New Ancestor? Scientists Ponder DNA From Siberia

Malcolm Ritter, Google News, March 24, 2010

In the latest use of DNA to investigate the story of humankind, scientists have decoded genetic material from an unidentified human ancestor that lived in Siberia and concluded it might be a new member of the human family tree.

The DNA doesn’t match modern humans or Neanderthals, two species that lived in that area around the same time–30,000 to 50,000 years ago.

Instead, it suggests the Siberian species lineage split off from the branch leading to moderns and Neanderthals a million years ago, the researchers calculated. And they said that doesn’t seem to match the history of human ancestors previously known from fossils.

So the Siberian species may be brand new, although the scientists cautioned that they’re not ready to make that claim yet.

Other experts agreed that while the Siberian species may be new, the case is far from proven.

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The researchers, who say the Siberian species is not a direct ancestor of modern-day people, hope further genetic analysis will show if it’s a new species. Some experts are skeptical about whether such analysis will resolve that.

In any case, the finding emphasizes that quite unlike the present day, anatomically modern humans have often lived alongside their evolutionary relatives, one expert said.

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The new work, published online Wednesday by the journal Nature, is reported by Johannes Krause and Svante Paabo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and others.

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Their analysis indicated the Siberian species last shared a common ancestor with modern humans and Neanderthals about 1 million years ago. That in turn suggested there was a previously unrecognized migration out of Africa around that time, they said.

The work decoded the complete set of DNA from mitochondria, the power plants of cells. That’s different from the better-known DNA that comes from cell nuclei and determines things like eye color. Paabo said the researchers are working to decode nuclear DNA from the Siberian species. That will reveal whether it was closely related to Neanderthals or today’s humans, and answer questions like whether it interbred with Neanderthals or ancestors of modern-day people, he said.

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[“The complete mitochondrial DNA genome of an unknown hominin from southern Siberia,” by Svante Pääbo, Johannes Krause, et al., can be downloaded here. There is a charge.]

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