As with the Himalayan mountains, the Andes impose severe conditions and many limitations on life. Consequently, Andean people are physically adapted to the heights in special ways. In contrast to persons born and raised at sea level, those living at Andean altitudes 2,500 meters or more above sea level have as much as 25 percent more blood that is more viscous and richer in red cells, a heart that is proportionately larger, and specially adapted, larger lungs, with an enhanced capacity to take in oxygen from the rare atmosphere. Biological adaptations have permitted the native highlanders to work efficiently and survive successfully in the Andean altitudes for 20,000 years.

The first important scientific research on high-altitude biology was undertaken by the Peruvian physician-scientist Carlos Monge Medrano in the 1920s. He showed that coca-leaf chewing played a role in aiding the metabolism in high-altitude populations. More recent studies have shown that coca chewing significantly aids in metabolizing high carbohydrate foods like potatoes, yucca, and corn, which are traditional staples in the Andean region, thus providing the chewer with more rapid energy input from his meals. Supposed narcotic effects of coca-leaf chewing are nil because enzymes in the mouth convert coca into atropine-like substances, unlike those involved in cocaine. Anthropologists Catherine Allen and Enrique Mayer have also demonstrated the central role traditional coca use plays in Andean communities as a medicine, ritual substance, and an element in economic and social affairs.

Data as of September 1992