the large beard of the male orang, may protect their throats when
fighting; for the keepers in the Zoological Gardens inform me that many
monkeys attack each other by the throat; but it is not probable that
the beard has been developed for a distinct purpose from that served by
the whiskers, moustache, and other tufts of hair on the face; and no
one will suppose that these are useful as a protection. Must we
attribute all these appendages of hair or skin to mere purposeless
variability in the male? It cannot be denied that this is possible; for
in many domesticated quadrupeds, certain characters, apparently not
derived through reversion from any wild parent form, are confined to
the males, or are more developed in them than in the females for
instance, the hump on the male zebu-cattle of India, the tail of
fat-tailed rams, the arched outline of the forehead in the males of
several breeds of sheep, and lastly, the mane, the long hairs on the
hind legs, and the dewlap of the male of the Berbura goat. (18. See the
chapters on these several animals in vol. i. of my Variation of
Animals under Domestication; also vol. ii. p. 73; also chap. xx. on
the practice of selection by semi-civilised people. For the Berbura
goat, see Dr. Gray, Catalogue, ibid. p. 157.) The mane, which occurs
only in the rams of an African breed of sheep, is a true secondary
sexual character, for, as I hear from Mr. Winwood Reade, it is not
developed if the animal be castrated. Although we ought to be extremely
cautious, as shewn in my work on Variation under Domestication, in
concluding that any character, even with animals kept by semi-civilised
people, has not been subjected to selection by man, and thus augmented,
yet in the cases just specified this is improbable; more especially as
the characters are confined to the males, or are more strongly
developed in them than in the females. If it were positively known that
the above African ram is a descendant of the same primitive stock as
the other breeds of sheep, and if the Berbura male-goat with his mane,
dewlap, etc., is descended from the same stock as other goats, then,
assuming that selection has not been applied to these characters, they
must be due to simple variability, together with sexually-limited
inheritance.
Hence it appears reasonable to extend this same view to all analogous
cases with animals in a state of nature. Nevertheless I cannot persuade
myself that it generally holds good, as in the case of the
extraordinary development of hair on the throat and fore-legs of the
male Ammotragus, or in that of the immense beard of the male Pithecia.
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