How do Tibetans survive at high altitudes of more than 13,000 feet (4,000 meters)? Surviving at such high elevations is dangerous due to the lack of oxygen in high mountains. When we go to high altitudes where there is scarcity of oxygen, a common form of gene increase hemoglobin and red blood cell production. It increases the thickness of blood, leading to deadly consequences such as hypertension, heart attacks and strokes.
Tibetans inherited a special blood-diluting gene from Denisovans
So, why doesn’t that happen with Tibetans? Scientists have discovered that these people have inherited a special blood-diluting gene from an extinct human species, which helps them cope with life at high altitudes. This variant of the gene increases the level of hemoglobin and red blood cells, but only slightly, at higher altitudes. Therefore, Tibetans don’t suffer from any side effects.
Scientists found that Tibetans inherited this gene from Denisovans, a human species that lived around 50,000 years ago. Two teeth and a single finger bone of Denisovans species were found in a Siberian cave. DNA testing of these 41,000-year old samples revealed that Denisovans were different from Neanderthals and our species.
Ramus Nielsen, a biology professor at the University of California, Berkeley, said that the exchange of genes took place through mating with the extinct species. And this variant of the gene became widespread after people moved to high altitude regions like Tibet several thousand years ago. Today, about 87% Tibetans have this high altitude variant of the gene. It is also present in 9% of Han Chinese, who have common ancestors as Tibetans.
This gene has been found only in Tibetans
The study was published in the journal Nature. It’s the first time a study has shown that a gene from archaic human species has unequivocally helped modern humans to adapt to different environments. Professor Nielsen said such exchange of genes may have helped modern humans adjust to new living conditions as they spread out of Africa to the rest of the world.
Scientists believe early modern humans spreading out of Africa en route to China interbred with Denisovans in Eurasia. Their descendants still have a small percentage of Denisovan DNA.