A gene that originated from an extinct species of humans is attributed to Tibetans' ability to adapt to high altitudes, according to a recent study.

The research discovered that EPAS1, the gene unique to the Denisovans, allowed the body to regulate the production of hemoglobin that controls the amount of oxygen carried in the blood.

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"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, around the same time as the more well-known Neanderthals, under pressure from modern humans," said UC Berkeley professor of integrative biology Rasmus Nielsen.

Blood samples from 40 Tibetans and 40 Han Chinese were compared to 1,000 other individuals representing 26 human populations in the Human Genome Diversity Panel, the Sydney Morning Herald learned.

The study found that almost 90 percent of Tibetans had the high-altitude gene similar to the one found in the 41,000-year-old Denisovan finger bone and two teeth previously discovered in a Siberian cave. Only two out of the 40 Han Chinese showed evidence of the EPAS1 gene.

"Our findings may suggest that the exchange of genes through mating with extinct species may be more important in human evolution than previously thought," Nielsen said.

He noted that this is the first time a gene from another human species has proven to have helped present-day humans adapt to the environment.

The researchers also said that Denisovans in Eurasia on their way to China may have mated with the early modern humans travelling out of Africa.

At high altitudes, haemoglobin and red blood cell levels typically rise to high degrees, thereby thickening the blood and leading to heart complications such as heart attacks, hypertension and stroke.

Tibetans with the EPAS1 gene were found to have only slightly raised levels of haemoglobin and red blood cells which prevent the side effects normally experienced by those who have the common variant of the gene.

The study was published in the journal, Nature, on July 2.

TagsDenisovan, Science, Tibet, Han Chinese, Human Genome Diversity Panel, nature, Gene, evolution, Rasmus Nielsen, EPAS1, haemoglobin