Science and Health
New ancestor? Scientists ponder DNA from Siberia
(Agencies)
Updated: 2010-03-25 13:15
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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.
They describe mapping DNA from what appeared to be a youngster's pinkie finger bone, which had been recovered in 2008 from Denisova Cave in Altai Mountains of southern Siberia. They showed how it differed from DNA of 54 modern-day people and six Neanderthals.
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.
Without a completed analysis of the nuclear DNA, "we are not saying this is a new species," Paabo said, although he said that's a likely possibility.
Rick Potts, director of the Smithsonian Institution's Human Origins Program, said the Siberian find might represent Homo heidelbergensis or Homo erectus. And even analysis of the Siberian species' nuclear DNA won't show if it's distinct from those ancestors, he said.
As for the study's suggestion of a migration out of Africa about a million years ago, Potts said there's already evidence of one or two migrations around that time.
The finger bone recovered from the Siberian species is not enough for a fossil-to-fossil comparison with other ancient species to show whether it's a new species, Delson said.
He suspects it might be a descendant of Homo erectus that's already documented in some fossil remains in northern Africa and Europe. Scientists are still trying to figure out how many species of the Homo grouping those bones represent and what name or names to attach to them, he said.
Disotell said the new creature could be an early version of Homo antecessor, a forerunner of Neanderthals and modern humans known from fossils in Spain. Or, he said, it could be a new species. In fact, the eventual decision could hinge mostly on the philosophical question of just how different a creature has to be to be declared a new species, he said.
Potts said that in the new work, "what we're seeing is a really, really interesting distant echo of the DNA history of human evolution.... This is an amazingly powerful technique that these guys have. This is going to be a growth industry in the study of human evolution."
