body. Now I was at first much surprised on finding that in all these
rabbits the skull had become elongated or dolichocephalic; 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 3.15
and the latter 4.3 inches in length. (85. Variation of Animals and
Plants under Domestication, vol. i. p. 117, on the elongation of the
skull; p. 119, on the effect of the lopping of one ear.) One of the
most marked distinctions in different races of men is that the skull in
some is elongated, and in others rounded; and here the explanation
suggested by the case of the rabbits may hold good; for Welcker finds
that short men incline more to brachycephaly, and tall men to
dolichocephaly (86. Quoted by Schaaffhausen, in Anthropological
Review, Oct. 1868, p. 419.); 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 understand, to a certain extent, the
means by which the great size and more or less rounded form of the
skull have 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 porpoises (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 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 (87. Owen, Anatomy of Vertebrates, vol. iii. p. 619.) than
those on the lowlands. May we then infer that man became divested of
hair from having aboriginally inhabited some tropical land? That the
hair is 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 on the assumption that the hair was lost before man
became erect; for the parts which now retain most hair would then have
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