The modern denizen of a suburban home with central heating and air conditioning probably has little idea of what thermodynamic feats the human body can demonstrate. While travelling in Tierra del Fuego on a bitterly cold winter’s day, Charles Darwin was astonished to see a woman, completely without clothing, nursing an infant and apparently untroubled by the cold sleet that was falling (Dibner, 1964). Geographers understand that the fires referred to in the name, Tierra del Fuego, are volcanic, and have nothing to do with the air temperature of that grand but inhospitable locale! Even today, there are societies in which people sleep exposed to the sky with little or no clothing, warmed if at all by small fires. The Australian aborigine and the Kalahari bushman are but two examples. Suffice it to say that intrepid scientists have demonstrated, by means of rectal thermometers, that the human body cools during such exposure, but extremes that would be lethal to a city dweller are tolerated as a matter of course among those who live under less temperate conditions.