Friday, July 27, 2012

Another Variety of Human Found in African DNA

Today's discovery in human genetics:
The human family tree just got another — mysterious — branch, an African “sister species” to the heavy-browed Neanderthals that once roamed Europe. While no fossilized bones have been found from these enigmatic people, they did leave a calling card in present-day Africans: snippets of foreign DNA.

 There’s only one way that genetic material could have made it into modern human populations. “Geneticists like euphemisms, but we’re talking about sex,” said Joshua Akey of the University of Washington in Seattle, whose lab identified the mystery DNA in three groups of modern Africans.

These genetic leftovers do not resemble DNA from any modern-day humans. The foreign DNA also does not resemble Neanderthal DNA, which shows up in the DNA of some modern-day Europeans, Akey said. That means the newly identified DNA came from an unknown group. “We’re calling this a Neanderthal sibling species in Africa,” Akey said. He added that the interbreeding probably occurred 20,000 to 50,000 years ago, long after some modern humans had walked out of Africa to colonize Asia and Europe, and around the same time Neanderthals were waning in Europe.
Very exciting, if it turns out to be true. But it is exactly what we should expect. Evolution generally works by branching, not by change within a single line of descent. So during the period of rapid change that led to the appearance of fully modern humans, we should expect that many different species or sub-species would appear. And that is exactly what the genetics seems to show. As to how that DNA got into the human line, I quote a friend of mine: "one thing history shows is that people will fuck anything."

The study was based on detailed sequencing of the DNA from fifteen Africans, five from each of three hunter-gatherer groups. Just as interesting as the possible new human species is the great diversity represented by he sample, with 3 million genetic variations never documented before.

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