Such primitive groups cannot grow into larger units, because these would demand more roots sent down into the sustaining soil; but they multiply by fission, like the infusorial monads, and thereafter lead independent existences remote from each other.

This is the explanation of multiplication of dialects among savage tribes.
[Sidenote: Land bond in fisher tribes.] Fishing tribes have their chief occupation determined by their habitats, which are found along well stocked rivers, lakes, or coastal fishing grounds.

Conditions here encourage an early adoption of sedentary life, discourage wandering except for short periods, and facilitate the introduction of agriculture wherever conditions of climate and soil permit.

Hence these fisher folk develop relatively large and permanent social groups, as testified by the ancient lake-villages of Switzerland, based upon a concentrated food-supply resulting from a systematic and often varied exploitation of the local resources.

The cooeperation and submission to a leader necessary in pelagic fishing often gives the preliminary training for higher political organization.[92] All the primitive stocks of the Brazilian Indians, except the mountain Ges, are fishermen and agriculturists; hence their annual migrations are kept within narrow limits.