High-altitude adaptation

Organisms can live at high altitude, either on land, in water, or while flying. Decreased oxygen availability and decreased temperature make life at such altitudes challenging, though many species have been successfully adapted via considerable physiological changes. As opposed to short-term acclimatisation (immediate physiological response to changing environment), high-altitude adaptation means irreversible, evolved physiological responses to high-altitude environments, associated with heritable behavioural and genetic changes. Among animals, only few mammals (such as yak, ibex, Tibetan gazelle, vicunas, llamas, mountain goats, etc.) and certain birds are known to have completely adapted to high-altitude environments.

Human populations such as the Tibetans, the South Americans and the Ethiopians live in the otherwise uninhabitable high mountains of the Himalayas, Andes and Ethiopia respectively. The adaptation of humans to high altitude is an example of natural selection in action.

High-altitude adaptations provide examples of convergent evolution, with adaptations occurring simultaneously on three continents. Tibetan humans and Tibetan domestic dogs share a genetic mutation, EPAS1, but it has not been seen in Andean humans.

...
Wikipedia