for National Geographic News
Trace your family tree all the way back to Stone Age Europe, and you may find Neandertals among your ancestors.
A new study suggests that modern humans and Neandertals (often spelled Neanderthals) interbred fairly regularly and even mingled physical features as Homo sapiens spread across Europe some 35,000 years ago.
The findings, based on ancient human bones from a cave in Romania, add to the long-running debate as to why Neandertals, a heavy-browed, thickset species of human, eventually went extinct. (Related: "Neandertals' Last Stand Was in Gibraltar, Study Suggests" [September 13, 2006].)
Some scientists argue that Neandertals were slaughtered or out-competed by ancestors of modern humans once they reached Europe after first emerging in Africa.
But the new research, reported today in the Proceedings of the National Academy of Sciences, supports the idea of a more intimate relationship, with Neandertals becoming absorbed into the human race through interbreeding.
Researchers from Romania and the U.S. dated fossil bones found at Petera Muierii ("Cave of the Old Woman") to around 30,000 years ago, the period when Neandertals and modern humans overlapped (map of Romania).
While the remains are largely typical of modern humans, they also show some distinctly Neandertal traits, says team member Erik Trinkaus, an anthropologist at Washington University in St. Louis, Missouri.
These telltale skeletal features include the shape of the lower jaw and the back of the skull, Trinkaus says.
"[These features] are extremely unlikely to have come from earlier modern humans and very likely have come from Neandertals," Trinkaus said.
The Neandertal-type jaw features are not related to eating but are "anatomical peculiarities," he said.
The skull characteristic noted in the study is related to braincase development, he adds, and is found in around half of humans known from the same time period.
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