If numerous species, belonging to the same
genera or families, have really started into life all at once, the
fact would be fatal to the theory of descent with slow modification
through natural selection. For the development of a group of forms,
all of which have descended from some one progenitor, must have been
an extremely slow process; and the progenitors must have lived long
ages before their modified descendants. But we continually over-rate
the perfection of the geological record, and falsely infer, because
certain genera or families have not been found beneath a certain
stage, that they did not exist before that stage. We continually
forget how large the world is, compared with the area over which our
geological formations have been carefully examined; we forget that
groups of species may elsewhere have long existed and have slowly
multiplied before they invaded the ancient archipelagoes of Europe and
of the United States. We do not make due allowance for the enormous
intervals of time, which have probably elapsed between our consecutive
formations,--longer perhaps in some cases than the time required for
the accumulation of each formation. These intervals will have given
time for the multiplication of species from some one or some few
parent-forms; and in the succeeding formation such species will appear
as if suddenly created.
I may here recall a remark formerly made, namely that it might require
a long succession of ages to adapt an organism to some new and
peculiar line of life, for instance to fly through the air; but that
when this had been effected, and a few species had thus acquired a
great advantage over other organisms, a comparatively short time would
be necessary to produce many divergent forms, which would be able to
spread rapidly and widely throughout the world.
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