Chap. IV.] MANNER OF DEVELOPMENT. 143 



jurious to them from the loss of warmth, as the species 

 which inhabit the colder regions are protected by a thick 

 layer of blubber, serving the same purpose as the fur of 

 seals and otters. Elephants and rhinoceroses are almost 

 hairless; and, as certain extinct species which formerly 

 lived under an arctic climate were covered with long wool 

 or hair, it would almost appear as if the existing species 

 of both genera had lost their hairy covering from expos- 

 ure to heat. This appears the more probable, as the 

 elephants in India which live on elevated and cool dis- 

 tricts are more hairy " than those on the lowlands. May 

 we then infer that man became divested of hair from hav- 

 ing aboriginally inhabited some tropical land ? The fact 

 of the hair being chiefly retained in the male sex on the 

 chest and face, and in both sexes at the junction of all 

 four limbs with the trunk, favors this inference, assuming 

 that the hair was lost before man became erect ; for the 

 parts which now retain most hair would then have been 

 most protected from the heat of the sun. The crown of 

 the head, however, offers a curious exception, for at all 

 times it must have been one of the most exposed parts, 

 yet it is thickly clothed with hair. In this respect man 

 agrees with the great majority of quadrupeds, which gen- 

 erally have their upper and exposed surfaces more thickly 

 clothed than the lower surface. Nevertheless, the fact 

 that the other members of the order of Primates, to which 

 man belongs, although inhabiting various hot regions, are 

 well clothed with hair, generally thickest on the upper 

 surface, 78 is strongly opposed to the supposition that man 

 became naked through the action, of the sun. I am in- 



" Owen, 'Anatomy of Vertebrates,' vol. iii. p. G19. 



73 Isidore Geoffroy St.-Hilaire remarks ('Hist. Nat. Generale,' torn, 

 ii 1859, pp. 215-21*7) on the head of man being covered with long hair; 

 also on the upper surfaces of monkeys and of other mammals being moro 

 thickly clothed than the lower surfaces. This has likewise been ob- 



