The Origin of Species by Means of Natural Selection: Or, the Preservation of Favoured Races in the Struggle for Life, 6th EditionDarwin, Charles
History
The Origin of Species by Means of Natural Selection: Or, the Preservation of Favoured Races in the Struggle for Life, 6th Edition
Darwin, Charles
Evolution (Biology); Natural selection
All Mr. Mivart’s objections will be, or have been, considered in the
present volume. The one new point which appears to have struck many
readers is, “That natural selection is incompetent to account for the
incipient stages of useful structures.” This subject is intimately
connected with that of the gradation of the characters, often
accompanied by a change of function, for instance, the conversion of a
swim-bladder into lungs, points which were discussed in the last
chapter under two headings. Nevertheless, I will here consider in some
detail several of the cases advanced by Mr. Mivart, selecting those
which are the most illustrative, as want of space prevents me from
considering all.
The giraffe, by its lofty stature, much elongated neck, fore legs, head
and tongue, has its whole frame beautifully adapted for browsing on the
higher branches of trees. It can thus obtain food beyond the reach of
the other Ungulata or hoofed animals inhabiting the same country; and
this must be a great advantage to it during dearths. The Niata cattle
in South America show us how small a difference in structure may make,
during such periods, a great difference in preserving an animal’s life.
These cattle can browse as well as others on grass, but from the
projection of the lower jaw they cannot, during the often recurrent
droughts, browse on the twigs of trees, reeds, &c., to which food the
common cattle and horses are then driven; so that at these times the
Niatas perish, if not fed by their owners. Before coming to Mr.
Mivart’s objections, it may be well to explain once again how natural
selection will act in all ordinary cases. Man has modified some of his
animals, without necessarily having attended to special points of
structure, by simply preserving and breeding from the fleetest
individuals, as with the race-horse and greyhound, or as with the
game-cock, by breeding from the victorious birds. So under nature with
the nascent giraffe, the individuals which were the highest browsers
and were able during dearths to reach even an inch or two above the
others, will often have been preserved; for they will have roamed over
the whole country in search of food. That the individuals of the same
species often differ slightly in the relative lengths of all their
parts may be seen in many works of natural history, in which careful
measurements are given. These slight proportional differences, due to
the laws of growth and variation, are not of the slightest use or
importance to most species. But it will have been otherwise with the
nascent giraffe, considering its probable habits of life; for those
individuals which had some one part or several parts of their bodies
rather more elongated than usual, would generally have survived. These
will have intercrossed and left offspring, either inheriting the same
bodily peculiarities, or with a tendency to vary again in the same
manner; while the individuals less favoured in the same respects will
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