earlier, or less than two hundred years.
The existence of such a recent Neanderthal ancestor casts doubts on theories that suggest that interbreeding occurred only very occasionally, or was confined to an early episode soon after modern humans first left Africa. However, the researchers failed to establish a clear relationship between the Oase 1 individual and later modern humans in Europe, suggests that they may have been a member of an early modern human population in Europe that eventually died out without contributing much to later European populations.
Fu, Q. et al., An early modern human from Romania with a recent Neanderthal ancestor. Nature 524, 216-219 (2015).