Human Male
A much more interesting fact, but one less easy to interpret, is
that the human male has, like the male ape, organs for suckling
the young. That there are real milk-glands, usually vestigial,
underneath the teats in the breast of the boy or the man is
proved by the many known cases in which men have suckled the
young. Several friends of the present writer have seen this done
in India and Ceylon by male "wet-nurses." As there is no tribe of
men or species of ape in which the male suckles the young
normally, we seem to be thrown back once more upon an earlier
ancestor. The difficulty is that we know of no mammal of which
both parents suckle the young, and some authorities think that
the breasts have been transferred to the male by a kind of
embryonic muddle. That is difficult to believe, as no other
feature has ever been similarly transferred to the opposite sex.
In any case the male breasts are vestigial organs. Another
peculiarity of the mammary system is that sometimes three, four,
or five pairs of breasts appear in a woman (and several have been
known even in a man). This is, apparently, an occasional
reminiscence of an early mammal ancestor which had large litters
of young and several pairs of breasts.
But there are features of the human body which recall an ancestor
even earlier than the quadruped. The most conspicuous of these is
the little fleshy pad at the inner corner of each eye. It is a
common feature in mammals, and is always useless. When, however,
we look lower down in the animal scale we find that fishes and
reptiles (and birds) have a third eyelid, which is drawn across
the eye from this corner. There is little room to doubt that the
little fleshy vestige in the mammal's eye is the shrunken
remainder of the lateral eyelid of a remote fish-ancestor.
A similar reminiscence is found in the pineal body, a small and
useless object, about the size and shape of a hazel-nut, in the
centre of the brain. When we examine the reptile we find a third
eye in the top of the head. The skin has closed over it, but the
skull is still, in many cases, perforated as it is for the eyes
in front. I have seen it standing out like a ball on the head of
a dead crocodile, and in the living tuatara--the very primitive
New Zealand lizard--it still has a retina and optic nerve. As the
only animal in nature to-day with an eye in this position (the
Pyrosome, a little marine animal of the sea-squirt family) is not
in the line of reptile and mammal ancestry, it is difficult to
locate the third eye definitely. 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.
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