But when we find the skin
closing over it in the amphibian and reptile, then the bone, and
then see it gradually atrophying and being buried under the
growing brain, we must refer it to some early fish-ancestor. This
ancestor, we may recall, is also reflected for a time in the
gill-slits and arches, with their corresponding fish-like heart
and blood-vessels, during man's embryonic development, as we saw
in a former chapter.
These are only a few of the more conspicuous instances of
vestigial structures in man. Metchnikoff describes about a
hundred of them. Even if there were no remains of primitive man
pointing in the direction of a common ancestry with the ape, no
lower types of men in existence with the same tendency, no apes
found in nature to-day with a structure so strikingly similar to
that of man, and no fossil records telling of the divergence of
forms from primitive groups in past time, we should be forced to
postulate the evolution of man in order to explain his actual
features. The vestigial structures must be interpreted as we
interpret the buttons on the back of a man's coat. They are
useless reminiscences of an age in which they were useful.
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