If we take all that district of Africa comprised between the Tropics, where the east wind blows most constantly, we shall easily conceive that the western coasts of this part of the world must, and actually do, experience a greater degree of heat than those of the eastern coasts; as the east wind reaches the latter with the freshness which it receives in passing over a vast sea, whereas before it reaches the former, it acquires a burning heat, in traversing the interior parts of Africa. Thus, therefore, the coasts of Senegal, Sierra Leona, Guinea, and all the western regions of Africa, situated under the Torrid Zone, are the hottest climates in the world; nor is it by any means so hot on the eastern coasts, at Mosambique, Mombaza, &c. I have not the smallest doubt, therefore, but this is the reason that we find the real negroes, or the blackest men, in the western territories of Africa, and Caffres, or black men, of a hue more light, in the eastern territories. The evident difference which subsists between these two species of blacks proceeds from the heat of their climate, which is not very great in the eastern, but excessive in the western. Beyond the Tropic, on the south, the heat is considerably diminished, not only from its situation as to climate, but from the point of Africa being contracted; and as that point is surrounded by the sea the air is necessarily more temperate than it could be in the middle of a continent. The colour of the inhabitants of this country begins to assume a fairer hue, and they are naturally more white than black. Nothing affords a more convincing proof that the climate is the principal cause of the variety in the human species than the colour of the Hottentots, who could not possibly be found less black did they not enjoy a more temperate climate.
In this opinion we shall be more confirmed if we examine the other nations under the Torrid Zone, on the east side of Africa. The inhabitants of the Maldivia islands, of Ceylon, of the point of the peninsula of India, of Sumatra, of Malacca, of Borneo, of Celebes, of the Philippines, &c. are very brown, though not absolutely black, from all these countries being either islands or peninsulas. In these climates the heat of the air is temporized by the sea; besides which, neither the east nor west wind, which reign alternately in that part of the globe, can reach the Indian Archipelago without passing over seas of an immense extent. As their heat is not excessive, therefore, all these islands are peopled with brown men; but in New Guinea we again meet with red blacks, and who, from the descriptions of travellers, seem to be absolute negroes, because the country they inhabit forms a continent to the east, and the wind is more hot than that which prevails in the Indian Ocean. In New Holland, where the heat of the climate is not so great, we find people less black, and not unlike the Hottentots. Do not these negroes and Hottentots, whom we meet with in the same latitude, and at so great a distance from the other negroes and Hottentots, evince their colour depends upon the heat of the climate? That there was ever any communication between Africa and this southern continent, it is impossible to suppose; and yet in both we find the same species of men, because the same circumstances occur which occasion the same degrees of heat.
From the animal creation we may obtain a further confirmation of what has been above advanced. In Dauphiny, it has been observed that all the hogs are black; and that on the other side of the Rhone, in Vivarais, where it is more cold than in Dauphiny, all the hogs are white. There is no probability that the inhabitants of one of these two provinces should have agreed to breed none but black hogs, and the other none but white ones. To me it appears, that this difference arises solely from the variation in the temperature of the climate, combined, perhaps, with that of the food of the animals.
The few blacks who have been found in the Philippines, and other islands of the Indian Ocean, seem to originate from the Papous, or Negroes of New Guinea, whom the Europeans have not known much longer than half a century. Dampier discovered the most eastern part in 1700, and gave it the name of New Britain; we are still ignorant of its extent, yet we know that, so far as has been discovered, it is not very populous.
In those climates alone, then, where circumstances combine to create a constant and excessive heat, do we meet with negroes. This heat is necessary not only to the production, but even to the preservation of negroes; and where the heat, though violent, is not comparable to that of Senegal, the negro infants are so susceptible of the impressions of the air, that there is a necessity for keeping them during the first nine days in warm apartments; if this precaution is omitted, and they are exposed to the air soon after their birth, a convulsion in the jaw succeeds, which preventing them from receiving any sustenance, they presently die.
In the History of the Academy of Sciences we read, that M. Littre, in dissecting a negro, in 1702, remarked, that the point of the glands which was not covered with the prepuce was black, and the rest perfectly white. From this observation it is evident, that the air is necessary to produce the blackness of negroes. Their children are born white, or rather red, like those of other men, but two or three days after they change to a tawny yellow, which gradually darkens till the seventh or eighth day, when they are completely black. All children two or three days after their birth have a kind of jaundice, which in white children is transitory, and leaves no impression upon the skin; but in negro children it gives a colour to the skin, and continues to grow more and more black. M. Kolbe mentions having observed this fact among the children of Hottentots. This jaundice, however, and the impression of the air, seem to be only occasional, and not the primary cause of this blackness; since it is remarked, that the children of negroes have, the instant of their birth, a blackness in the genitals, and at the root of the nails. The action of the air and the jaundice may serve to extend this blackness, but it is certain that the principle of it is communicated to the children by their parents; that in whatever country a negro may be born, he will be as black as if he had been brought forth in his own; and if there is any difference in the first generation it is imperceptible; from this circumstance, however, we are not to suppose, that after a certain number of generations, the colour would not undergo a very sensible change.
Many have been the researches of anatomists respecting this black colour. Some pretend, that it is neither in the skin, nor in the epidermis, but in the cellular membrane which is between them; that this membrane, though washed, and held ever so long in warm water, does not change colour, while the skin, and the surface of the skin, appear to be nearly as white as those of other men. Dr. Town, in his letter to the Royal Society, and a few others, maintain, that the blood is black in negroes, and from which cause their colour originates; a fact which I am inclined to believe, from having remarked, that among ourselves the blood of those who are tawny, yellow, or brown, is proportionally more black than that of others.
According to M. Barrere, this colour of the negroes is produced by the bile, which in them is not yellow, but always black as ink; of which he affirms he received certain proof from several negroes which he had occasion to dissect at Cayenne. When the bile is diffused, it tinges the skin of white people yellow; and it is probable, that if the former were black, the latter would be black also. But as when the overflow of the bile ceases, the skin recovers its natural whiteness, so on this principle there is a necessity for supposing that in the negroes there is always an overflow of bile, or at least that, as M. Barrere observes, it is so abundant, as naturally to secrete itself in the epidermis, in a quantity sufficient to communicate this black colour. It probable that the bile and blood of negroes are more brown than those of white men, as their skin is more black. But one of these facts can never be admitted as an explanation of the cause of the other; for if it is the blood or bile which, by its blackness, communicates this colour to the skin, then, instead of inquiring why the skin of negroes is black, we must inquire why their bile or blood is so; and thus, by deviating from the question, we find ourselves more than ever remote from the solution of it. For my own part, I own I have always been of opinion, that the cause which renders a Spaniard more brown than a Frenchman, and a Moor than a Spaniard, is also the cause which renders a Negro blacker than a Moor. At present I mean not to enquire how this cause acts, but only to ascertain that it does act, and that its effects are the more considerable, in proportion to the force and continuance of action.
Of the blackness of the skin, the principal cause is the heat of the climate. When this heat is excessive, as at Senegal, and in Guinea, the inhabitants are entirely black; when it is rather less violent, as on the eastern coasts of Africa, they are of a shade more light; when it becomes somewhat temperate, as in Barbary, Mogul, Arabia, &c. they are only brown; and in fine, when it is altogether temperate, as in Europe and in Asia, they are white; and the varieties there remarked proceed solely from the mode of living. All the Tartars, for example, are tawny, while the Europeans, who live in the same latitude, are white. This difference clearly arises from the former being always exposed to the air; having no towns nor fixed habitations; sleeping upon the earth, and living coarsely and savagely. These circumstances are sufficient to render them less white than the Europeans, who want nothing to render life comfortable and agreeable. Why are the Chinese whiter than the Tartars, whom they resemble in all their features? Certainly from the above reasons.
When cold becomes extreme, it produces effects similar to those of excessive heat. The Samoiedes, Laplanders, and Greenlanders, are very tawny; and it is even asserted, that some Greenlanders are as black as those of Africa. Here the two extremes meet. Violent cold and violent heat produce the same effect upon the skin, because these two causes act by a quality which they possess in common. Dryness of the air is this quality; and which cold is as equally productive as intense heat; by either the skin may be dried, and rendered as tawny as what we find it among the Laplanders. Cold compresses all the productions of nature; and thus it is that the Laplanders, who are perpetually exposed to the rigours of frost, are the smallest of the human species.