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Friday, May 7, 2010

A little Neanderthal in all of us

OK, only in those of us who don’t have African ancestry. Scientists from the Max Planck Institute for Evolutionary Biology are in the process of sequencing the Neanderthal genome. With 60% of the genome sequenced, the answer to a longstanding question is in: Neanderthals and humans did interbreed, and the evidence is present in our genomes.

Neanderthals were closely related hominids (so close, that some paleontologists consider them to be the same species as modern humans) that lived in Asia and Europe until about 30,000 years ago. The question of whether humans and Neanderthals interbred has plagued paleontologists for decades. Until recently, researchers did not possess the tools to answer that question. Now, the ability to extract DNA from 40,000 year-old bone fragments combined with rapid sequencing techniques has made that question answerable.

The picture, as implied by the DNA evidence is this: About 500,000 years ago, the common ancestor of both humans and Neanderthals left Africa, and eventually settled in Europe and Asia, evolving into Neanderthals along the way. Meanwhile, that same ancestor back in Africa was busy evolving into modern humans. Around 100,000 years ago, some of those remaining humans left Africa and joined the already present Neanderthals in the Middle East. Some good will gestures occurred between the two peoples, and the result is that all non-Africans carry between one and four percent Neanderthal DNA in their genomes. Modern humans whose ancestors remained in Africa do not have any Neanderthal DNA. On the other hand, people of Asian or European descent all have the same amount of Neanderthal DNA, indicating that the tête-à-têtes occurred before modern humans spread throughout those regions.

File:Sapiens neanderthal comparison.jpg

Comparison of Neanderthal and Modern human skulls from the Cleveland Museum of Natural History
Photo Credit: hairymuseummatt, 15 November 2008

Hat tip: Cathy Earle.