“From the presence of the woolly hair or lanugo on the human fœtus,
and of rudimentary hairs scattered over the body during maturity,”
Darwin inferred that “man is descended from some animal which was born
hairy and remained so during life.” He believed that “the loss of hair
is an inconvenience and probably an injury to man, even in a hot
climate, for he is thus exposed to the scorching in the sun, and to
sudden chills, especially during wet weather. As Mr. Wallace remarks,
the natives in all countries are glad to protect their naked backs and
shoulders with some slight covering. No one supposes that the nakedness
of the skin is any direct advantage to man; his body, therefore, cannot
have been divested of hair through Natural Selection.” Accordingly, he
concludes that man lost his hairy covering through Sexual Selection, for
ornamental purposes.
But if it can be shown that the nakedness of his skin _is_ in some way
of advantage to man, this argument falls to the ground. There are
sufficient reasons, I think, for believing that Natural Selection aided
Sexual Selection in divesting man of his hairy coat.
With his usual candour Darwin noticed the evidence which seemed to tell
against his view. Mr. Belt, he says, “believes that within the tropics
it is an advantage to man to be destitute of hair, as he is thus enabled
to free himself of the multitude of ticks (acari) and other parasites
with which he is often infested, and which sometimes cause ulceration.”
Darwin doubts, however, whether this evil is of sufficient magnitude to
have led to the denudation of the body through Natural Selection, “since
none of the many quadrupeds inhabiting the tropics have, as far as I
know, acquired any specialised means of relief.” But as primitive man’s
habits of cleanliness are much inferior to those of animals, this
objection loses its force; and it is, moreover, weakened by the
testimony of Sir W. Denison that “it is said to be a practice with the
Australians, when the vermin get troublesome, to singe themselves.” We
also know that the ancient Egyptians shaved off their hair from motives
of cleanliness.
However, it is not likely that the superior advantages of cleanliness
and freedom from parasites would alone have sufficed to produce so great
a change in man as the loss of his hair. It is more probable that the
sun was the chief agent in accomplishing this transformation. I fail to
see the force of Darwin’s contention that the fact that “the other
members of the order of Primates, to which man belongs, although
inhabiting various hot regions, are well clothed with hair, generally
thickest on the upper surface, is opposed to the supposition that man
became naked through the action of the sun.” For these animals commonly
live in forests and on trees, where they are protected from the rays of
the sun, which is not the case with man.
Furthermore, Darwin himself mentions some circumstances which point to
the conclusion that the sun is the cause of man’s nudity. He says, for
instance, that “elephants and rhinoceroses are almost hairless; and as
certain extinct species which formerly lived under an arctic climate
were covered with long wool or hair, it would almost appear as if the
existing species of both genera had lost their hairy covering from
exposure to heat. This appears the more probable as the elephants in
India which live on elevated and cool districts are more hairy than
those on the lowlands.”
Bearing in mind what was said in the chapter on the Complexion regarding
the negro’s skin, there is no difficulty in understanding why Natural
Selection should eliminate the hairy covering of the skin while
favouring a dark complexion. Hair not only absorbs the sun’s heat, but
retains that of the body; hence a hairy man not living on trees would be
very uncomfortable in Africa, and likely to succumb to the enervating
effects of high temperature. The negro’s naked skin, on the other hand,
is, as we have seen, specially devised as a _body-cooler_. The black
pigment protects the underlying nerves of temperature, while the solar
heat absorbed by this pigment is immediately radiated in the form of
perspiration. Now we can see not only why the negro’s skin is more
velvety, smooth, and hairless than our own, but why its sweat-pores are
larger and more numerous than in our skin.
At a later stage of evolution Sexual Selection probably came in to aid
in this process of denudation. We may infer this, in the first place,
from the analogous case of apes who have denuded and variously-coloured
patches on the head and elsewhere, which they use for purposes of
display, to attract the notice of the opposite sex; in the second place,
from the fact that there are not a few tribes who pluck out their hairs.
“The Fuegians threatened a young missionary, who was left for a time
with them, to strip him naked, and pluck the hairs from his face and
body, yet he was far from being a hairy man;” and “throughout the world
the races which are almost completely destitute of a beard, dislike
hairs on the face and body, and take pains to eradicate them.” Darwin
also notes some facts which, by analogy, seem to make it probable that
“the long-continued habit of eradicating the hair may have produced an
inherited effect.”
In the case of the white race we cannot rely so much on the action of
the sun as accounting for the absence of hair, but must place more
especial emphasis on Sexual Selection. We are warranted in doing this by
the consideration that Taste for Beauty is more developed in the white
race, and therefore has more influence in controlling the choice of a
mate. “As the body in woman is less hairy than in man, and as this
character is common to all races, we may conclude” with Darwin “that it
was our female semi-human ancestors who were first divested of hair,”
this character being then transmitted by the mothers to their children
of both sexes.
The two universal traits of Beauty which chiefly guided man in the
preference of a hairless skin were evidently Smoothness and Colour. One
need only compare for a moment the face of a female chimpanzee, its
leathery folded skin and straggling hairs, with the smooth and rosy
complexion of a European damsel, to understand that, leaving touch out
of consideration, sight alone would have sufficed to give the preference
to the hairless skin. But since we derive less direct advantage than the
tropical races from such a skin, cases of reversion to the hairy type
are more common among us than with them, and our bodies in general are
more hairy.