Science: Circulation for Altitude

In the 17th century a Spanish priest, Father Cob,. made an acute observation about the Indians of the high Andes. "The Indians," he wrote, "are red-blooded to an extreme degree, from whence they derive their excessive heat, as borne out by the fact that if in the time of greatest cold one touches their hand, one will always find heat in it, amazingly." In Natural History, Anthropologist Marschall T. Newman explains the physiological reasons for the Indians' "excessive heat."

Many of the Andean Indians, says Newman, live so high in the mountains that the air contains only two-thirds or one-half as much oxygen, volume for volume, as it does at sea level. To get enough oxygen for the heavy work they do, the Indians have conspicuous barrel chests and outsized lungs, but they also have subtler adaptations to altitude. The pockets in their lungs (alveoli) have more capillaries so that their blood can capture more oxygen from the thin air. A mountain Indian has about two quarts more blood than a sea-level person, and his red blood cells are bigger and more numerous. If he lives at three, miles altitude, he may have twice as much hemoglobin, the oxygen-carrying substance, as an ordinary person. His heart, which is 20% bigger than normal, pumps an extra-large stream of extra-rich blood, keeping his hands forever warm, as Father Cobo so accurately noted.