Extinct, Ancient Human Cousin Gave Tibetans the Gene to Survive at High Altitudes

Tibetans have the unusual ability to breathe and adapt to high altitudes. Now, scientists have found that these people possess this ability thanks to a gene that they picked up when their ancient ancestors mated with a species of human they helped pushed to extinction.

The gene in question is an unusual variant involved in regulating the body's production of hemoglobin, a molecule that carries oxygen in the blood. This particular gene became widespread in Tibetans after they moved onto the high-altitude plateau of Tibet several thousand years ago. Despite low oxygen levels at this elevation, the Tibetans were able to survive due to this unusual gene variant. Yet where did the gene come from in the first place? That's a good question.

The researchers believe that the gene came from Denisovans, a somewhat mysterious human relative that went extinct somewhere between 40,000 to 50,000 years ago. This was around the same time as Neanderthals also disappeared due to pressure from modern humans.

The gene, called EPAS1, is activated when oxygen levels in the blood drop. This triggers production of more hemoglobin. This causes the thickness of the blood to increase, which can lead to hypertension and heart attacks; yet in Tibetans, the hemoglobin and red blood cell levels are raised only slightly, which allows them to avoid these negative side effects.

"We found part of the EPAS1 gene in Tibetans is almost identical to the gene in Denisovans and very different from all other humans," said Rasmus Nielsen, one of the researchers, in a news release. "We can do a statistical analysis to show that this must have come from Denisovans. There is no other way of explaining the data."

The findings reveal that humans managed to accumulate genes from other species. Not only that, but it also indicates that there may be other species from which we also got our DNA.

The findings are published in the journal Nature.