Genetic mutations from an extinct human lineage help Tibetans and Sherpas live at high altitudes, researchers say.
The new findings add to growing evidence that interbreeding with other human lineages provided genetic variations that helped modern humans adapt as they spread across the world.
As modern humans migrated out of Africa, they had to adapt to many new environments. One noteworthy adaptation was of Tibetans adjusting to the thin air of the Tibetan plateau, which at about 2.5 miles (4 kilometers) in altitude has oxygen levels just 60 percent that of air at sea level. [High & Dry: Images of the Himalayas and Tibetan Plateau]
Recent studies revealed how Tibetans adapted to high altitudes — a pattern of mutations in the gene EPAS1, which influences levels of hemoglobin, the protein in blood that carries oxygen around the body. To learn more about human evolution, researchers investigated how Tibetans might have developed that pattern of mutations.
The researchers looked for the pattern in 26 different modern human populations across the world, as well as in the genomes of Neanderthals and another extinct lineage of human ancestors known as Denisovans. They found that only the Denisovans possessed this haplotype, too, as did a small percentage of Han Chinese. This suggests that the ancestors of Tibetans inherited the EPAS1 mutation pattern from either the Denisovans or the relatives of Denisovans.
The researchers suggest this pattern of mutations might also exist in other Asian populations adapted to high altitudes. These include the Sherpas of Nepal and certain Mongolian populations.
The findings are detailed in the July 3 issue of the journal Nature.