It cannot be doubted that this greater similarity is due partly to the greater uniformity of the conditions of life to which uncivilized peoples are subject. According to Villermé and Quetelet, an inequality of stature is observed not only between the inhabitants of towns on the one hand and those of the country on the other, but also, in the interior of towns, between individuals of different professions.[1582] There is, however, another factor, which is, I think, of still greater importance. The deviations from the national type, which occur sporadically, have been considered the result of disease, and can, as Professor Waitz observes, “but rarely become permanent, as the national type is always that which harmonizes with the soil and the climate, and the external relations in which the respective peoples live.”[1583] We must assume that a certain kind of constitution is best suited for certain conditions of life, and that every considerable deviation from this must perish in the struggle for existence in a state in which natural selection is constantly at work and physical qualities are of the first importance. We know from Isidore Geoffroy’s investigations that persons who deviate much, with regard to the length of body, from the common standard—they may be dwarfs or giants—are, as a rule, abnormal in other respects also, being deficient in intelligence as well as in the power of reproduction, and being especially liable to premature death.[1584] Sir W. Lawrence, too, remarks that the strength of men who have considerably exceeded the ordinary standard has by no means corresponded to their size, and that “there are very few instances of what we can deem healthy, well-made men, with all the proper attributes of the race, much below the general standard.”[1585] If, among civilized peoples, such deviations indicate some disturbance of the vital functions, and, as a consequence, are unfavourable to existence, this must be even more the case with savage tribes, all the members of which are subject to nearly the same conditions of life. Abnormal characteristics may sometimes flourish in a highly civilized society, but they are doomed to perish in communities among whom the struggle for existence is far more severe.