594 THE AMERICAN JOURNAL OF SOCIOLOGY
of similar groups, and there can be no change or variation, and therefore no progress or structural advance. Throughout the protosocial, as throughout the protozoic, stage there is no struc- tural development, no evolution. The differentiation consists simply in the multiplication of practically identical clans. Just as organic evolution began with the metazoic stage, so social evolu- tion began with the metasocial stage. So, too, as the metazoic stage was brought about through the union of several or many unicellular organisms into a multicellular organism, so the meta- social stage was brought about by the union of two or more simple hordes or clans into a compound group of amalgamated hordes or clans. In the organic world the result was the forma- tion of tissues, the multiplication of organs, and the integration of the parts thus united into complete organisms. In the social world the result was the formation of what may be properly called social tissues, the multiplication of social organs, and the integration of all the elements thus combined into peoples, states, and nations. The study of social structure properly begins here ; but social structure would be wholly unintelligible without a clear idea of both the principle and the materials of social struc- ture. The principle is the interaction of antagonistic forces, and the materials are the primitive hordes and clans brought into existence by the process of social differentiation. We have now to descend from generalities and inquire into the specific character of social integration. A great area has become inhabited by innumerable human groups, but there is no organic connection between them. Each group lays claim to a certain area of terri- tory, but they begin to encroach upon one another. Two groups thus brought into proximity may be, and usually are, utterly unknown to each other. The mutual encroachment is certain to produce hostility. War is the result, and one of the two groups is almost certain to prove the superior warrior and to conquer the other. The first step in the whole process is the con- quest of one race by another. This is the beginning of the struggle of races of which we have all heard so much. Most persons regard this struggle as the greatest of all human mis- fortunes. But the sociologist studies the effects of race-struggle
