If a working ant or other neuter insect had been an ordinary animal, I
should have unhesitatingly assumed that all its characters had been slowly
acquired through natural selection; namely, by individuals having been born
with slight profitable modifications, which were inherited by the
offspring, and that these again varied and again were selected, and so
onwards. But with the working ant we have an insect differing greatly from
its parents, yet absolutely sterile; so that it could never have
transmitted successively acquired modifications of structure or instinct to
its progeny. It may well be asked how it is possible to reconcile this
case with the theory of natural selection?
First, let it be remembered that we have innumerable instances, both in our
domestic productions and in those in a state of nature, of all sorts of
differences of inherited structure which are correlated with certain ages
and with either sex. We have differences correlated not only with one sex,
but with that short period when the reproductive system is active, as in
the nuptial plumage of many birds, and in the hooked jaws of the male
salmon. We have even slight differences in the horns of different breeds
of cattle in relation to an artificially imperfect state of the male sex;
for oxen of certain breeds have longer horns than the oxen of other breeds,
relatively to the length of the horns in both the bulls and cows of these
same breeds.
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