Scientists Estimate Date When Neanderthals and Modern Humans Last Shared Ancestors
Thu, Oct 04, 2012
Modern humans and Neanderthals mixed it up after modern humans left Africa.
Scientists Estimate Date When Neanderthals and Modern Humans Last Shared Ancestors
When the Neanderthal genome was sequenced in 2010 it revealed that people outside Africa share slightly more genetic variants with Neandertals than Africans do. One scenario that could explain this observation is that modern humans interbred with Neanderthals when they emerged from Africa. An alternative scenario is that African populations ancestral to both Neanderthals and modern humans remained subdivided over a few hundred thousand years and that those more related to Neanderthals subsequently left Africa.
To discover why Neandertals are most closely related to people outside Africa, Harvard and Max Planck Institute scientists have estimated the date when Neanderthals and modern Europeans last shared ancestors. The research, published in the journal PLOS Genetics, provides a historical context for the interbreeding. It suggests that it occurred when modern humans carrying Upper Paleolithic technologies encountered Neanderthals as they expanded out of Africa.
Dr. Sriram Sankararaman and colleagues measured the length of DNA pieces in the genomes of Europeans that are similar to Neanderthals. Since recombination between chromosomes when egg and sperm cells are formed reduces the size of such pieces in each succeeding generation, the Neanderthal-related pieces will be smaller the longer they have spent in the genomes of present-day people. In this way, they function as a "genetic clock".
The team estimate that Neanderthals and modern humans last exchanged genes between 37,000 and 86,000 years ago, well after modern humans appeared outside Africa but potentially before they started spreading across Eurasia. This suggests that Neanderthals (or their close relatives) had children with the direct ancestors of present-day people outside Africa.
The report is published as "Sankararaman S, Patterson N, Li H, Pääbo S, Reich D (2012) The Date of Interbreeding between Neandertals and Modern Humans. PLoS Genet 8(10):e1002947. doi:10.1371/journal.pgen.1002947" in PLoS ONE at
http://www.plosgenetics.org/doi/pgen.10029347.
Source: PLoS ONE Library of Science
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Cover Photo: Comparison of Modern Human and Neanderthal skulls from the Cleveland Museum of Natural History. hairymuseummatt (original photo), DrMikeBaxter (derivative work), Wikimedia Commons
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