Ancestors Had Sex with Mysterious Human Cousins

[theshee]

Neanderthals weren't the only ancient cousins that humans frequently mated with, according to a new study that finds that East Asian populations share genes with a mysterious archaic hominin species that lived in Siberia 40,000 years ago.

This group, the Denisovans, is known only by a few bone fragments: A finger bone, a tooth and possibly a toe bone, which is still undergoing analysis. The Denisovans likely split off from the Neanderthal branch of the hominin family tree about 300,000 years ago, but little else is known about their appearance, behavior or dress. But just as researchers have learned that ancient humans and Neanderthals mated, they've also found genetic echoes of the Denisovans in modern residents of Pacific islands, including New Guinea and the Philippines.

The new research expands the Denisovan genetic influence, uncovering Denisovan genes in modern East Asian populations. The genetic signal is less strong than it is in the Oceanic islands such as the Philippines, said study researcher Mattias Jakobsson, a professor of evolutionary biology at Uppsala University in Sweden. On the Asian mainland, the genetic similarities to Denisovans are strongest in southern China and Southeast Asia.

"We are actually finding gene flow in Southeast Asia," Jakobsson told LiveScience. "So it's not restricted to the Oceanian parts of the world."

Jakobsson and his colleagues first ran complex computer simulations of genetic data to understand how the limited gene information collected in population genetics research, which includes just segments of DNA, might be biased. With that understanding, the group then examined genetic data from more than 1,500 modern humans from all over the world.

Comparing that modern data with the Denisovan genome revealed that Asians, especially Southeast Asians, have a higher proportion of Denisovan-related gene variants than other world populations except for the Oceanic islanders. While Oceanians have about a 5 percent fraction of Denisovan-related ancestry, Southeast Asians have around 1 percent, the researchers report today (Oct. 31) in the journal Proceedings of the National Academy of Sciences. In comparison, genes from modern non-African humans have about a 2.5 percent fraction of Neanderthal ancestry.

It's hard to tell when the Denisovan and human interbreeding occurred, Jakobsson said, but since Europeans don't have Denisovan ancestry, it's likely the mating occurred around 23,000 to 45,000 years ago, after Southeast Asians and European populations diverged.

Jakobsson and his colleagues are working on further studies on early human genetics and the steps that led to the modern human genome. The more digging scientists do, the more complex the genetic picture becomes, he said. Notably, bits of genes are almost all that are left behind of some ancient populations, including the Denisovans, he said.

"We don't really know what they looked like, how they behaved or anything like that," Jakobsson said. "It's really genetics that gives us an edge here."
www.livescience.com/16806-asian-ancestors-mated-denisovans.html

[brillbilly]

humans still mate with other things,even animals in the 21centry shee,lol

But seriously this is fascinating stuff
Interbreeding with other human species

Modern humans (Homo sapiens) migrated out of Africa between 55,000-60,000 years ago. An intriguing question for scientists has been whether they interbred with other human species as they spread out around the rest of the world.

Last May, scientists obtained genetic evidence that showed that modern humans outside of Africa share genetic information with Neanderthals, Homo neanderthalensis, which suggests that they must have interbred (Neanderthals died out about 30,000 years ago). And now Denisova genes have also been added to the human genetic mix. But how much interbreeding went on?

Stringer says ‘In terms of actual interbreeding events, on present data there might only have been two: one in the Middle East, perhaps 60,000 years ago, that input about 2.5% Neanderthal genes into recent humans outside Africa; and a subsequent one in south east Asia that added an additional 5% or so of Denisovan DNA into the ancestors of modern Melanesians.


Skull of Homo heidelbergensis, the ancient human species that may be the ancestor of the mystery Denisovan human.

‘If the populations were very small, that component [5% Denisovan genes] might represent as few as 50 Denisovans mixing with 1000 pre-Melanesians, but it was sufficient to give the present-day inhabitants of places like New Guinea and Bougainville as much as 8% “archaic” genes - a small Neanderthal component they acquired first, probably in western Asia, and an additional Denisovan component they acquired later, on their long journey towards Melanesia.

‘While these results do not challenge the notion that everyone alive today traces most of their genetic heritage to a recent African origin, as shown by our mitochondria, Y-chromosomes etc, when we get down to the fine resolution of the whole genome, the story has undoubtedly got a whole lot more complicated,’ says Stringer.
www.nhm.ac.uk/about-us/news/2011/january/ancient-denisovans-and-the-human-family-tree93500.html