That there is truth in the view is shown by the fact that the degree to which the love of activity is developed seems to vary roughly with the severity of the climate even among the closely allied races of Europe. As we pass northward from the coast of the Mediterranean, we find the quality more and more strongly marked; and it is in accordance with this principle that the dominant power, the leadership in civilisation, has passed gradually northwards in the historic period. Civilisation first developed in the sub-tropical regions, in which the abundance of nature first gave men leisure to devote themselves to things of the mind, to contemplation and inquiry; while the northern races were still battling as savages against the inclemency of the climate, were still being ruthlessly weeded out by the rigorousness of the physical environment, and so were being adapted to it, that is to say, were being rendered capable of sustained and vigorous effort. But, as the means of subduing nature and of protecting himself against nature have been developed by man, the dominance has passed successively northwards to peoples whose innate energy and love of activity were more highly developed in proportion to the severity of the selection exerted upon many preceding generations. The severe climate has not been the only cause of this evolution of an energetic active type. No doubt military selection played its part also. The Northern races of Europe, more particularly the Nordic, the fair-haired long-headed race, underwent a prolonged and severe process of such military group selection, before branches of it settled in our island; and, among the qualities which must have tended to success and survival in this process, energy and capacity for prolonged and frequent effort, especially bodily effort, must have been one of the chief. Still, even such group selection was probably a secondary result of the direct climatic selection; for it must have been the love of activity and enterprise that led these peoples perpetually to wander, and so to come into conflicts with one another, conflicts in which the more energetic would in the main survive and the less energetic succumb. In part also it must have been determined in the third and the most indirect manner in which physical environment shapes racial qualities—namely, by determining occupations and modes of life, and through these the forms of social organisation, both of which then react upon the racial qualities.