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article image400,000-year-old bone raises new questions on human evolution

By Martin Laine     Dec 6, 2013 in Science
A fossilized thigh bone found by scientists in a cave in Spain turned out not to be from a Neanderthal as they had expected, but from a Denisovan, a different group of extinct early humans.
What makes the find so puzzling is that the only previous Denisovan remains have been found in Siberia, 4,000 miles away, and date back only 80,000 years. To heighten the mystery, the fossilized skeleton is anatomically similar to Neanderthals, but the mitochondrial DNA is predominantly Denisovan.
“Our expectation was that it would be a very early Neanderthal. Right now, we’ve generated a big question mark,” said Matthias Meyer, a geneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, in an article in the New York Times.
The cave in Spain where the bones were found is called Sima de los Huesos (“The cave of the bones”}. Since the 1970s scientists have been bringing out fossils dating back hundreds of thousands of years, including 28 nearly complete skeletons.
The technology used to trace the genome of the DNA found in the bone has only recently be developed.
"Our results show that we can now study DNA from human ancestors hundreds of thousands of years old. It is tremendously exciting," said Svante Paabo, director of the Max Planck Institue for Evolutionary Anthropology, in an article in the Science Daily News.
At first some thought there might have been some kind of mistake.
“Everybody had a hard time believing it at first,” Meyer said. “So we generated more and more data to nail it down.”
The discovery doesn’t fit well with the story of human evolution that has been emerging from other previous finds. Most scientists agreed that modern humans, Neanderthals, and Denisovans shared a common ancestor that lived in Africa about 300,000. While Homo sapiens — modern humans — developed in Africa, the Neanderthals migrated west while Denisovans headed East.
“Now we have to re-think the whole story,” said Juan Luis Arsuaga, a paleoanthropologist at Universidad Complutense de Madrid. “It’s extremely hard to make sense of. We still are a bit lost here.”
Meyer and Arsuaga co-authored a study of their findings in the journal Nature. The scientists will now focus their efforts on extracting DNA from other individuals found at the site.
More about Neanderthals, Evolution, Dna
 
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