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Descent of Man [ 1871]

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Author Topic: Descent of Man [ 1871]  (Read 6372 times)
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« Reply #210 on: February 10, 2009, 03:10:06 pm »

With respect to the origin of the habit, von Fischer remarks that
his monkeys like to have their naked hinder ends patted or stroked,
and that they then grunt with pleasure. They often also turn this part
of their bodies to other monkeys to have bits of dirt picked off,
and so no doubt it would be with respect to thorns. But the habit with
adult animals is connected to a certain extent with sexual feelings,
for von Fischer watched through a glass door a female Cynopithecus
niger, and she during several days, "umdrehte und dem Mannchen mit
gurgelnden Tonen die stark gerothete Sitzflache zeigte, was ich fruher
nie an diesem Thier bemerkt hatte. Beim Anblick dieses Gegenstandes
erregte sich das Mannchen sichtlich, denn es polterte heftig an den
Staben, ebenfalls gurgelnde Laute ausstossend." As all the monkeys
which have the hinder parts of their bodies more or less brightly
coloured live, according to von Fischer, in open rocky places, he
thinks that these colours serve to render one sex conspicuous at a
distance to the other; but, as monkeys are such gregarious animals,
I should have thought that there was no need for the sexes to
recognise each other at a distance. It seems to me more probable
that the bright colours, whether on the face or hinder end, or, as
in the mandrill, on both, serve as a sexual ornament and attraction.
Anyhow, as we now know that monkeys have the habit of turning their
hinder ends towards other monkeys, it ceases to be at all surprising
that it should have been this part of their bodies which has been more
or less decorated. The fact that it is only the monkeys thus
characterised which, as far as at present known, act in this manner as
a greeting towards other monkeys renders it doubtful whether the habit
was first acquired from some independent cause, and that afterwards
the parts in question were coloured as a sexual ornament; or whether
the colouring and the habit of turning round were first acquired
through variation and sexual selection, and that afterwards the
habit was retained as a sign of pleasure or as a greeting, through the
principle of inherited association. This principle apparently comes
into play on many occasions: thus it is generally admitted that the
songs of birds serve mainly as an attraction during the season of
love, and that the leks, or great congregations of the black-grouse,
are connected with their courtship; but the habit of singing has
been retained by some birds when they feel happy, for instance by
the common robin, and the habit of congregating has been retained by
the black-grouse during other seasons of the year.
  I beg leave to refer to one other point in relation to sexual
selection. It has been objected that this form of selection, as far as
the ornaments of the males are concerned, implies that all females
within the same district must possess and exercise exactly the same
taste. It should, however, be observed, in the first place, that
although the range of variation of a species may be very large, it
is by no means indefinite. I have elsewhere given a good instance of
this fact in the pigeon, of which there are at least a hundred
varieties differing widely in their colours, and at least a score of
varieties of the fowl differing in the same kind of way; but the range
of colour in these two species is extremely distinct. Therefore the
females of natural species cannot have an unlimited scope for their
taste. In the second place, I presume that no supporter of the
principle of sexual selection believes that the females select
particular points of beauty in the males; they are merely excited or
attracted in a greater degree by one male than by another, and this
seems often to depend, especially with birds, on brilliant
colouring. Even man, excepting perhaps an artist, does not analyse the
slight differences in the features of the woman whom he may admire, on
which her beauty depends. The male mandrill has not only the hinder
end of his body, but his face gorgeously coloured and marked with
oblique ridges, a yellow beard, and other ornaments. We may infer from
what we see of the variation of animals under domestication, that
the above several ornaments of the mandrill were gradually acquired by
one individual varying a little in one way, and another individual
in another way. The males which were the handsomest or the most
attractive in any manner to the females would pair oftenest, and would
leave rather more offspring than other males. The offspring of the
former, although variously intercrossed, would either inherit the
peculiarities of their fathers or transmit an increased tendency to
vary in the same manner. Consequently the whole body of males
inhabiting the same country would tend from the effects of constant
intercrossing to become modified almost uniformly, but sometimes a
little more in one character and sometimes in another, though at an
extremely slow rate; all ultimately being thus rendered more
attractive to the females. The process is like that which I have
called unconscious selection by man, and of which I have given several
instances. In one country the inhabitants value a fleet or light dog
or horse, and in another country a heavier and more powerful one; in
neither country is there any selection of individual animals with
lighter or stronger bodies and limbs; nevertheless after a
considerable lapse of time the individuals are found to have been
modified in the desired manner almost uniformly, though differently in
each country. In two absolutely distinct countries inhabited by the
same species, the individuals of which can never during long ages have
intermigrated and intercrossed, and where, moreover, the variations
will probably not have been identically the same, sexual selection
might cause the males to differ. Nor does the belief appear to me
altogether fanciful that two sets of females, surrounded by a very
different environment, would be apt to acquire somewhat different
tastes with respect to form, sound, or colour. However this may be,
I have given in my Descent of Man instances of closely-allied birds
inhabiting distinct countries, of which the young and the females
cannot be distinguished, whilst the adult males differ considerably,
and this may be attributed with much probability to the action of
sexual selection.

                         THE END

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