Homo sapiens' sex with extinct species was no one-night stand

Sunday, 20 March 2016

Our species, Homo sapiens, has a more adventurous sexual history than previously realised, and all that bed-hopping long ago has left an indelible mark on the human genome.

Scientists have discovered that Homo sapiens - that's us - made more babies with the archaic human like species than first thought. 

An analysis of genetic information from about 1500 people from all over the world indicate that the ancestors of modern humans interbred with Neanderthals and another extinct human species known as Denisovans.

Researchers have found that Asians, Europeans and the Melanesians of Papua New Guinea had Neanderthal and Denosivian ancestry. 

It has also been determined that some of the genes inherited from these extinct species were beneficial for our species.

Many are involved in the immune system and likely helped protect against pathogens, and some play important roles in skin and hair biology, said University of Washington evolutionary geneticist Joshua Akey, who helped lead the study published in the journal Science.

The researchers analysed DNA sequences from 35 people living on Northern Island Melanesia, off the coast of Papua New Guinea. These Melanesians were found to have about 2 percent Neanderthal ancestry, plus an additional genetic contribution of about 2 to 4 per cent from Denisovans.

The non-African populations studied had roughly 1.5 to 4 percent Neanderthal genetic ancestry, Akey said. African populations do not have either Neanderthal or Denisovan ancestry because those two species were never on that continent.

Relatively little is known about Denisovans, which were related to Neanderthals, but were genetically distinct.

Denisovans, discovered in the past decade, are known only from a pinky finger bone and two teeth from a northern Siberian cave.

The fact that the only known Denisovan remains come from northern Siberia, but that their genetic contribution is seen in people living far away in Melanesia suggests Denisovans had a broad geographic range extending across Asia, Akey said.

The robust, large-browed Neanderthals prospered across Europe and Asia from about 350,000 years ago until disappearing shortly after 40,000 years ago. 

Binghamton University molecular anthropologist D Andrew Merriwether said the researchers also detected a contribution to people's genome from a fourth, unknown source.

'So this paints a picture of probably at least four species of hominins (our species and extinct human species) alive at the same time and interbreeding at times over the last 100,000 years.

'Definitely not something most people supposed before 10 years ago,' Merriwether said.