While the human individual was best fed and guarded by the family, and so required the prompt, correlative action of all the members of that family, naturally the family must have a head; and that form of government known as the patriarchal was produced. The natural family relation, as seen in parents and young of other species, or in ourselves in later forms, involves no such governmental development: that is a feature of the family as a social entity alone. One of the essentials of the patriarchal family life was polygamy, and not only polygamy, but open concubinage, and a woman slavery which was almost the same thing. The highest period of the family as a social institution was a very low period for marriage as a social institution,—a period, in fact, when marriage was but partially evolved from the early promiscuity of the primitive savage. The family seems indeed to be a gradually disappearing survival of the still looser unit of the horde, which again is more closely allied to the band or pack of gregarious carnivora than to an organic social relation. A loose, promiscuous group of animals is not a tribe; and the most primitive savage groups seem to have been no more than this. The tribe in its true form follows the family,—is a natural extension of it, and derives its essential ties from the same relationship. These social forms, too, are closely related to economic conditions. The horde was the hunting unit; the family, and later the tribe, the pastoral unit. Agriculture and its resultant, commerce and manufacture, gradually weaken these crude blood ties, and establish the social relationship which constitutes the State. Before the pastoral era the family held no important position, and since that era it has gradually declined. With social progress we find human relations resting less and less on a personal and sex basis, and more and more on general economic independence. As individuals have become more highly specialized, they have made possible a higher form of marriage.