People living in Tibet have developed special adaptations, allowing their bodies to better function in high-altitude conditions. This is the conclusion of a new study examining residents of the Tibetan plateau.
Most humans have challenges breathing and exerting themselves at high altitudes. There are also more serious consequences of high-altitude exposure for migrants from lower altitudes, including thrombosis - blood clots in veins. Tibetan people were found to have low levels of hemoglobin. This is the iron-bearing metalloprotein in the blood of all vertebrates that carries oxygen around the body.
Researchers wanted to know why the people of Tibet are so well-adapted to living and working 13,000 feet above sea level. In addition to lower levels of hemoglobin, researchers found the people of the Tibetan plateau had changes on two of their genes that control oxygen usage - EGLN1 and EPAS1. This genetic change may be as recent as just 3,000 years ago. Two other genes, HYOU1 and HMBS, also show evidence of adaptation to the great altitude of the area.
The study was conducted by researchers from the University of Chicago and Case Western Reserve University. The team included Anna Di Rienzo of the University of Chicago, and graduate student Choongwon Jeong.
"The Tibetan genome appears to arise from a mixture of two ancestral gene pools. One migrated early to high altitude and adapted to this environment. The other, which migrated more recently from low altitudes, acquired the advantageous alleles from the resident high-altitude population by interbreeding and forming what we refer to today as Tibetans," Di Rienzo said.
Researchers believe the adaptations may have been present in the people of the Tibetan plateau for as long as 30,000 years. When people arrived from other areas, they interbred with the local population. This passed the adaptations onto their descendants.
"This is a good example of evolution as a tinkerer. We see other examples of admixtures. Outside of Africa, most of us have Neanderthal genes - about two to five percent of our genome - and people today have some immune system genes from another ancient group called the Denisovans," Cynthia Beall, anthropology professor at Case Western Reserve University and co-author of the article, said.
The group studied genetic data from 69 Sherpas from Nepal, and 96 unrelated people living on the Tibetan plateau. They then compared the data to known genomes from around the world. The Human Genome Diversity Panel and HapMap3 databases were scoured for control data, and integrated into the study.
According to the study, modern Tibetans have descended from an interbreeding of Sherpa and Han Chinese.
Details of the study were published in the journal Nature Communications on 10 February.
