CLIMATE AND RACE — COON 293 



wrist, and ankles. One centimeter of fat is given the same insulation 

 rating as a complete suit of winter clothing (Bazett, 1949, p. 145). 

 The healthy Negro living in a hot country carries almost no sub- 

 cutaneous fat. His superior performance in the desert, compared to 

 Whites of the same age and weight, has been demonstrated (Baker, 

 1953). 



In summary, adjustment to the cold requires large body mass, short 

 extremities, much fat, deep vein routing, a high basal metabolism, or 

 some combination of these five features. Adjustment to the heat re- 

 quires small body mass, attenuated extremities, little fat, extensive 

 superficial vein routing, a low basal metabolism, and a greater num- 

 ber of sweat glands per unit of surface area. Possibly the role of 

 melanin in starting the skin to sweat at a lower threshold by con- 

 version of UV to radiant heat may be added. Any combination of 

 these seven may be involved. The type or types of physique most 

 suited to cold resistance are exactly those which, the doctors tell us, 

 are most likely to suffer from heart trouble, and so it is a lucky thing 

 that adjustment to the cold does not place an extra load on the heart. 

 Heat-adapted physiques are those best calculated to stand the extra 

 heart load, which they receive. 



So far we have been thinking about heat loss from the skin, but 

 calories also leave the body through the lungs. In hot weather the 

 heat loss from the lungs through respiration is negligible and of 

 little help to the suffering organism, but as the mercury drops this 

 source of leakage becomes serious, reaching 50 kg. calories per 1,000 

 liters of expired air in extreme cold (Irving, 1951). Not only does 

 this affect the total heat load of the body, but it subjects the nasal 

 passages to heavy chilling. To what extent the Mongoloid face, 

 inside and out, may compensate for this by its special architecture 

 remains to be discovered. 



One other climatic hazard which human beings have faced and 

 overcome is that of reduced oxygen at high altitudes. Dill (1938) 

 and his associates have found that the inhabitants of the Andes have 

 become able to live and work at 17,500 feet and more, through the 

 fact that their blood carries a much higher concentration of red 

 corpuscles than of people at sea level. At the same time they need 

 more air, which they obtain through more efficient automatic breath- 

 ing control as well as the larger lungs. The requirements for physique 

 in high altitude resemble those for cold. Perhaps it is no coinci- 

 dence that the two great high-altitude plateaus of the world, the 

 Andean and the Tibetan, are inhabited by Mongoloid peoples who 

 greatly resemble each other. 



This paper does not pretend to cover, even in outline, all the more 

 obvious adaptive variations in man in the fields of color, size, and 



