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However, the human body has both short-term and long-term adaptations to altitude that allow it to partially compensate for the lack of oxygen. There is a limit to the level of adaptation; mountaineers refer to the altitudes above 8,000 metres (26,000 ft) as the death zone, where it is generally believed that no human body can acclimatize.
High-altitude adaptation in humans is an instance of evolutionary modification in certain human populations, including those of Tibet in Asia, the Andes of the Americas, and Ethiopia in Africa, who have acquired the ability to survive at altitudes above 2,500 meters (8,200 ft). [1]
The Armstrong limit or Armstrong's line is a measure of altitude above which atmospheric pressure is sufficiently low that water boils at the normal temperature of the human body. Exposure to pressure below this limit results in a rapid loss of consciousness, followed by a series of changes to cardiovascular and neurological functions, and ...
Humans have survived for 2 years at 5,950 m (19,520 ft) [475 millibars (14.0 inHg; 6.89 psi) of atmospheric pressure], which appears to be near the limit of the permanently tolerable highest altitude. [13]
Human populations have developed agricultural production strategies to exploit varying characteristics of altitudinal zones. Elevation, climate, and soil fertility set upper limits on types of crops that can reside in each zone.
The adaptation of humans to high altitude is an example of natural selection in action. [2] 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 in EPAS1, but it has not been seen in Andean humans. [3]
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Altitude sickness, the mildest form being acute mountain sickness (AMS), is a harmful effect of high altitude, caused by rapid exposure to low amounts of oxygen at high elevation.