PALO ALTO, Calif., Aug. 25 (UPI) — Human interbreeding with our ancient evolutionary cousins endowed the human gene pool with beneficial versions of immune system genes, U.S. researchers say.
Scientist at Stanford University say interbreeding of humans with Neanderthals and another close relative, the recently discovered Denisovans, had a positive effect on modern human fitness by introducing a percentage of the DNA of our ancient cousins into modern human populations.
“The cross breeding wasn’t just a random event that happened, it gave something useful to the gene pool of the modern human,” Peter Parham, a professor of microbiology and immunology, said in a Stanford release Thursday.
The useful contribution, he said, was the introduction of new variants of immune system genes called the HLA class I genes, critical for our body’s ability to recognize and destroy pathogens.
Modern humans, Neanderthals and Denisovans share a common ancestor in Africa, but the groups split into separate, distinct populations around 400,000 years ago.
Neanderthals migrated northwestward into West Asia and Europe, while Denisovans moved northeastward into East Asia.
The ancestors of modern man remained in Africa until around 65,000 years ago, when they expanded into Eurasia and encountered the other human-like groups and interbreeding took place, researchers said.