© Beijing Genomics Institute (BGI-Shenzhen)
A researcher collects a blood sample from an ethnic Tibetan man participating in a DNA study looking into mutations that allow Tibetans to live at high altitudes.
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. For instance, when at high altitudes, women who come from low altitudes usually have problems with childbirth, such as preeclampsia, which is potentially dangerous high blood pressure during pregnancy.
"Tibetans have a really good example of a human adaptation to a new environment," said study co-author Rasmus Nielsen, a population and evolutionary geneticist at the University of California, Berkeley.
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. Although most people experience a rise in hemoglobin levels at high altitudes, Tibetans only increase their hemoglobin levels a limited amount - too much hemoglobin in the blood can lead to a greater risk of heart disease.
To learn more about human evolution, Nielsen and his colleagues investigated how Tibetans might have developed their adaptation. Frustratingly, the research team's computer models could not at first explain how Tibetans evolved their pattern of EPAS1 mutations as quickly as they apparently did.