Popular Science Monthly/Volume 5/July 1874/Climate and Social Development
LIFE in general is possible only between certain limits of temperature; and life of the higher kinds is possible only within a comparatively narrow range of temperature, maintained artificially if not naturally. Hence it results that social life, presupposing as it does not only human life, but that life vegetal and animal on which human life depends, is restricted by certain extremes of cold and heat.
Cold, though great, does not rigorously exclude warm-blooded creatures, if the locality supplies in adequate quantity the means of generating heat. The arctic Fauna contains various marine and terrestrial mammals, large and small; but the existence of these depends, directly or indirectly, on the existence of the inferior marine creatures, vertebrate and invertebrate, which would cease to live there did not the warm currents from the tropics check the formation of ice. Hence such human life as we find in arctic regions, dependent as it is mainly on that of these mammals, is also remotely dependent on the same source of heat.
Here the fact we have to note is that, where the temperature which man's vital functions require can be maintained with difficulty, social evolution is not possible. There can be neither a sufficient surplus power in each individual nor a sufficient number of individuals. Not only are the energies of the Esquimaux expended mainly in defending himself against loss of heat, and in laying up stores by which he may continue to do this during the arctic night, but his physiological processes are greatly modified to the same end. Without fuel, and, indeed, unable to burn within his snow-hut any thing more than an oil-lamp, lest the walls should melt, he has to keep up that bodily warmth which even his thick fur dress fails to retain, by devouring vast titles of blubber and oil; and his digestive system, heavily taxed in providing the wherewith to meet excessive loss by radiation, supplies less material for other vital purposes. This great physiological cost of individual life, indirectly checking the multiplication of individuals, arrests social evolution.
A kindred relation of cause and effect is shown us in the Southern Hemisphere by the still more miserable Fuegians. Living nearly unclothed in a region of continual storms of rain and snow, which their wretched dwellings of sticks and grass do not exclude, and having little food but fish and mollusks, these beings, described as scarcely human in appearance, have such difficulty in preserving the vital balance in face of the rapid escape of heat, that the surplus for individual development is narrowly restricted, and, by consequence, the surplus for producing and rearing new individuals. Hence the numbers remain too small for exhibiting any thing beyond incipient social existence.
Though, in some tropical regions, an opposite extreme of temperature so far impedes the vital actions as to impede social development, yet hindrance from this cause seems exceptional and relatively unimportant. Life in general, and mammalian life along with it, is great in quantity as well as individually high, in localities that are among the hottest. The inertness and silence during the noontide glare in such localities do, indeed, furnish evidence of enervation; but in cooler parts of the twenty-four hours there is a compensating energy. And if it is true that varieties of the human race, adapted to these localities, show us, in comparison with ourselves, some indolence, this does not seem greater than, or even equal to, the indolence of the primitive man in temperate climates.
Contemplated in the mass, the facts do not countenance the current idea that great heat hinders progress. Many societies have arisen in hot climates, and in hot climates have reached large and complex growths. All our earliest recorded civilizations belonged to regions which, if not tropical, almost equal the tropics in height of temperature. India and Southern China, as still existing, show us great social evolutions within the tropics. And, beyond this, the elaborate architectural remains of Java and of Cambodia yield proofs of other tropical civilizations in the East; while the extinct societies of Central America, Mexico, and Peru, need but be named to make it manifest that in the New World, also, there were in past times great advances in hot regions.
It is thus, too, if we compare societies of ruder types that have developed in warm climates, with allied societies belonging to colder climates. Tahiti, the Tonga Islands, and the Sandwich Islands, are within the tropics; and in them, when first discovered, there had been reached stages of evolution that were remarkable considering the absence of metals. So that, though excessive heat hinders the vital actions, not only of man as at present constituted, but of the mammalia generally, such heat hinders the evolution of bodily energy only during part of the day, and, by the abundance of materials for living which it fosters, aids social development in most ways more than it impedes it in some ways.
I do not ignore the fact that in recent times societies have evolved most, both in size and complexity, in temperate regions. I simply join with this the fact that the first considerable societies arose, and the primary stages of social development were reached, in hot climates. Joining these two facts, the entire truth would seem to be that the earlier phases of progress had to be passed through where the resistances offered by inorganic conditions were least; that, these phases having been passed through, and the arts of life having been advanced, it became possible for societies to develop in regions where the resistances were greater; and that further developments in the arts of life, and further discipline in cooperation going along with them, enabled societies inheriting the resulting advantages to take root and grow in regions which, by climatic and other conditions, offered relatively great resistances.
Taking the most general view of the facts, we must therefore say that, solar radiation being the source of those forces by which life, vegetal and animal, is carried on, and being, by implication, the source of the forces displayed in human life, and consequently in social life, it results that there can be no considerable social evolution on tracts of the earth's surface where solar radiation is very feeble. We see that, though, contrariwise, there is on some tracts a solar radiation in excess of the degree most favorable to vital actions, yet the consequent hindrance to social evolution is relatively small. Further, we conclude that an abundant supply of light and heat is requisite during those first stages of progress in which social vitality is small.
Passing over such traits of climate as variability and equability, whether diurnal, annual, or irregular, all of which have their effects on human activities, and therefore on social phenomena, I will name here one other climatic characteristic that appears to be an important factor. I refer to the quality of the air in respect of dryness or moisture.
Either extreme brings indirect impediments to civilization, which we may here note before observing the more important direct effects. That great dryness of the air, causing a parched surface and a scanty vegetation, negatives the multiplication needed for advanced social life, is a familiar fact. And it is a fact, though not a familiar one, that extreme humidity, especially when joined with great heat, may raise unexpected obstacles to progress; as, for example, in some parts of East Africa (Zungomero), where, according to Captain Burton, "the springs of powder-flasks exposed to the damp snap like toasted quills;... paper, becoming soft and soppy by the loss of glazing, acts as a blotter;... metals are ever rusty;... and gunpowder, if not kept from the air, refuses to ignite."
But it is the direct effects of different hygrometric states which must here be more especially set down—the effects on the vital processes, and therefore on the individual activities, and, through them, on the social activities. There is good reason, inductive and deductive, for believing that the bodily functions are facilitated by atmospheric conditions which make evaporation from the skin and lungs tolerably rapid. That weak persons, whose variations of health furnish good tests, are worse when the air, surcharged with water, is about to precipitate, and are better when the weather is fine, and that such persons are commonly enervated by residence in moist localities but invigorated by residence in dry ones, are facts generally recognized. And this relation of cause and effect, manifest in individuals, is one which we may suspect holds in races—other things being equal. In temperate regions, differences of constitutional activity due to differences of atmospheric humidity, are less traceable than in torrid regions, the reason being, that the inhabitants are subject to a tolerably rapid escape of water from their surfaces, since the air, though well charged with water, will take up more when its temperature, previously low, is raised by contact with the body. But it is otherwise in tropical regions where the body and the air bathing it differ much less in temperature, and where, indeed, the air is often higher in temperature than the body. Here the rate of evaporation depends almost wholly on the quantity of surrounding vapor. If the air is hot and moist, the escape of water through the skin and lungs is greatly hindered; while it is greatly facilitated if the air is hot and dry. Hence, in the torrid zone, we may expect constitutional differences between the otherwise-allied inhabitants of the low, steaming tracts and the tracts which are habitually parched with heat. Needful as are cutaneous and pulmonary evaporation for maintaining the movement of fluids through the tissues, and thus furthering molecular changes, it is to be inferred that, other circumstances being alike, there will be more bodily activity in the people of hot and dry localities than in the people of hot and humid localities.
The evidence, so far as we can disentangle it, justifies this inference. The earliest recorded civilization grew up in a hot and dry region—Egypt; and in hot and dry regions also arose the Babylonian, Assyrian, and Phœnician civilizations. But the facts when stated in terms of nations are far less striking than when stated in terms of races. On glancing over the rain-map of the world, there will be seen an almost continuous area marked "rainless district," extending across North Africa, Arabia, Persia, and on through Thibet into Mongolia; and from within, or from the borders of, this district have come all the conquering races of the Old World. We have the Tartar race, which, passing the southern mountain-boundary of this rainless district, peopled China and the regions between it and India—thrusting the aborigines of these areas into the hilly tracts; and which has sent successive waves of invaders not into these regions only, but, from time to time, into the West. We have the Aryan race, overspreading India and making its way westward through Europe. We have the Semitic race, becoming dominant through North Africa, and, spurred on by Mohammedan fanaticism, conquering parts of Europe. That is to say, besides the Egyptian race, which, seeming by its alliances to have originally been of low type, became powerful in the hot and dry valley of the Nile, we have three races, widely unlike in type, and speaking languages classed as fundamentally distinct, which, from different parts of the rainless district, have spread as invaders over regions relatively humid.
Original superiority of type was not the common trait of these races: the Tartar type is inferior, as well as the Egyptian. But the common trait, as proved by subjugation of other races, was energy. And when we see that this common trait, in races otherwise unlike, had for its concomitant their long-continued subjection to these special climatic conditions—when we find further, that from the region characterized by these conditions, the earlier waves of conquering emigrants, losing in moister countries their ancestral energy, were overrun by later waves of the same races, or of other races coming from this region, we get strong reason for inferring a relation between constitutional vigor and the presence of an air which, by its warmth and dryness, facilitates the vital actions.
A striking verification is at hand. On turning to the rain-map, it will be seen that, of the entire New World, the largest of the parts distinguished by the absence of shade as almost rainless, is that Central American and Mexican region in which indigenous civilizations developed; and that the only other rainless district is that which formed part of the ancient Peruvian territory—the part, moreover, in which the pre-Inca civilization has left its most conspicuous traces. Inductively, then, the evidence justifies in a remarkable manner the physiological deduction.
Nor are there wanting minor verifications. Comparisons among African races are suggestive of similar contrasts in constitution, similarly caused. Of the varieties of negroes Livingstone remarks ("Missionary Travels," p. 78): "Heat alone does not produce blackness of skin, but heat with moisture seems to insure the deepest hue;" and Schweinfurth, in his lately-issued "Heart of Africa," similarly remarks on the relative blackness of the Denka and other tribes living on the alluvial plains, and contrasts them with "the less swarthy and more robust races who inhabit the rocky hills of the interior" (vol. i., p. 148). There seem, generally recognizable, corresponding differences in energy and social advance. But I note this difference of color arising in the same race, between those subject to a moist heat and those subject to a dry heat, for the purpose of suggesting its probable connection with the fact that the lighter-skinned races are habitually the dominant races. We see it to have been so in Egypt. It was so with the races spreading south from central Asia. There is evidence that it was so in Central America and Peru. And if, heat being the same, darkness of skin accompanies humidity of the air, while relative lightness of skin accompanies dryness of the air, then, in this habitual predominance of the lighter-complexioned varieties of men, we find further evidence that constitutional activity, and in so far social development, is favored by a climate conducing to rapid evaporation.
I do not mean that the energy thus resulting determines, of itself, higher social development: this is neither implied deductively nor shown inductively. But greater constitutional activity, making easy the conquest of less active races and the usurpation of their richer and more varied habitats, also makes possible a utilization of such habitats that was not possible to the aborigines.
- From advance sheets of the "Principles of Sociology.—Part I. The Data of Sociology. Chapter III. Original External Factors."