Neanderthal sex boosted immunity in modern humans

[Gerald]

Sexual relations between ancient humans and their evolutionary cousins are critical for our modern immune systems, researchers report in Science journal.

Mating with Neanderthals and another ancient group called Denisovans introduced genes that help us cope with viruses to this day, they conclude.

Previous research had indicated that prehistoric interbreeding led to up to 4% of the modern human genome.

The new work identifies stretches of DNA derived from our distant relatives.

In the human immune system, the HLA (human leucocyte antigen) family of genes plays an important role in defending against foreign invaders such as viruses.

The authors say that the origins of some HLA class 1 genes are proof that our ancient relatives interbred with Neanderthals and Denisovans for a period.

At least one variety of HLA gene occurs frequently in present day populations from West Asia, but is rare in Africans.

The researchers say that is because after ancient humans left Africa some 65,000 years ago, they started breeding with their more primitive relations in Europe, while those who stayed in Africa did not.

"The HLA genes that the Neanderthals and Denisovans had, had been adapted to life in Europe and Asia for several hundred thousand years, whereas the recent migrants from Africa wouldn't have had these genes," said study leader Peter Parham from Stanford University School of Medicine in California.

"So getting these genes by mating would have given an advantage to populations that acquired them."

http://www.bbc.co.uk/news/science-environment-14673047


Note: 26 August 2011 Last updated at 11:15 GMT