The study of primitive history leaves now no room for doubt that, at the lowest grades of human development, the relation of the sexes is totally different from that of latter times, and that a state of things resulted therefrom, which, looked at with modern eyes, appears as monstrous, and as a sink of immorality. Nevertheless, as each social stage of human development has its own conditions of production, so likewise has each its own code of morals, which is but the _reflection of the social condition_. That is moral which is usage; and that, in turn, is usage which corresponds with the innermost being, i. e., the needs of a given period. Morgan reaches the conclusion that, at the lower period of savagery, there was sexual intercourse between the several grades or generations, every woman belonging to every man, and every man to every woman,--in other words, promiscuity. All men live in polygamy and all women in polyandry. There is a general community of women and of men, but also a community of children, Strabo reports (sixty-six years before our reckoning) that, among the Arabians, brothers cohabited with sisters and with their own mother. On any route other than that of incest, the increase of population is nowhere possible, if, as alleged in the Bible also, descent from one couple is granted. The Bible itself contradicts itself on this delicate point. It is stated there that Cain, after he had murdered his brother Abel, took a wife of another people. Whence came that other people? The theory of promiscuity in primitive times, that is to say, that the horde was endogamous, that sexual intercourse was indiscriminate, is furthermore supported by the Hindoo myth, according to which Brahma married his own daughter Saravasti. The same myth turns up again among the Egyptians and the northern Edda. The Egyptian god Ammon was the spouse of his own mother, and boasted of it. Odin, according to the Edda, was the mate of his own daughter Frigga.[2] Morgan proceeds from the principle that, from the state of promiscuity, soon a higher form of sexual intercourse took shape. He designates this the consanguine family. Here the groups, that stand in sexual relation, are separated by grades or generations, so that grandfathers and grandmothers, within an age group, are husbands and wives. Their children, likewise, constitute a group of common couples; likewise the children of these, so soon as they have reached the requisite age. Accordingly, in contrast with the sex relations of the rawest period, in which promiscuity of sexes exists without distinction of age, now one generation is excluded from sexual intercourse with another. Sexual intercourse, however, exists between brothers and sisters, male and female cousins of the first, second and third remove. All of these together are brothers and sisters, but towards one another, they are all husbands and wives. This family-form corresponds with the system of