ANCESTOR IN HAND: the sequencing of the Neandertal genome has shown that humans who live outside Africa today carry DNA from Neandertals. Here Svante Paabo, who led the sequencing effort, holds a Neandertal skull.Image: Frank Vinken Researchers sequencing Neandertal DNA have concludedthat between 1 and 4 percent of the DNA of people today who live outside Africa came from Neandertals, the result of interbreeding between Neandertals and early modern humans.A team of scientists led by Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig pieced together the first draft of the sequence—which represents about 60 percent of the entire genome—using DNA obtained from three Neandertal bones that come from Vindija cave in Croatia and are more than 38,000 years old. The researchers detail their analysis of the sequence in the May 7 Science. The evidence that Neandertals contributed DNA to modern humans came as a shock to the investigators. “First I thought it was some kind of statistical fluke,” Pääbo remarked during a press teleconference on May 5. “We as a consortium came into this with a very, very strong bias against gene flow,” added team member David Reich of Harvard University. But when the researchers conducted additional analyses
billiga canada goose jackor, the results all pointed to the same conclusion.Rethinking the Gene PoolThe finding contrasts sharply with Pääbo's previous work. In 1997 he and his colleagues sequenced the first Neandertal mitochondrial DNA . Mitochondria are the cell’s energy-generating organelles, and they have their own DNA, which is distinct from the much longer DNA sequence that resides in the cell’s nucleus. Their analysis revealed that Neandertals had not made any contributions to modern mitochondrial DNA. Yet because mitochondrial DNA represents only a tiny fraction of an individual’s genetic makeup, the possibility remained that Neandertal nuclear DNA might tell a different story. Still, additional genetic analyses have typically led researchers to conclude that Homo sapiens arose in Africa and replaced the archaic humans it encountered as it spread out from its birthplace without mingling with them.But mingle they apparently did
nike free billig, according to the new study. When Pääbo’s team looked at patterns of nuclear genome variation in present-day humans, it identified 12 genome regions where non-Africans exhibited variants that were not seen in Africans and that were thus candidates for being derived from the Neandertals, who lived not in Africa but Eurasia. Comparing those regions with the same regions in the newly assembled Neandertal sequence
abercrombie & fitch jackets, the researchers found 10 matches, meaning 10 of these 12 variants in non-Africans came from Neandertals. (Where the other two segments came from remains unknown.)Intriguingly, the researchers failed to detect a special affinity to Europeans—a link that might have been expected given that Neandertals seem to have persisted in Europe longer than anywhere else before disappearing around 28,000 years ago. Rather
mulberry bayswater, the Neandertal sequence was equally close to sequences from present-day people from France
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Botas timberland, even though no Neandertal specimens have turned up in the latter two parts of the world. By way of explanation, the investigators suggest that the interbreeding occurred in the Middle East between 45,000 and 80,000 years ago, before moderns fanned out to other parts of the Old World and split into different groups.Bolstering Multiregional Theory?Intermixing does not surprise paleoanthropologists who have long argued on the basis of fossils that archaic humans, such as the Neandertals in Eurasia and Homo erectus in East Asia, mated with early moderns and can be counted among our ancestors—the so-called multiregional evolution theory of modern human origins. The detection of Neandertal DNA in present-day people thus comes as welcome news to these scientists. “It is important evidence for multiregional evolution,” comments Milford H. Wolpoff of the University of Michigan, the leading proponent of the theory. Topics related articles：
