The purpose of this website is to make available the findings of classic studies of high-altitude natives’ adaptation to hypoxia and to archive knowledge of the places, people, and data.

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Global Perspective

High altitude is conventionally defined as more than 2,000m because the effects on physiology become readily detectable. Many areas around the world are at 2,500m or above as indicated by this global map from NOAA (below).

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Introduction to the Science

Anthropologists and evolutionary biologists, physiologists and biomedical scientists share an intense interest in the biology of high altitude populations. Anthropologists and evolutionary biologists are curious about the processes of evolution and adaptation to an extreme, unavoidable environmental stress. Physiologists and biomedical scientists want to understand the processes engaged to maintain homeostasis under an extreme stress and hope to find clues to improve the treatment of patients at all altitudes.

 

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Who are high-altitude natives?

High-altitude natives are usually considered to be members of populations that have inhabited altitudes above ~ 3000m (10,000′) for thousands of years. The largest high-altitude native populations, those inhabiting the highest altitudes and the best studied are the Andean highlanders, the Aymara and the Quechua the Tibetans and their close relatives, the Sherpas. Smaller and less thoroughly studied high-altitude native populations are the Ethiopian highlanders, the Amharic and the Oromo the Kyrgyz.

 

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What is the stress at high altitude?

The primary stress at high altitude is hypoxia, less than the normal amount of oxygen in the air. It results from the progressively lower barometric pressure at higher altitudes. Oxygen comprises about 21% of the molecules in air at altitudes; however, because air becomes less dense, the number of air molecules in a volume decreases. This translates into fewer oxygen molecules in every breath of air and few to diffuse from the lungs into the bloodstream for delivery to the cells where it is used. The density of oxygen in a breath of air decreases progressively at higher altitudes. (See figure B.1)

At the Potala Palace in Lhasa, Tibet Autonomous Region at 3,658m, the oxygen density is about 68% that at sea level.

Another way to express this relationship is in terms of the partial pressure of inspired oxygen, PiO2. (See figure B.2) At 4,000m the PiO2 is just about 90 Torr (mmHg) as compared with about 150 Torr at sea level, i.e. 62% of the usual sea-level value.

This is the unavoidable, lifelong stress to which every man, woman, and child in a high-altitude native population experience. Other stresses are often found at high-altitude, including cold, aridity, wind, high ultraviolet radiation and low primary productivity.