A new ancestor in Siberia?

News broke this past week of bone fragments discovered in Siberia that could add a new branch to the human tree.

The fragments, part of a youngster’s pinkie finger bone, were discovered in Denisova Cave in the Altai Mountains of southern Siberia.  By sampling the DNA from the finger bone, scientists were able to compare it with both human and Neanderthal genetic sequences.  But the DNA doesn’t match either modern humans or Neanderthals, two species that lived in that area around the same time – 30,000 to 50,000 years ago.

Scientists believe the discovery, referred to as both the Denisova hominin and X-Woman, represents a hitherto unknown type of hominin that shares a common ancestor with anatomically modern human and Neanderthal dating back approximately 1.0 million years ago. This indicates that it derives from a hominin migration out of Africa distinct from that of the ancestors of Neanderthals and of modern humans.

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

Todd Disotell of New York University, who was familiar with the new work, 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.

Further reading:

Nature – The complete mitochondrial DNA genome of an unknown hominin from southern Siberia
BBC – DNA identifies new ancient human dubbed ‘X-woman’
National Geographic – New type of human discovered via single pinky finger

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