CLIMATE AND RACE — COON 285 



miles? The answer, which is geographical, confirms our interpreta- 

 tion of black skins in the Old World. The coast of Ecuador is heavily 

 forested. Open country begins at the Peruvian border, 4° south of 

 the Equator, whence it continues to the forest zone of Chile. The 

 coastal desert averages only 20 miles wide. Owing to the combina- 

 tion of the mountains behind and the cold Humboldt Current in front, 

 the air is cool, the humidity high, the sky usually overcast, and little 

 solar radiation gets through. Moving up into the highlands, we 

 should expect a double concentration of UV at 10,000 feet, where one- 

 sixth more solar radiation penetrates the atmosphere than at sea level. 

 However, the region of Quito, which is on the Equator, is frequently 

 cloudy ; the year has two rainy peaks. Thunder, Brooks says (1930) , 

 is heard on 99 days each year. Since the air is also cold, the Indians 

 cover up as much of their skin as possible. At 17° farther south, 

 on the shores of Lake Titicaca, less rain and clouds appear, but the 

 humidity is moderately high. Americans with untannable blond 

 skins suffer intensely. The Indians, who wear broad-brimmed hats 

 as well as the usual heavy clothing, tan to a deep reddish brown on 

 exposed parts. 



Moving eastward we find most of the Amazonian countryside heav- 

 ily forested. Indians, Negroes, Wliites, and all shades between get 

 along with equal ease as far as UV is concerned. However, between 

 the great river system in Brazil, the Guianas, and Venezuela are patches 

 of savannah, precisely the kind of country in which black-skinned ani- 

 mals and men luxuriate in Africa. However, these patches are small 

 and not long ago may have been smaller. They support no tempt- 

 ing animal life as in Africa, and the few Indians who go out there are 

 refugees from the forests that line the streams. There is no evidence 

 of any earlier population in this region at all. From all these con- 

 siderations no reason appears for a black-skinned population to have 

 developed in the Americas. The relative antiquity of man in the 

 two hemispheres is therefore beside the point. 



While Gloger's rule appears to cover variations in the response 

 of the human skin to UV, both Bergmann's and Allen's rules are cut 

 to fit the other end of the scale, radiant heat. Unlike UV, radiant 

 heat both enters and leaves the body, which is physiologically well 

 adapted to maintain an even temperature under extreme environ- 

 mental conditions. Clothing, shelter, and fire also help, but not to 

 the exclusion of physiological adaptation. 



Bergmann's rule, that warm-blooded animals of a given polytypic 

 species will be larger in the colder and smaller in the warmer portions 

 of its ecological range, is based on the physical fact that the larger 

 a body, all else, including shape, being equal, the smaller the ratio 

 of skin surface area to bulk, one being a square, and the other a cube. 



