Tuesday, December 09, 2008

Sapiens, Neandertals Didn't Interbreed

...he and his colleagues will make thrifty use of the rough draft to understand Neanderthal biology, evolution and their relationship to humans - and the big question: did they interbreed or not?

On that question, the answer seems to be probably not. Although the two species seemed to have lived together, if the first European humans regularly interbred with Neanderthals, researchers would expect the genome of modern Europeans to share more similarities with Neanderthals than those of modern Africans.

This is not the case, Briggs says. Europeans and Africans appear to have equal numbers of genetic differences with Neanderthals, suggesting that the first anatomically modern humans to arrive in Europe replaced their close relatives Homo neanderthalensis.

The rough draft is also expected to say some things about Neanderthal biology. "We're starting to be able to answer individual questions about concrete genes," says Briggs.

Preliminary results suggest that Neanderthals were lactose intolerant, hardly surprising since the ability to digest dairy products in adulthood only became common in humans after the domestication of cows, 10,000 years ago.

Neanderthals also seem to lack a mutation associated with increased fertility, identified in Icelanders. A 2005 paper suggested that this mutation had entered humans through inbreeding with Neanderthals.

Nor do Neanderthals boast mutations in a gene called microcephalin, linked to bulging brains in humans. This might shoot down another controversial hypothesis contending that this version of microcephalin also evolved in Neanderthals then spread to humans through inbreeding.

With a draft sequence, Briggs and his team will be able to home in on more genes known to have changed since humans split with chimpanzees, six million years ago, and determine where Neanderthals stand in relation. This will shed light on the evolution of modern humans after their ancestors split from Neanderthals, more than 600,000 years ago.

John Hawks has a don't jump too fast semi rebuttal post.

Introgression from Neandertals doesn't look too promising though.

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