Page:The Origin of the Family, Private Property and the State.djvu/64

58 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, pbysically 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