High-Altitude Biological Adaptation

In Lorna Grindlay Moore’s, and Judith G. Regensteiner’s paper entitled Adaptation to High Altitude, the authors write about the biological problems that humans face who live at high altitudes. They outline the challenges that hhumans living at high altitudes today experience largely due to the low levels of oxygen in the air. In fact, the oxygen supply is reduced by one-half at the highest altitudes at which human populations reside. This reduction in oxygen intake can cause serious and life-long health issues.

This paper points to a multitude of problems that are prevalent in populations from high altitudes, some that can even lead to death. These include reduced fecundity, problems during pregnancy, childhood growth retardation, high-altitude pulmonary edema, chronic mountain sickness and emphysema. With all these health risks, one would assume that high altitudes would not be popular places to live. However, today, at least 30 million people live and successfully reproduce at elevations over 7,500 feet and people have done so for thousands of years.

Hypoxia (a condition in which the body is deprived of adequate oxygen supply) of high altitudes cannot be ameliorated by culture. This distinguishes hypoxia from other harsh environmental conditions like extreme cold or heat. In addition, it created an ideal environment for studying natural selection because all of the people in a population have access to the exact same amount of oxygen. Today, there are only four regions of the world in which groups of humans reside at elevations above 2500 meters: the Rocky Mountains in North America, the Andes of South America, the Ethiopian Highlands of Eastern Africa, and the Himalayas of South-Central Asia.

Scientists feel that natural selection has had enough time to increase the frequency of adaptive alleles in mountain populations who live in all four of these areas except the Rocky Mountains. Research has been done with populations that have inhabited the Andean and Tibetan Plateaus for millennia and scholars have identified distinctive morphological and physiological characteristics thought to offset the stress of high-altitude hypoxia. These adaptations include thin-walled pulmonary vasculature, relative hypoventilation of Andean high-altitude natives or the elevated exhaled nitric oxide of Tibetans.

Scientists now feel that there is enough evidence to show that people who have lived in these high altitudes for long periods of time have developed adaptations resulting from natural selection favoring more effective adaptive responses to hypoxia. Yes, there are those who can say that their ancestors have lived in a high-altitude environment for thousands of years, but not many. The implications for the health of many people who live in high altitudes are obvious. As stated by Moore and Regensteiner, many questions remain to be explored, especially those regarding prevention and treatment.


Moore, Lorna Grindlay and Regensteiner, Judith G.
1983 Adaptation to High Altitude. Annual Review of Anthropology 12:285-304.