If this be so, it is plain that climate, and the conditions of life which depend upon climate, soil, and the presence of vegetables and of other animals besides man, must have been the forces which moulded and developed those varieties. From a remote antiquity, everybody has connected the dark colour of all, or nearly all, the races inhabiting the torrid zone with the power of the sun; and the fairer skin of the races of the temperate and arctic zones with the comparative feebleness of his rays in those regions. This may be explained on Darwinian principles by supposing that the darker varieties were found more capable of supporting the fierce heat of the tropics. What explanation is to be given of the other characteristics of the negro and negroid races, of the usually frizzled hair, of the peculiar nose and jaw, and so forth, is a question for the naturalist rather than for the historian. Although climate and food may be the chief factors in differentiation, the nature of the process is, as indeed is the case with the species of animals generally, sometimes very obscure. Take an instance from three African races which, so far as we can tell, were formed under similar climatic conditions--the Bushmen, the Hottentots, and the Bantu, the race including those whom we call Kaffirs. Their physical aspect and colour are different. Their size and the structure of their bodies are different. Their mental aptitudes are different; and one of the oddest points of difference is this, that whereas the Bushmen are the least advanced, intellectually, morally, and politically, of the three races, as well as the physically weakest, they show a talent for drawing which is not possessed by the other two. [Illustration: THE HABITATIONS OF MAN IN ALL AGES OF THE WORLD’S HISTORY At first man built twig huts in trees, but becoming better matched with his animal foes he took to caves and underground habitations. Our illustration of the latter shows a section through the soil. Lake dwellings marked a distinct advance. Other varieties of primitive habitations are the leaf hut, the tents of skin, the mud hut, and the beehive hut of stone. Roman villas are still models of beauty. American “skyscrapers” are peculiar to our time; but all early forms of dwellings, while marking progress, have existed contemporaneously throughout history. ] [Sidenote: Is the Race Mystery Insoluble?]