OCR Text |
Show 148 THE DESCENT OF MAN. PART I. cephalic; for instance, of two skulls of nearly equal breadth, the one from a wild rabbit and the other from a large domestic kind, the former was only 3·15 and the latter 4·3 inches in length.75 One of the most markerl distinctions in different races of man is that the skull in some is elongated, and in others rounded ; and here the explanation suggested by the case of the rabbits may partially hold good ; for vVelcker finds that short "men incline more to brachycephaly, and tall men to dolichocephaly; " 76 and tall men may be compared with the larger and longer-bodied rabbits, all of which have elongated skulls, or are dolichocephalic. From these several facts we can to a certain extent understand the means through which the great size and more or less rounded form of the skull has been acquired by man ; and these are characters eminently distinctive of him in comparison with the lower animals. Another most conspicuous difference between man and the lower animals is the nakedness of his skin. Whales and dolphins (Cetacea), dugongs (Sirenia) and the hippopotamus are naked; and this may be advantageous to them for gliding through the water ; nor would it be injurious 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 75 'Variation of Animals,' &c., vol. i. p. 117 on the elongation of the skull; p. 119, on the effect of the loppino- of one ear. 76 Quoted by Schaaffhausen, in 'Anthronaloo-. Review ' Oct. 1868 p. 41-9. .. , ' CHAP. IV. MANNER OF DEVELOPMENT. 149 their hairy covering from exposure to heat. This appears the more probable, as the elephants in India which live on elevated and cool districts are more hairy 77 than those on the lowlands. 1\Iay we then infer that man became divested of hair from having 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, favours 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 generally 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, altho:pgh 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 inclined to believe, as we shall see under sexual selection, that man, or rather primarily woman, became divested of hair for ornamental purposes; and according to this belief it is not 77 Owen, 'Anatomy of Vertebrates,' vol. iii. p. 619. 78 Isidore Geoffroy St.-Hilaire remarks (' Hist. Nat. Generale,' tom. ii. 1859, p. 215-217) on the head of man being covered with long hair; also on .the upper surfaces of monkeys and of other mammals being more thwkly clothed than the lower surfaces. This has likewise been ob.>erved by various authors. Prof. P. Gervais (' Hist. Nat. des Mammiferes,' tom. i. 1854, p. 28 ), however, states that in the Gorilla the hair is th~uner on the back, where it is partly rubbed off, tban on the lower suriacc. |