INTRODUCTION TO SOCIOLOGY 561
average. The exogamy that we meet as a social institution among the least advanced societies, and which is at first practiced by rape and violence, is therefore a matrimonial form eminently advantageous to the development of societies in their ensemble. This is a mode of assimilation from without to within, of intro- susception parallel to the military organization almost universal in primitive societies. It is a case of organic and static correla- tion advantageous in its results, although accompanied by a great loss of force in its violent processes.
However, these exogamic societies are already in part differ- entiated and organized. They are far from representing to us the most homogeneous and most primitive stages of the human species. In the early geologic ages, on the contrary, the uniform distribution of organisms coincided with the persistence of the factors less favorable to the extension of humanity. In these conditions the growth and extension of the latter were doubtless very slow and very difficult, especially if we take account of the general lowering of the temperature in the polar regions.
It was by insensible selections and adaptations that the human species adjusts itself to the several climates. Man, taken by him- self, is cosmopolitan. The species, the varieties, the individuals, and also their groupings, on the contrary, are held within much more narrow limits. They are the result of adaptations heredi- tarily determined, and therefore in great part are refractions from the new variations. They are not the point of departure, but the product of evolution.
The negroes die faster the farther they are removed from the tropics, and the hyperboreans die faster the nearer they approach the tropics, for the reason that, through the successive variations, they have been more and more differentiated and adapted to special habitats, and that, through continued selection and heredity, their distinctive characteristics have been more and more accentuated and consolidated.
Therefore the conquest of the globe by the human species has been accomplished by the spontaneous and artificial creation of special forms, types, races, and sub-races ; or, in other words, of a progressive equilibration more and more special and complex