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Descent of Man [ 1871]

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Author Topic: Descent of Man [ 1871]  (Read 2889 times)
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« Reply #180 on: February 10, 2009, 01:23:27 pm »

* Dr. Gray, Gleanings from the Menagerie at Knowsley, pl. 28.
  *(2) Judge Caton on the wapiti, Transact. Ottawa Acad. Nat.
Sciences, 1868, pp. 36, 40; Blyth, Land and Water, on Capra aegagrus
1867, p. 37.

 Male quadrupeds of many kinds differ from the females in having
more hair, or hair of a different character, on certain parts of their
faces. Thus the bull alone has curled hair on the forehead.* In
three closely-allied
sub-genera of the goat family, only the males possess beards sometimes
of large size; in two other sub-genera both sexes have a beard, but it
disappears in some of the domestic breeds of the common goat; and
neither sex of the Hemitragus has a beard. In the ibex the beard is
not developed during the summer, and it is so small at other times
that it may be called rudimentary.*(2) With some monkeys the beard
is confined to the male, as in the orang; or is much larger in the
male than in the female, as in the Mycetes caraya and Pithecia satanas
(see fig. 68). So it is with the whiskers of some species of
Macacus,*(3) and, as we have seen, with the manes of some species of
baboons. But with most kinds of monkeys the various tufts of hair
about the face and head are alike in both sexes.

  * Hunter's Essays and Observations, edited by Owen, 1861. vol. i.,
p. 236.
  *(2) See Dr. Gray's Catalogue of Mammalia in the British Museum,
part iii., 1852, p. 144.
  *(3) Rengger, Saugthiere, &c., s. 14; Desmarest, Mammalogie, p. 86.

  The males of various members of the ox family (Bovidae), and of
certain antelopes, are furnished with a dewlap, or great fold of
skin on the neck, which is much less developed in the female.
  Now, what must we conclude with respect to such sexual differences
as these? No one will pretend that the beards of certain male goats,
or the dewlaps of the bull, or the crests of hair along the backs of
certain male antelopes, are of any use to them in their ordinary
habits. It is possible that the immense beard of the male Pithecia,
and 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.* 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, &c., 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

  * 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 Berbuar goat, see Dr. Gray, Catalogue, ibid., p. 157.

  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. Such study as I have been able to give to nature makes me
believe that parts or organs which are highly developed, were acquired
at some period for a special purpose. With those antelopes in which
the adult male is more strongly-coloured than the female, and with
those monkeys in which the hair on the face is elegantly arranged
and coloured in a diversified manner, it seems probable that the
crests and tufts of hair were gained as ornaments; and this I know
is the opinion of some naturalists. If this be correct, there can be
little doubt that they were gained or at least modified through sexual
selection; but how far the same view may be extended to other
mammals is doubtful.

  Colour of the Hair and of the Naked Skin.- I will first give briefly
all the cases known to me of male quadrupeds differing in colour
from the females. With marsupials, as I am informed by Mr. Gould,
the sexes rarely differ in this respect; but the great red kangaroo
offers a striking exception, "delicate blue being the prevailing
tint in those parts of the female which in the male are red."* In
the Didelphis opossum of Cayenne the female is said to be a little
more red than the male. Of the rodents, Dr. Gray remarks: "African
squirrels, especially those found in the tropical regions, have the
fur much brighter and more vivid at some seasons of the year than at
others, and the fur of the male is generally brighter than that of the
female."*(2) Dr. Gray informs me that he specified the African
squirrels, because, from their unusually bright colours, they best
exhibit this difference. The female of the Mus minutus of Russia is of
a paler and dirtier tint than the male. In a large number of bats
the fur of the male is lighter than in the female.*(3) Mr. Dobson also
remarks, with respect to these animals: "Differences, depending partly
or entirely on the possession by the male of fur of a much more
brilliant hue, or distinguished by different markings or by the
greater length of certain portions, are met only, to any appreciable
extent, in the frugivorous bats in which the sense of sight is well
developed." This last remark deserves attention, as bearing on the
question whether bright colours are serviceable to male animals from
being ornamental. In one genus of sloths, it is now established, as
Dr. Gray states, "that the males are ornamented differently from the
females- that is to say, that they have a patch of soft short hair
between the shoulders, which is generally of a more or less orange
colour, and in one species pure white. The females, on the contrary,
are destitute of this mark."
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