the relatives of their system of kinship, and this comprises several hundred kinds. By this increasing complication of marriage restrictions, group marriage became more and more impossible; it was displaced by the pairing family. At this stage one man lives with one woman, but in such a manner that polygamy, and occasional adultery, remain privileges of men, although the former occurs rarely for economic reasons. Women, however, are generally expected to be strictly faithful during the time of living together, and adultery on their part is cruelly punished. But the marriage-tie may be easily broken by either party, and the children belong to the mother alone, as formerly.
In this ever more extending restriction of marriage between consanguineous relations, natural selection also remains effective. As Morgan expresses it: "Marriages between gentes that were not consanguineous produced a more vigorous race, physically and mentally; two progressive tribes intermarried, and the new skulls and brains naturally expanded until they comprised the faculties of both." Thus tribes composed of gentes necessarily either gained the supremacy over the backward ones or, by their example, carried them along in their wake.
The development of the family, then, is founded on the continual contraction of the circle, originally comprising the whole tribe, within which marital intercourse between both sexes was general. By the continual, exclusion, first of near, then of ever remoter relatives, including finally even those who were simply related legally, all group marriage becomes practically impossible. At last only one couple, temporarily and loosely united, remains; that molecule, the dissolution of which absolutely puts an end to marriage. Even from this we may infer how little the sexual love of the individual in the modern sense of the word had to do with the origin of monogamy. The practice of all nations of that stage still more proves this. While in the previous form of the family the men were never embarrassed for women, but rather had more than enough of them, women now became scarce and were sought after.