Modern Humans Interbred With Two More Archaic Humans

The fact that modern humans or the Homo sapiens were involved in interbreeding with very near species has become well established by now. It has also been established that modern humans had interbred with Neanderthals and Denisovans—two archaic human species that are no more in this world. But their presence is still being borne in the DNAs of the modern humans. Humans still have 2% of Neanderthal genes in their DNA.

A latest research published in PNAS now says that modern humans interbred with two other extinct early human species. Joao Teixeira of the University of Adelaide, Australia, and the lead author of the PNAS paper, said, “Each of us carry within ourselves the genetic traces of these past mixing events. These archaic groups were widespread and genetically diverse, and they survive in each of us. Their story is an integral part of how we came to be.”

When modern humans emerged in Africa and started migrating, they spread throughout Eurasia. What they found there was that Eurasia was already occupied by older hominins like Neanderthals and the Denisovans. In their voyage outside Africa, modern humans often got involved in interbreeding with these archaic species. The 2% Neanderthal genes in the modern human DNA indicates that Neanderthal mixing happened with modern humans soon after they migrated out Africa. These events probably occurred 50,000 to 55,000 years back in the middle east.

Also read: Prehistoric Cave Woman Was An Offspring Of Two Different Species Of Archaic Humans

Modern humans moved farther east and also landed up in the islands of Southeast Asia. Here they seem to have encountered more hominin species. "At least three other archaic human groups appear to have occupied the area, and the ancestors of modern humans mixed with them before the archaic humans became extinct,"—said Teixeira. One of these groups was the Denisovans, but the other two still remain elusive.

The two unknown hominin species have been named as EH1 and EH2.

The first unknown extinct hominin, EH1 was genetically equidistant from Denisovans and Neanderthals. What is interesting is the fact that the ancestors of all Asians and Australo-Papuan populations bred with EH1 and that’s the reason these populations share 2.6 to 3.4% EH1 ancestry.

It is now fading, but the genetic signals can still be detected in the DNAs of Aboriginal Australians, East Asians and Andaman Islanders. This led to a very interesting revelation, that the EH1 hominins most likely occupied a region in northern India. Here a group of modern humans, the branch that continued migrating towards Asia, Australia and the Papuan Islands encountered the EH1 ( in the map below the branch 1).

The interbreeding events with the Denisovans that occurred in East Asia, Sunda Shelf and Philippines can be traced on the branches 2, 3, and 4 in the map below.

Map is taken form Science Alert. This map is created by Teixeira et al. 

The second extinct hominin species, the EH2 interbred with modern humans in Flores, but the evidence is less clear though. This appears in short-statured people living near Liang Bua Cave, the place where the Homo floriensis was discovered. The branch 5 in the map above signifies this.

More findings in this line reveal a very complicated and tangled human history. “We knew the story out of Africa wasn't a simple one, but it seems to be far more complex than we have contemplated. The Island Southeast Asia region was clearly occupied by several archaic human groups, probably living in relative isolation from each other for hundreds of thousands of years before the ancestors of modern humans arrived," Texeira said.