Adaptations to High Altitude
The two major human populations that have adapted well to high altitude, the Tibetans and Andeans, have strikingly different phenotypes.” (West, 2012 p. 1229). The founders of contemporary indigenous highland populations moved into their stressful environment with an ancient oxygen homeostasis toolkit that we share with all multicellular animals. Our oldest single-celled ancestors evolved in the hypoxic conditions of the early oceans, our vertebrate and mammalian ancestors evolved in atmospheres with as little as 12% atmospheric oxygen at some times – compared with 21% today. Individuals experience hypoxia during normal intrauterine life, sleep, and wound healing. Our oxygen homeostasis genetic and molecular toolkit consists of ancient elements that have functioned for hundreds of millions of years. These considerations could reasonably lead to a hypothesis that human biology retains ample capacity to adapt to chronic, lifelong high-altitude hypoxia. Indeed, an estimated 90 million or more residents at 2500m or higher demonstrate such a capacity. However, populations in different geographic areas appear to have undergone further evolution and adaptation during the past 5 – 35,000 years (depending on location) with the result that they have somewhat different biological characteristics. This talk covers different patterns of adaptive biological characteristics among high-altitude native populations and the accumulating evidence explaining why and how those different responses came about.