§ 76. As there has been an advance by degrees from unconscious parental altruism to conscious parental altruism of the highest kind, so has there been an advance by degrees from the altruism of the family to social altruism. A fact to be first noted is that only where altruistic relations in the domestic group have reached highly-developed forms, do there arise conditions making possible full development of altruistic relations in the political group. Tribes in which promiscuity prevails, or in which the marital relations are transitory, and tribes in which polyandry entails in another way indefinite relationships, are incapable of much organization. Nor do peoples who are habitually polygamous show themselves able to take on those high forms of social co-operation which demand due subordination of self to others. Only where monogamic marriage has become general and eventually universal--only where there have consequently been established the closest ties of blood--only where family altruism has been most fostered, has social altruism become conspicuous. It needs but to recall the compound forms of the Aryan family, as described by Sir Henry Maine and others, to see that family feeling, first extending itself to the gens and the tribe, and afterward to the society formed of related tribes, prepared the way for fellow feeling among citizens not of the same stock. Recognizing this natural transition, we are here chiefly concerned to observe that throughout the latter stages of the progress, as throughout the former, increase of egoistic satisfactions has depended on growth of regard for the satisfactions of others. On contemplating a line of successive parents and offspring, we see that each, enabled while young to live by the sacrifices predecessors make for it, itself makes, when adult, equivalent sacrifices for successors, and that, in default of this general balancing of benefits received by benefits given; the line dies out. Similarly, it is manifest that in a society each generation of members, indebted for such benefits as social organization yields them to preceding generations, who have by their sacrifices elaborated this organization, are called on to make for succeeding generations such kindred sacrifices as shall at least maintain this organization, if they do not improve it: the alternative being decay and eventual dissolution of the society, implying gradual decrease in the egoistic satisfactions of its members.