196 Changing Human Nature 



migrating from a central region, and with the needs of 

 adaptation. It is only in such remote corners that the less 

 developed types could maintain themselves. This we infer 

 from considerations of climatic conditions, of the concomi- 

 tant food supply, and of competition with more highly de- 

 veloped types of later origin. 



There is a widely prevalent notion that man originated 

 in the tropics. This is on the theory that only in a genial cli- 

 mate and in the midst of abundant vegetation and game 

 could primitive man survive. Opposed to this view is the 

 fact that all races (those of the tropics as well as those of 

 the extremely cold regions) seem to be at their best in an 

 atmosphere corresponding to the temperate regions, that is, 

 at a mean temperature of about 60° to 70° Fahrenheit, and 

 in an atmosphere with varying relative humidity. Even the 

 equatorial negroes seem to be more healthy and more ener- 

 getic under such conditions than they are in their native 

 environment. 



The absence of hair is taken by some anthropologists to 

 indicate at least a very long sojourn of our ancestors in a 

 region that encouraged the use of clothing, probably the 

 skins of other animals. It is of course impossible to say 

 whether primitive man resorted to such external covering 

 after the loss of hair had made the additional protection nec- 

 essary, or whether he lost his own fur after he took to using 

 that of his neighbors. In either case there is implied a pro- 

 gressive adaptation, or the transmission of the effects of use 

 or disuse; and regarding this it is impossible to speak posi- 

 tively. It is interesting to note that tropical mammals that 

 have lost their hair have become characteristically thick- 

 skinned, as illustrated by the elephant, the hippopotamus 

 and the rhinoceros. These thickenings of the hide we assume 

 to represent a protective compensation, although again we 

 are entirely in the dark as to the mechanism by which such 

 change could have come about. At any rate, the fact that 

 rnan alone of the mammals has acquired a more tender skin 

 along with the loss of hair is taken to indicate that the use 



