Thus favorable variations tend to
increase and become more marked from generation to generation.
Now it has always been known that breeders could produce a race of
markedly peculiar form or characteristics by selecting the
individuals possessing this quality in the highest degree and
breeding only from these. The breeder depends upon heredity,
variation, and his selection of the individuals from which to breed.
Similarly in nature new species have arisen through heredity,
variation, and a selection according to the laws of nature of those
varying in conformity with their environment. And this Mr. Darwin
called natural, in contrast with the breeder's artificial,
"selection," arising from the "struggle for existence," and
resulting in what Mr. Spencer has called the "survival of the
fittest."
Let us take a single illustration. Many of the species of beetles on
oceanic islands have very rudimentary wings, or none at all, and yet
their nearest relatives are winged forms on some neighboring
continent. Mr. Darwin would explain the origin of these evidently
distinct wingless species as follows: They are descended from winged
ancestors blown or otherwise transported thither from the
neighboring continent. But beetles are slow and clumsy fliers, and
on these wind-swept islands those which flew most would be blown out
to sea and drowned.
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