SOCIAL DIFFERENTIATION AND INTEGRATION 725
mother-group. As they moved out along special and extremely irregular lines, in the manner already described, there were soon produced many such terminal groups, and these were usually remote from each other, often separated by seas or mountain chains.
The period during which this process was going on, however long it may have been, may be called the period of social differ- entiation. In it languages were formed, but, owing to gradual isolation, each group acquired a language of its own. At least the variation that would* naturally take place in the language of any group would soon render it practically a different language from that of any of the remoter groups from which it had descended. A fortiori would the languages of all the terminal groups be different from one another. It would be the same with customs. The differences of environment would alone accomplish this, but customs naturally tend to vary, and unless there be intercommunication, they rapidly differentiate. The customs as well as the languages of all the different radiating lines would be utterly unlike except in certain fundamentals. When customs and ceremonials at length took the form of cults and religions, these, too, were different, and all the scattered groups ultimately presented the utmost heterogeneity in all their social characteristics. Between them the only points of agree- ment were biological. They still all belonged to the same genus and the same species, and were all equally men.
We have thus far pictured the scattered hordes as wholly isolated or only feebly joined to their ancestral groups along certain irregular lines by vanishing threads of memory and unor- ganized tradition. This would grow weaker and weaker as they receded from the primitive cradle, until everywhere on the remoter periphery all social connection would be lost. The different lines would be of very unequal length, and, as a matter of history, some of them reached out to the peopling of distant continents. All the social differences and certain physiological modifications due to differences of climate in the regions occu- pied, taken together, are what have finally produced the different races of men, and all the differences that exist among human
