DNA links humans, mystery species

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The human family tree just got another -- mysterious -- branch, an African "sister species" to the heavy-browed Neanderthals who 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 way one 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 foreign 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 likely 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.

Akey said that present-day Europeans show no evidence of the foreign DNA, meaning the mystery people were likely confined to Africa.

The find offers more evidence that for thousands of years, modern-looking humans shared the Earth with evolutionary cousins who later died out. And when the groups met, they did what came naturally -- they bred.

The once controversial idea that humans mated with other species is now widely accepted among scientists. In fact, hominid hanky-panky seems to have occurred wherever humans met others who looked kind of like them.

In 2010, researchers from the Max Planck Institute for Evolutionary Anthropology in Germany announced finding Neanderthal DNA in the genomes of modern Europeans.

Neanderthals -- heavy-set people whose thick double brows, broad noses and flat faces set them apart from modern humans -- disappeared around 25,000 to 30,000 years ago.

Another mysterious group of extinct people recently identified from a finger bone in Siberia -- known as the Denisovans -- also left some of their DNA in modern-day Pacific Islanders.

And while modern humans and the newly found "archaic" Africans might be classified as distinct species, they managed to produce viable offspring. Likewise, donkeys and horses, lions and tigers, and whales and dolphins can mate and make babies.

"They had to be similar enough in appearance to anatomically modern humans that reproduction would happen," said Akey. But with no fossils in hand, it's impossible to say what these people looked like. It's also impossible to say whether the matings were consensual or forced.

But one thing is clear: This enigmatic group left their DNA all across Africa. The researchers found it in the forest-dwelling pygmies of central Africa and in two groups of hunter-gatherers on the other side of the continent -- the Hadza and Sandawe people of Tanzania.

Read more: http://www.azcentral.com/news/articles/2012/07/26/20120726dna-links-humans-mystery-species.html#ixzz21qFnhDuq

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