In a major breakthrough, US researchers have found a genetic cause - a single DNA base pair change that dates back 8,000 years - that contributes to the Tibetans' ability to live in low-oxygen conditions.
The researchers found that the newly-identified genetic variation protects Tibetans by decreasing the over-response to low oxygen.
"These findings help us understand the unique aspects of Tibetan adaptation to high altitudes and to better understand human evolution," said senior study author Josef Prchal, a professor of internal medicine at the University of Utah.
In an environment where others struggle to survive, Tibetans thrive in the thin air on the Tibetan Plateau with an average elevation of 14,800 feet.
About 8,000 years ago, the gene EGLN1 changed by a single DNA base pair.
"Today, 88 percent of Tibetans have the genetic variation and it is virtually absent from closely related lowland Asians," Prchal added.
For the study, Prchal travelled several times to Asia to obtain permissions to recruit subjects for the study but failed.
He found a help in Tsewang Tashi from Huntsman Cancer Institute at University of Utah.
Later, Prchal received a long-awaited letter of support from the Dalai Lama.
The two factors were instrumental in engaging the Tibetans' trust: more than 90 Tibetans volunteered for the study.
"Because oxygen plays a central role in human physiology and disease, a deep understanding of how high altitude adaptations work may lead to novel treatments for various diseases, including cancer," Prchal said.
The study was published online in the journal Nature Genetics.