Doubtless there is some truth in Darwin’s view, but it does not cover the whole ground. Natural as well as Sexual Selection has been instrumental in producing the diverse colours of various races. Hitherto the trouble has been that no one could understand how a black skin could be useful to an African negro. It ought to make him feel uncomfortably hot—for is it not well known that black absorbs heat more than any other colour? and do we not feel warmer in summer if we wear black than if we wear white clothes?
No doubt whatever. But it so happens that the skin is not made of dead wool or felt. It contains, among various other ingenious arrangements, a vast number of minute holes or pores, through which, when we are very warm, the perspiration leaks, and, in changing into vapour, absorbs the body’s heat and leaves it cool, or even cold. Now, in a negro’s skin these pores are both larger and more numerous than in ours, which partly accounts for his indifference to heat, and the fact that his temperature is lower than ours. Yet it does not solve the problem in hand; for there is no visible reason why Natural Selection should not succeed in enlarging the number and size of the pores in a white skin as easily as in a black one.
A year or two ago Surgeon-Major Alcock sent a communication to Nature in which, as I believe, he for the first time suggested the true reason why tropical man is black, and why his blackness is useful to him. He pointed out that since the pigment-cells in the negro’s skin are placed in front of the nerve terminations, they serve to lessen the intensity of the nerve vibrations that would be caused in a naked human body by exposure to a tropical sun; so that the pigment plays the same part as a piece of smoked glass held between the sun and the eyes.
This ingenious theory at once explains some curious and apparently anomalous observations communicated to Nature by Mr. Ralph Abercrombie from Darjeeling. They are that “In Morocco, and all along the north of Africa, the inhabitants blacken themselves round the eyes to avert ophthalmia from the glare off hot sand;” that “In Fiji the natives, who are in the habit of painting their faces with red and white stripes as an ornament, invariably blacken them when they go out fishing on the reef in the full glare of the sun;” and that “In the Sikkim hills the natives blacken themselves round the eyes with charcoal to palliate the glare of a tropical sun on newly-fallen snow.”
How, on the other hand, are we to account for the white complexion of northern races? It is well known that there is a tendency among arctic animals to become white. This, in many cases, can be accounted for by the advantage white beasts of prey, as well as their victims, thus gain in escaping detection. But it is probable that another agency comes into play, first suggested by Craven in 1846, and thus summarised by a writer in Nature, 2d April 1885: “It is well known that white, as the worst absorber, is also the worst radiator of all forms of radiant energy, so that warm-blooded creatures thus clad would be better enabled to withstand the severity of an arctic climate—the loss of heat by radiation might, in fact, be expected to be less rapid than if the hairs or feathers were of a darker colour.”
This argument, which may be applied to man as well as to animals, is greatly strengthened by a circumstance which at first appears to oppose it—the fact, namely, that insects in northern regions, instead of being light-coloured, show a tendency toward blackness. But this apparent anomaly is easily explained. Insects, being cold-blooded, cannot lose any bodily heat through radiation; whereas a black surface, by absorbing as much solar heat as possible while it lasts, adds to their comfort and vitality.
The question now arises, Which was the original colour of the human race, white or black? This question, too, we are enabled to answer with the aid of a principle of evolution which, so far, has stood every test,—the principle that the child’s development is an epitome of the evolution of his race. Before birth there is no colouring matter at all in the skin of a negro child. “In a new-born child the colour is light gray, and in the northern parts of the negro countries the completely dark colour is not attained till towards the third year,” says Waitz; and again, in speaking of Tahiti: “The children are here (as everywhere in Polynesia) white at birth, and only gradually assume their darker colour under the influence of sunlight; covered portions of their bodies remain lighter, and since women wear more clothes than men, and dwell more in the shade, they too are often of so light a colour that they have red cheeks and blush visibly.”
So we are entitled to infer that primitive man was originally white, or whitish. As he moved south, Natural Selection made him darker and darker by continually favouring the survival of those individuals whose colour—owing to the spontaneous variation found throughout Nature—was of a dark shade, and therefore better able to dull the ardour of the sun’s rays. In the north, on the contrary, a light complexion was favoured for its quality of retaining the body’s heat. The yellow and red varieties need not be specially considered, for it has been shown that the different tints of the iris are merely due to the greater or less quantity of the same pigmentary matter; and as the colouring matter of the complexion and the hair is similar to that of the eye, it is probable that the same holds true of different hues of the skin; so that yellowish, brown, and reddish tints may be looked upon as mere intermediate stages between white and black. A trace of pigment, indeed, is found even in our skins; and I believe that the reason why we become brown on exposure to the sun is that the skin, when thus exposed and irritated, secretes a larger amount of this colouring matter, to serve, like a dimly-smoked glass, as a protection against scorching rays.
From all these considerations we may safely infer that the particular hue of man’s skin in each climate is useful to him, and not merely an ornamental product of “taste,” as Darwin believed. Yet to some extent Sexual Selection, doubtless, does come into play in most cases. At a low stage of culture each race likes its special characteristics in an exaggerated form,—a trait which would lead the more vigorous men to persistently select the darkest girls as wives, and thus cause their gradual predominance over the others: while the men, too, would, of course, inherit a darker tint from their mothers. But a still more important consideration is this, that, as Dr. Topinard points out, “Dark colour in the negro is a sign of health,”—naturally, since the darker the dermal pigment, the better are the nerves of temperature protected against the enervating solar rays. Concerning the Polynesians, too, Ellis (cited by Waitz) “notes expressly that a dark colour was more admired and desired because it was looked upon as a sign of vigour.”
These facts yield us a most profound insight into the methods of amorous selection. The erotic instinct, whose duty is the preservation of the species, is above all things attracted by Health, because without Health the species must languish and die out. In a climate where—under the circumstances in which negroes live—a light complexion is incompatible with Health, it is bound to be eliminated.