[Source: John Easton, Medical Center Public Affairs] -- The largest study to date of genetic variation among chimpanzees has found that the traditional, geography-based sorting of chimps into three populations—western, central and eastern—is underpinned by significant genetic differences, two to three times greater than the variation between the most different human populations. In the April issue of the journal PLoS Genetics, researchers from the University, the Broad Institute of MIT and Harvard, and Arizona State University show there has been very little detectable admixture between the different populations. “Finding such a marked difference between the three groups has important implications for conservation,” said Molly Przeworski, Assistant Professor in Human Genetics and the College, and a senior author of the study. “It means we have to protect three separate habitats, all threatened, instead of just one.”
To unravel the evolutionary history to chimpanzees, the research team collected DNA from 78 common chimpanzees and six bonobos, a separate species of chimpanzee, and examined 310 DNA markers from each. They found four “discontinuous populations.” “We saw little evidence of migration between groups in the wild,” said Celine Becquet, first author of the paper and a graduate student in Przeworski’s laboratory. “Part of that could stem from the gaps in our samples, but we think most of this separation is genuine, a long-term consequence of geographic isolation.” The original boundaries between groups may have been the emergence and growth of rivers, such as the Congo River, which is thought to be about 1.5 million years old. “Chimps don’t swim,” Becquet explained. “For them, water provides a very effective border.” An ongoing loss of habitat has increased the physical separation between the three groups.
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