Genome of extinct Siberian human sheds new light on modern human origins

The sequencing of the nuclear genome from an ancient finger bone found in a Siberian cave shows that the cave dwellers were neither Neandertals nor modern humans. An international team of researchers led by Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig (Germany) has sequenced the nuclear genome from a finger bone of an extinct hominin that is at least 30,000 years old and was excavated by archaeologists from the Russian Academy of Sciences in Denisova Cave in southern Siberia, Russia, in 2008. A team at Harvard Medical School led the population-genetics analysis.

These findings are published in the December 23 issue of Nature.

Earlier this year Svante Pääbo and his colleagues showed that the mitochondrial DNA from the finger bone displayed an unusual sequence suggesting that it came from an unknown ancient hominin form. Now, using techniques the researchers developed to sequence the Neandertal genome earlier this year, they have sequenced the nuclear genome from the bone.

The researchers found that the individual was female and came from a group of hominins that shared an ancient origin with Neandertals, but subsequently diverged. They call this group of hominins Denisovans. Unlike Neandertals, Denisovans did not contribute genes to all present-day Eurasians. However, Denisovans share an elevated number of genetic variants with modern-day Papua New Guinean populations, suggesting that there was interbreeding between Denisovans and the ancestors of Melanesians.

In addition, a Denisovan tooth found in the same cave shows a morphology that is distinct from Neandertals and modern humans and resembles much older hominin forms. Bence Viola, a scientist at the Max Planck Institute of Evolutionary Anthropology comments, "The tooth is just amazing. It allows us to connect the morphological and genetic information."

David Reich, an associate professor at Harvard Medical School who led the population genetic analysis, says, "The fact that Denisovans were discovered in Southern Siberia but contributed genetic material to modern human populations from New Guinea suggests that Denisovans may have been widespread in Asia during the Late Pleistocene."

According to Svante Pääbo of the Max Planck Institute of Evolutionary Anthropology, "In combination with the Neandertal genome sequence, the Denisovan genome suggests a complex picture of genetic interactions between our ancestors and different ancient hominin groups."

Source: Harvard Medical School