William Graham Sumner,
Folkways
“ Incest taboo strongest in the strongest groups. We shall see, in the cases to be presented, that incest has a wider definition and a stricter compulsion in great tribes, and in prosperity or wealth, than in small groups and poverty. The definiteness of this taboo, and the strictness with which it is enforced, seem to be correlative with the energy of the tribal discipline in general and the vigor of the collective life of the group. Wives can be got abroad, either by capture or contract, only by those who command respect for their power or who use power. ”
