It turns out that modern humans have a more complicated past than scientists realized. Researchers have discovered that populations of Homo sapiens swapped DNA in at least two regions of the world with a mysterious group of hominids known as Denisovans.
The Denisovans appear to have made a contribution to the modern human gene pool ― not nearly as significant as the Neanderthals, but notable.
Denisovans date back as far as 50,000 years ago, based on tests of a little Denisovan girl’s finger bone and a bit of molar discovered in a Siberian cave in 2008. The new species was called Denisovan after the name of the cave in the Altai mountains.
Scientists managed in 2016 to trace DNA of the Denisovans to some Melanesians — who live in Papua New Guinea and other Pacific islands — who were found to have 5 percent of Denisovan ancestry. Some East and South Asians have close to 0.2 percent. (Neanderthals have contributed between 1 percent and 4 percent of the genome in people in several continents.)
But after a new DNA survey of humans, scientists from the University of Washington in Seattle were surprised to discover a new distinct set of Denisovan ancestry among some modern East Asians — particularly among Han Chinese, Chinese Dai and Japanese. This Denisovan DNA is more closely related to the sample from the fossils discovered in Siberia, according to the study published in the journal Cell.
The discovery demonstrates that there were at least two distinct populations of Denisovans living in Asia, and likely somewhat geographically distant.
Harvard DNA researcher David Reich, who was not involved in the study, called the research a “breakthrough.”
“It’s a definite third interbreeding event,” adding to the previously known Denisovan and Neanderthal mixtures, he told The Washington Post. He said other scientists using a similar DNA survey method might discover additional cross-breeding.
“I am sure there are others,” he told the Post.