Reactions to heat of aborigines and Caucasians

¹ Human Sciences Laboratory, Transvaal and Orange Free State Chamber of Mines, Johannesburg, South Africa, and School of Tropical Medicine and Hygiene, Sydney, Australia

A study was made of the physiological reactions to heat of samples of Australian aborigines and Australian Caucasians in the hot, humid tropics. Their results were then compared with those of unacclimatized and acclimatized Caucasians (South Africa). The Australian shows signs of a partial degree of acclimatization in that his heart rate and rectal temperature are lower and his sweat rate is higher than those of the unacclimatized South African Caucasian. The aborigine presents a less clear picture in that his rectal temperature is lower but his heart rate and sweat rate is the same as the unacclimatized Caucasian. A striking difference between the Caucasians and aborigines in Australia is the much higher sweat rates of the Caucasians. The lower sweat rates of the aborigine might result from the morphological feature of a greater surface area: mass ratio whereby he loses heat by radiation and convection more adequately than the Caucasian and therefore is able to conserve sweat; alternatively, he appears to have a more sensitively adjusted thermoregulatory control channel between rectal temperature and sweat rate.

Submitted on February 28, 1964