SOCIAL DIFFERENTIATION AND INTEGRATION 723 SOCIAL DIFFERENTIATION.
The fundamental character that distinguishes man from all other species of animals is his greater brain development and consequent increased powers of all kinds. The first mental faculty to tell in his history was memory. In all other animals blood-relationship is almost immediately forgotten. In man it is remembered, and this is the basis of the kinship group which is the natural foundation of society. The primary social cohe- sion is the consanguineal bond. The horde is at first only a family, and it never becomes anything more than a kinship group. The clan is only a larger kinship group rendered pos- sible by higher mental powers and longer memory. Hordes and primitive clans, like animal cells, are limited in size, but not in growth, and the consequence in the one, as in the other case, is a multiplication by division. New hordes and clans are produced, and as these must each occupy different territorial areas, a pro- cess of expansion takes place. If the conditions of existence were everywhere the same, this expansion might take the form of a true circle, pushing out in concentric bands from the original center. But no such uniformity of conditions can be conceived of. The least diversity would suffice to give some trifling impetus to one radius in preference to another, and the form of the figure would begin to be irregular. In the actual state of things at any point on the earth's surface that anyone may please to select, the natural inequalities in the environment would at once produce great irregularities. The multiplying hordes would push out in only a few favored directions, would follow the water currents, string along the shores of seas or lakes, seek the nut- bearing forests and the bays abounding in shellfish, yielding to all the elements that promised an easier and more certain sub- sistence.
Another equally important mental faculty distinguishing man is cunning and inventive power. By means of this he was able to break over the faunal boundaries that limit the distribution of other species, and to overflow into other regions to which he was not originally adapted. All other species are restricted to special districts and unable to quit them. Every attempt to do so proves
