Gibbons 2010 - Review of Green et al (Neandertal Genome)

Gibbons 2010 - Review of Green et al (Neandertal Genome) -...

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7 MAY 2010 VOL 328 SCIENCE www.sciencemag.org 680 IT’S THE MYSTERY OF MOUNT CARMEL. ON this limestone ridge overlooking the coast of Israel, modern humans lived in caves off and on for tens of thousands of years, start- ing more than 100,000 years ago. Then, per- haps as early as 80,000 years ago, members of another species reached and occupied the caves: heavy-bodied Neandertals, who were escaping a cold spell in Europe and moving south into the Middle East. Did the two spe- cies meet here? Did they mate? The archaeological record in the caves is ambiguous on that question, and anthropolo- gists have fought bitterly over it. Some claim that the anatomy of fossils shows that Nean- dertals, our closest cousins, did mate with modern humans, either in the Middle East or in Europe. But others thought modern humans coming out of Africa completely replaced Neandertals with little or no interbreeding. And the genetic evidence from ancient bones showed no sign that Neandertals had swapped genes with our ancestors—until now. On page 710, an international team of researchers presents their fi rst detailed anal- ysis of the draft sequence of the Neandertal genome, which now includes more than 3 bil- lion nucleotides collected from the bones of three female Neandertals who lived in Croa- tia more than 38,000 years ago. By comparing this composite Neandertal genome with the complete genomes of fi ve living humans from different parts of the world, the researchers found that both Europeans and Asians share 1% to 4% of their nuclear DNA with Neandertals. But Afri- cans do not. This suggests that early modern humans interbred with Nean- dertals after moderns left Africa, but before they spread into Asia and Europe. The evi- dence showing interbreeding is “incontrovert- ible,” says paleoanthropologist John Hawks of the University of Wisconsin, Madison, who was not involved in the work. “There’s no other way you can explain this.” As a result, many people living outside Africa have inherited a small but signifi cant amount of DNA from these extinct humans. “In a sense, the Neandertals are then not altogether extinct,” says lead author Svante Pääbo, a paleogeneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who was surprised to nd he was part Neandertal. “They live on in some of us.” The team also used the Neandertal DNA like a probe to find the genes that make us modern. Even though the genomes of humans and Neandertals are 99.84% iden- tical, the researchers identifi ed regions that have changed or evolved since our ancestors and Neandertals diverged sometime between 270,000 and 440,000 years ago—their new, slightly younger estimate of the split. So far, the team has detected tantalizing differences in genes involved in metabolism, skin, the skeleton, and the development of cogni- tion, although no one knows yet how these genetic changes affect physiology. “This is a groundbreaking study!” enthuses evolution- ary geneticist Hendrik Poinar of McMaster University in Hamilton, Canada. “We can
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Gibbons 2010 - Review of Green et al (Neandertal Genome) -...

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