The gene, called EPAS1, is activated when oxygen levels in the blood drop, triggering production of more haemoglobin
Beijing : Tibetans are able to live at high altitudes thanks to a gene picked up when their ancestors mated with a species of human they helped push to extinction, according to a new study, reports PTI.
This is the first time a gene from another species of human has been shown unequivocally to have helped modern humans adapt to their environment, researchers said.
An unusual variant of a gene involved in regulating the body’s production of haemoglobin became widespread in Tibetans after they moved onto the high-altitude plateau several thousand years ago.
This variant allowed them to survive despite low oxygen levels at elevations of 15,000 feet or more, whereas most people develop thick blood at high altitudes, leading to cardiovascular problems.
“We have very clear evidence that this version of the gene came from Denisovans,” a mysterious human relative that went extinct 40,000-50,000 years ago under pressure from modern humans, said principal author Rasmus Nielsen, a University of California, Berkeley professor.
“This shows very clearly and directly that humans evolved and adapted to new environments by getting their genes from another species,” said Nielsen.
The gene, called EPAS1, is activated when oxygen levels in the blood drop, triggering production of more haemoglobin.
The gene has been referred to as the “superathlete” gene because at low elevations, some variants of it help athletes quickly boost haemoglobin and thus the oxygen-carrying capacity of their blood, upping endurance. At high altitudes, however, the common variants of the gene boost haemoglobin and its carrier, red blood cells, too much, increasing the thickness of the blood and leading to hypertension and heart attacks as well as other conditions.
The variant, or allele, found in Tibetans raises haemoglobin and red blood cell levels only slightly at high elevations, avoiding the side effects seen in most people who relocate to elevations above 13,000 feet.