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Descent of Man [ 1871]

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Author Topic: Descent of Man [ 1871]  (Read 2863 times)
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« Reply #210 on: February 10, 2009, 03:08:12 pm »

 * The Rev. J. A. Picton gives a discussion to this effect in his New
Theories and the Old Faith, 1870.

  I am aware that the conclusions arrived at in this work will be
denounced by some as highly irreligious; but he who denounces them
is bound to shew why it is more irreligious to explain the origin of
man as a distinct species by descent from some lower form, through the
laws of variation and natural selection, than to explain the birth
of the individual through the laws of ordinary reproduction. The birth
both of the species and of the individual are equally parts of that
grand sequence of events, which our minds refuse to accept as the
result of blind chance. The understanding revolts at such a
conclusion, whether or not we are able to believe that every slight
variation of structure,- the union of each pair in marriage, the
dissemination of each seed,- and other such events, have all been
ordained for some special purpose.

  Sexual selection has been treated at great length in this work; for,
as I have attempted to shew, it has played an important part in the
history of the organic world. I am aware that much remains doubtful,
but I have endeavoured to give a fair view of the whole case. In the
lower divisions of the animal kingdom, sexual selection seems to
have done nothing: such animals are often affixed for life to the same
spot, or have the sexes combined in the same individual, or what is
still more important, their perceptive and intellectual faculties
are not sufficiently advanced to allow of the feelings of love and
jealousy, or of the exertion of choice. When, however, we come to
the Arthropoda and Vertebrata, even to the lowest classes in these two
great sub-kingdoms, sexual selection has effected much.
  In the several great classes of the animal kingdom,- in mammals,
birds, reptiles, fishes, insects, and even crustaceans,- the
differences between the sexes follow nearly the same rules. The
males are almost always the wooers; and they alone are armed with
special weapons for fighting with their rivals. They are generally
stronger and larger than the females, and are endowed with the
requisite qualities of courage and pugnacity. They are provided,
either exclusively or in a much higher degree than the females, with
organs for vocal or instrumental music, and with odoriferous glands.
They are ornamental with infinitely diversified appendages, and with
the most brilliant or conspicuous colours, often arranged in elegant
patterns, whilst the females are unadorned. When the sexes differ in
more important structures, it is the male which is provided with
special sense-organs for discovering the female, with locomotive
organs for reaching her, and often with prehensile organs for
holding her. These various structures for charming or securing the
female are often developed in the male during only part of the year,
namely the breeding-season. They have in many cases been more or
less transferred to the females; and in the latter case they often
appear in her as mere rudiments. They are lost or never gained by
the males after emasculation. Generally they are not developed in
the male during early youth, but appear a short time before the age
for reproduction. Hence in most cases the young of both sexes resemble
each other; and the female somewhat resembles her young offspring
throughout life. In almost every great class a few anomalous cases
occur, where there has been an almost complete transposition of the
characters proper to the two sexes; the females assuming characters
which properly belong to the males. This surprising uniformity in
the laws regulating the differences between the sexes in so many and
such widely separated classes, is intelligible if we admit the
action of one common cause, namely sexual selection.
  Sexual selection depends on the success of certain individuals
over others of the same sex, in relation to the propagation of the
species; whilst natural selection depends on the success of both
sexes, at all ages, in relation to the general conditions of life. The
sexual struggle is of two kinds; in the one it is between
individuals of the same sex, generally the males, in order to drive
away or kill their rivals, the females remaining passive; whilst in
the other, the struggle is likewise between the individuals of the
same sex, in order to excite or charm those of the opposite sex,
generally the females, which no longer remain passive, but select
the more agreeable partners. This latter kind of selection is
closely analogous to that which man unintentionally, yet
effectually, brings to bear on his domesticated productions, when he
preserves during a long period the most pleasing or useful
individuals, without any wish to modify the breed.
  The laws of inheritance determine whether characters gained
through sexual selection by either sex shall be transmitted to the
same sex, or to both; as well as the age at which they shall be
developed. It appears that variations arising late in life are
commonly transmitted to one and the same sex. Variability is the
necessary basis for the action of selection, and is wholly independent
of it. It follows from this, that variations of the same general
nature have often been taken advantage of and accumulated through
sexual selection in relation to the propagation of the species, as
well as through natural selection in relation to the general

purposes of life. Hence secondary sexual characters, when equally
transmitted to both sexes can be distinguished from ordinary
specific characters only by the light of analogy. The modifications
acquired through sexual selection are often so strongly pronounced
that the two sexes have frequently been ranked as distinct species, or
even as distinct genera. Such strongly-marked differences must be in
some manner highly important; and we know that they have been acquired
in some instances at the cost not only of inconvenience, but of
exposure to actual danger.
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