Popular Science Monthly/Volume 17/May 1880/Climate and Complexion
|CLIMATE AND COMPLEXION.|
THERE is a great diversity of opinion as to the reason of the differences of complexion to he observed among mankind. Roughly-speaking, the hue of the skin varies with the latitude, the fairer races having their homes at a distance from the equator; the darker, within or near the tropics. This fact would seem to point to the position of the sun with reference to those on whom he shines as the cause. But the question presents difficulties which this supposition does not aid us to solve.
At the same distance from the equator we find the fair Englishman, the yellow Mongol, and the copper-colored Indian. To the north of the white Russian and Finn live the swarthy Lapp and Samoyed. North of the Caucasus are dark-skinned Tartars, south of it fair-complexioned Circassians. The aborigines of America vary less in color than the natives of the Old World. None of them are as fair as the Swede, none as black as the negro of Congo, and those living in Brazil on the equator are not the darkest. There are blacker men in Australia and New Guinea than in Borneo and Sumatra, though these islands are on the equator and those are not. The Shillooks of the Upper Nile, who live about 10° north latitude, are blacker than the Monbuttoo who are six degrees farther south.
Many attempts have been made to explain these and similar facts. It has been asserted that mountaineers are fairer than lowlanders in the same latitude. This is generally the case, but there are some striking exceptions to the rule. The natives of the Mexican plateaus are as brown as those of the coast, and the Aymaras and Quichuas of the Peruvian Andes are darker than the Yuracaras of the forests to the east. The inhabitants of the Altai Mountains are yellow; those of the plains of European Russia, at the same distance from the equator, white. According to Foissac, the blackness of the negro is a consequence of his vegetable diet, by which his blood is overloaded with carbon. But this theory, likewise, breaks down when submitted to the test of a comparison with the facts. The nomads of the Asiatic deserts, who live mainly on milk and flesh, are certainly not fairer than the grain eating peasants whom they plunder; and the Buddhists of China and Japan, whose religion prohibits the use of animal food, do not differ in color from their neighbors of other creeds. The influence of humidity has attracted the attention of some writers. Sir R. and M. d'Orbigny hold that it tends to lighten, Dr. Livingstone and others that it tends to darken, the hue. I shall state below my reasons for agreeing with the former.
Mr. Charles Darwin, Professor Huxley, M. Quatrefages, and others, think it probable that racial distinctions owe their origin to the selective operation of the prevailing diseases of particular climates. Assuming, what is amply supported by facts, that individuals slightly diverging in various directions from the type are constantly being produced, it is obvious that if a dark or a light complexion be correlated with power to resist a particular disease, or group of diseases, a white race may, by natural selection, be gradually developed from a colored one, or vice versa. M. Quatrefages has suggested that the malarial fevers of Africa have wrought this effect there, and that phthisis has been the agent in *the north of Europe. It certainly is the case that the tropical regions of Africa are very unhealthy for whites, and that the negro dies out north of the parallel of 40° in both hemispheres; but this does not show that both races might not be acclimatized by slow degrees without loss of color. In other words, no reason has been shown for thinking that it is to the complexion and not to some other racial peculiarity that the relative immunity from certain maladies is due. To connect the color with this immunity is the object of this paper.
I may say at the outset that I do not attach much importance to the direct influence of climatic conditions. It is, indeed, a matter of common observation that these produce considerable effects on the individual. Primer, for example, states-that he has noticed that "the European acclimated in Egypt acquires after some time a tawny skin, and in Abyssinia a bronzed skin; he becomes pallid on the coast of Arabia, cachectic white in Syria, clear brown in the deserts of Arabia, and ruddy in the Syrian mountains." But there is no proof that these cutaneous changes are inherited. If, however, it can be shown that a particular kind of skin is better than others for withstanding certain obvious weakening influences of a given climate, it stands to reason that those members of a race whose skins vary in the direction of this type will in each generation have the best chance of surviving and begetting children, and that, by the continued increment of successive variations in the same direction, the skin and the climate will ultimately be brought into accord.
The skin consists of two layers: the inner, dense and fibrous, furnished with blood-vessels and nerves, called the dermis, or true skin; the outer, horny, nerveless, and bloodless, called the epidermis, cuticle, or scarf-skin. The cells which compose the latter originate in the rete Malpighii, its lowest part, are gradually forced outward by new cells, and finally exfoliate. In some of these epidermic cells a pigment is found which varies in different races, but always contains a yellow element. The hue of the skin does not depend on this coloring matter alone, but is a compound effect, resulting from the white of the dermis, the red of the blood in the minute vessels near the surface, the color and quantity of the pigment, and the thickness of the cuticle. Where the cuticle is thick, the color of the pigment will predominate over the other elements on account of the greater depth of pigment-cells. "Where it is thin, and the coloring matter light, the tint of the skin will be much affected by any change in the supply of blood to the capillaries at the surface of the body. This is the reason why the whites alone can turn pale and blush.
Closely related to the pigment of the skin are the coloring matters of the eye and hair. Dark-skinned people usually have black eyes and hair; fair hair and blue eyes are seldom found except in conjunction with a fair skin; and the eyes and hair of albinoes, in whom the pigment of the skin is wanting, are likewise destitute of coloring matter. The pink hue of their eyes is due to minute blood-vessels, whose color is masked in ordinary organs by the pigment of the iris.
It is noteworthy that the coloring matters of the epidermis and iris serve a very important purpose: they protect the tender underlying parts from the injurious effects of too much heat and light. Albinoes everywhere find it necessary to protect their skins and eyes from the effects of the sun's rays. In warm countries they seldom go out except at night. There is this difference between them and other men, that long-continued exposure to the sun, which ordinarily develops a condition of the skin capable of resisting its rays, does not do so in their case. It may here be remarked that the deeper the shade of the pigment, the more rays will it reflect, and the more effective will it be as a protective agency. On the contrary, the lighter the shade, the more light and heat will it permit to enter the body.
As an excretory organ, it is the function of the skin to discharge water, carbonic acid, and urea the first in large, the others in small quantities. Perspiration, or the excreting of water, with some saline matter in solution, is effected in two ways: In the first place, sudoriparous glands, imbedded in the true skin, secrete sweat from the blood. This is conveyed to the air by minute ducts passing through the epidermis. It is obvious that, the blacker the pigment, the less light and heat will be transmitted to excite these glands into activity. In the second place, there is a continual transudation of sweat from the minute vessels of the surface of the body through the epidermis at every point. The thicker or the more oily the scarf-skin, the less will the amount of this transudation be. If it be both thick and oily, as in many dark races, the quantity transuded will be reduced to a minimum; if it be thin and not oily, as in the fairest members of the white race, transudation will be copious.
The amount of transuded sweat depends, however, not merely on the thinness of the cuticle, but also on the degree to which the air in contact with the body is saturated with moisture; for there is a limit to the quantity of vapor which the air can absorb. This limit varies with the temperature, warm air absorbing more than cold. Such being the nature of the skin, I now proceed to inquire what kind of it will best suit particular regions. For this purpose climates may be classified as—
I. When the skin is exposed to great cold, perspiration by transudation is accelerated. The frosty air, raised many degrees in temperature by contact with the body, becomes very dry, and greedily drinks in its moisture. At the same time the body loses, not only the heat which the air carries off, but also that which is rendered latent by the evaporation of the sweat. As a protection against the injury which a too rapid loss of perspiration and heat may inflict in an arctic climate, a thick integument is desirable. On account of the obliquity of the sun's rays a dark pigment will be a disadvantage, because it will prevent the passage of light and heat. Some pigment will, however, be needed, as not even in northern regions can albinoes expose themselves to sunlight with comfort. The coloring matter, then, will be light; but, owing to the thickness of the cuticle, the general effect will be yellow.
II. By a humid temperate climate I mean one occurring in a temperate zone, in which the air constantly contains a large amount of moisture. Humidity does not to any considerable extent depend on the amount of the annual rainfall. The annual rainfall of London is twenty and one half inches, that of Toronto thirty inches; yet the air of the former place is incomparably more humid. Countries in which this climate is found are distinguished from others in the same latitude by the limited range of the thermometer. This is due partly to the fact that water can not be so rapidly heated as air, and partly to the check which the presence of haze, mist, or cloud in the atmosphere puts upon radiation. A humid temperate climate is also warmer than others in the same latitude, for it owes its existence in every case to breezes from warm seas. Breezes from cold seas can not produce a true humid temperate climate, because when they strike the land in summer they will be raised in temperature and rendered dry.
In humid temperate climates, since the rays of the sun, falling obliquely through a moisture-laden atmosphere, lose much of their light and heat, a dark pigment is a disadvantage. The vapor-clogged air tends to prevent perspiration, therefore a thin epidermis is desirable. The combination of a thin epidermis with a light pigment will give a fair complexion.
III. By a dry temperate climate I mean one occurring in a temperate zone in which the atmosphere is usually dry. Countries in which this climate prevails are distinguished from others in the same latitude by the great range of the thermometer. Their summers are hot and their winters cold. As a protection against the greater heat and brightness of the sun, a darker pigment than that which serves the purpose in humid temperate regions is necessary. To prevent the too rapid withdrawal of the fluid contents of the capillaries by the dry air, a thick cuticle is required. The combination of a thick cuticle with the pigment suitable to the intensity of the sun's rays will produce various shades of yellow and brown.
IV. By a humid tropical climate I mean one occurring in or near the torrid zone, in which there is no dry season. In such a climate vegetation will be luxuriant all the year round, and man will live in the shade of dense forests, in a steaming and enervating atmosphere, whose temperature will be high, but will vary little. Though the rays of the sun will descend vertically upon him, yet their power will be diminished by the vapor contained in the air, and he will not need so dark a pigment to protect him as the inhabitants of other tropical regions. Add to this, that a thin epidermis will promote perspiration which the moisture-laden atmosphere tends to check, and we come to the conclusion that the natives of such countries will be distinguished by comparatively fair complexions.
V. On the contrary, in a rainless tropical climate, or in one with a well-marked dry season, the rays of a vertical sun will continually, or for considerable periods, descend in all their power, and the blackest and densest pigment and the thickest scarf-skin will be needed. Between the tropics the nights are always long, and, in consequence, when in the dry season there is little moisture in the air to check radiation, the thermometer, as many African travelers have remarked, falls very low before sunrise. To withstand the loss of heat at such times a thick outer skin will be an advantage. Accordingly, in these climates, we find the blackest men and very thick skins.
This theory of the relations between the climate and the skin is, I believe, in accord with the facts. The polar tribes are known to be yellow. Among them, more frequently than elsewhere, according to Quatrefages, occur cases of dry, rough skins. This I take to be a result of the thickness of the cuticle, just as, on the older parts of a tree, the roughness of the bark is a consequence of its thickness.
It is well known that the climate of Europe, where white men most abound, is more influenced by the sea than that of any other continent. With the inconsiderable exception of the Caspian and Arctic regions, where yellow men occur, it may all be said to be kept moist by breezes from warm tracts of water. The fairest members of the human family are found in the humid lands about the North and Baltic Seas, where the influence of the Gulf Stream is most felt, and where a temperate climate extends farther from the equator than elsewhere on the face of the globe. When we proceed eastward from the Baltic, the complexions gradually darken as the increasing range of the thermometer indicates increasing dryness. Moscow, Kazan, and Tomsk are all near the fifty-sixth parallel of north latitude. The difference between the temperatures of the warmest and coldest months at these places is respectively 53°, 61°, and 69° Fahr. At Moscow, the population consists of fair- and dark-haired whites. About Kazan, though there are still fair and dark whites, there are also yellow men. At Tomsk the entire native population belong to the yellow race.
That the climate of the whole of Asia, from the Hindoo-Koosh and Himalaya Mountains northward, may be considered dry, is shown by the extensive deserts and the great range of temperature in the countries where sufficient rain falls to render agriculture possible. For instance, in China and Japan the range of the thermometer is somewhat greater than in corresponding latitudes in the eastern United States. The entire population of this vast area is yellow, with insignificant exceptions on its western border.
The greater part of North America corresponds in climate with central and eastern Asia. But the meteorological phenomena of the coast of British Columbia and Alaska are similar to those of the northwest of Europe. Warm winds from the Pacific keep the temperature high and the air moist; but, owing to the configuration of the coast and the direction of the mountain-ranges, their influence does not extend far inland. The immense difference between the climatic conditions of the eastern and western coasts of America may be illustrated by comparing the temperatures of Sitka (57° 3' N. L.) and Quebec (46° 49' N. L.). Though the latter is more than ten degrees farther south, its mean annual temperature is two degrees less, and, while the difference between the means of the warmest and coldest months is fifty-seven degrees at Quebec, it is only twenty-five at Sitka.
It is a fact which strikingly corroborates the theory advanced in this paper, that it is precisely in the northwestern part of this continent that the fairest natives are found. The testimonies of the early explorers, which have been collected and arranged by Mr. Bancroft, of San Francisco, in his valuable work on the Indians of the Pacific coast, leave no doubt that, before there was any intermixture of European blood in this region, the complexion of the inhabitants was not very different from that of southern Europeans, that their skins transmitted a blush, and that fair and brown hair, ruddy cheeks, and light eyes were not uncommon among them.
Perhaps the best example of a perpetually humid tropical climate is afforded by the valley of the Amazons. In consequence, nearly the whole of the vast region drained by this stream is, like some parts of India and some of the East Indian islands, covered with a dense unbroken forest. Though heated by an equatorial sun, its natives are, not only not black, but, as has already been remarked, lighter-complexioned than those of the Peruvian Cordilleras.
Examples of perpetually dry tropical climates are furnished by the Nubian Desert and the southern part of the Sahara. These countries, together with southern Arabia, enjoy the hottest mean summer temperature known. The inhabitants, whether belonging to the Semitic, the Hamitic, or the negro race, are alike black. The Nubian Arabs are said to be as black as the blackest negroes.
The part of Africa south of the Great Desert will exemplify the case of a tropical climate with a dry season. This immense region consists essentially of a strip of low coast-land, and an immense level central depressed surface, with a more or less elevated rim inclosing it. The inhabitants of the coast and the central depression are very black, those of the rim lighter in color. Dr. Livingstone attributes this difference to the greater humidity of the lower regions. But it is obvious, from theoretical considerations, that the rim must be more humid than any other part of the continent. During the dry season the sea-breezes, when they strike the coast, will be raised in temperature, and consequently deposit no moisture, until cooled by being forced upward when they come against some elevated land. The meteorological observations made in Africa support this view. Along the coast there is everywhere one pronounced dry season, and in some places there are two. In Sierra Leone (8° N. L.), it lasts from November to May; at the mouth of the Gaboon (0°), from May to September. In Zanzibar (6° S. L.) there are eight rainless months; in Natal (25°-30° S. L.) seven. The central depressed regions exhibit similar phenomena. At Gondokoro (5° N. L.) there are five, at Ujiji (5° S. L.) there are eight rainless months. On the contrary, in the Usagara Mountains (6° S. L.), which are west of Zanzibar, and in the elevated equatorial region about the Victoria Nyanza, rain falls every month of the year.
It was long ago remarked that the negro perspires less than the white. Pruner Bey has established by actual measurement that both his dermis and epidermis are thicker. I believe that these facts supply the explanation of the extreme unhealthiness of the African climate for the white man. His thin outer skin permits his system to be weakened by an undue loss of its fluids in the daytime and of its heat at night, and in this condition he falls an easy prey to some disease.
There are black men in Africa, India, and Australia, because these countries all have climates with long pronounced dry seasons. Owing to the peculiar formation of the continent of America, its tropical regions are more humid, and consequently no very dark natives are found there. Of the great Papuan race, which inhabits New Guinea and many smaller islands in that part of the Pacific, some branches are black and some brown; but I have not been able to procure meteorological data bearing on their case.
The climate and complexions of the rainless coast of Peru correspond very closely to those of the rainless valley of Egypt, the Peruvians being perhaps a shade darker. The dry climate of the tropical part of the Andes has even affected the color of the Spanish Creoles; while in Cartagena and Guayaquil, towns with a humid climate on the seacoast of South America, their complexion is as light as that of native Spaniards, and fair hair still occurs, in Santa Fé, which is in the mountain country, only dark complexions with dark hair are found. Tschudi, indeed, asserts that the colder the climate (i. e., the greater the elevation), the darker the color in Peru.
Some of the evidence tending to show the connection of humidity and fairness in Africa is quite striking. In the mountainous region of Gambaragara, near the Albert Nyanza there lives, according to Stanley, a race whose fairness so struck him that he supposes that it must have come from the north. According to Lefebvre, the skin of the Abyssinians becomes lighter during the rainy season. The Bongo, Niam-Niam, and Monbuttoo tribes, whose fairness amazed Schweinfurth, inhabit a wooded and presumably a humid country, while the black Shillooks, with whom he contrasts them, dwell in a country adapted to pastoral purposes, and therefore probably dry. In the rainy regions of the Atlas Mountains there are said to be tribes among whom many individuals with blue eyes, fair skin, and red beard occur.
Similar phenomena recur in Asia. The blonde races of the Caucasus are found on its moist southern slope. The races on the dry northern declivity have a Tartar complexion. The moistest part of India is the jungle-covered southern slope of the Himalaya Mountains, and in this quarter, accordingly, we hear of white races. The Rohillas, an Aryan people, living northeast of Delhi, and the Lepchas, a Mongolian tribe, near Darjeeling, may be mentioned as examples. In the north of China proper there is a low-lying, swampy, and presumably somewhat moist peninsula called Shantung. There is some evidence tending to show that the natives of this peninsula are fairer than the rest of the Chinese.
If this theory be correct, it is the destiny of the white race in North America to approximate in color to the aborigines. Two causes at present, to a considerable extent, counteract the effects of climate. The first is the constant influx of immigrants from the Old World; the second, the fact that, until the great West is filled up, the struggle for existence can not become very severe, and the degree of cutaneous adaptation to climate can not assume great importance. But there are, nevertheless, indications that climatic influences are producing their natural effect. The unmixed descendants of the original settlers everywhere appear to have dark hair and a more or less sallow complexion. The writer can testify from personal observation that this is generally the case with the descendants of the united empire loyalists who settled after the Revolution in what is now the Province of Ontario. He can also testify to the darkness of the French Canadians, who derive their origin principally from Normandy, and therefore may be assumed to have at first included a large number of fair-complexioned individuals. It is remarkable that among this race a great many persons are to be seen whose features are more or less Indian in type. This, however, may (as Dr. Wilson, of University College, Toronto, supposes) be the result of an admixture of native blood.
However similar, physically, our descendants may, under the influence of climate, become to the Indians, it by no means follows that they will resemble them mentally or morally. The same struggle for existence that will eliminate the individuals ill adapted to the physical climate will also eliminate those ill adapted to the intellectual and spiritual climate, so that I am inclined to predict that the result will show, what history has indeed already established, that capacity for progress is not indissolubly connected with any particular hue.
It is obvious that on this hypothesis agreement in color does not prove, and disagreement does not disprove, community of origin. Guided by linguistic affinities, ethnologists have already in many cases disregarded color in their classifications. In the Indo-European family they include both the fair Teutons and the dark Hindoos. The white Finns and Magyars are classed with the yellow Ural-Altaic races. Black Arabs and white Jews go together in the Semitic group. But the principle has not been applied throughout. The Basques and the Caucasians, between whose languages and those of the Aryan family no relationship has ever been established, are generally considered to be nearer in blood to us than those members of the Ural-Altaic group who exemplify in the fullest degree the Indo-European type of physique. Hitherto the ethnological results of investigations into the physical characteristics of different races have been mainly negative; the principal valuable positive conclusions have been derived from linguistic researches. In the dispute as to the relative merits of the zoölogical and philological methods in ethnology, I accordingly side with the advocates of the latter; and, in regard to the special subject of this paper, I say with Quatrefages, in the words of Virgil, "Ne crede colori."
- This paper embodies the substance of a communication made to the Canadian Institute, Toronto, at a recent meeting.
- Waitz, "Anthropology."
- Grisebach, "Vegetation der Erde."
- See a paper by J. Lamprey, in the "Transactions of the Ethnological Society" for 1867.