A Neanderthal Skeleton in the Homo Sapien Closet?

That possibility was revived last week when two groups of scientists reported that they had deciphered DNA from the thigh bone of a Neanderthal man who lived in Croatia 38,000 years ago. From their analysis of genetic material in the bone, the scientists estimated that Neanderthals and the modern people who supplanted them had 99.5% of their genes in common.

Since the discovery in the 19th century of Neanderthal remains in Germany's Neander Valley, scientific opinion has seesawed between the idea that Neanderthals were an evolutionary dead end only distantly related to modern humans and the view that at least some Neanderthals felt the urge to merge with smarter, nimbler modern humans who left Africa about 100,000 years ago. Unfortunately, the new revelations about Neanderthal DNA don't settle the question.

A skull was recently found in Pestera cu Oase — the Cave with Bones — in southwestern Romania, along with other human remains. Radiocarbon dating indicates it is at least 35,000 years old and may be more than 40,000 years old.

The researchers said the skull had the same proportions as a modern human head and lacked the large brow ridge commonly associated with Neanderthals. However, there were also features that are highly unusual among modern humans, such as frontal flattening, a fairly large bone behind the ear and exceptionally large upper molars, which are seen among Neanderthals and other early hominids.

"Such differences raise important questions about the evolutionary history of modern humans," said co-author Joao Zilhao of the University of Bristol, England.

That view is not without its critics and Dr. Richard Potts of the Smithsonian's National Museum of Natural History, while noting that the skull represents the earliest modern human ever found in Europe added “It's a big deal in that sense,” he said,

“but the combination of characteristics doesn't necessarily indicate interbreeding between populations.”

“Overall there is no strong evidence for mixing of Neanderthal and modern human populations and this doesn't add any," said Potts, who wasn't part of the research team.

“None of the features cited as unusual in modern humans is exclusively Neanderthal,” Potts said, adding “Rather, they could be features passed down from earlier populations in Africa.”

Oponents point to the fact that humans and chimpanzees have 96% of their genes in common, but as more Neanderthal remains become available for genetic testing, the question will no doubt be studied further.