Spencer goes on to say that these primitive human characteristics constitute the internal factors, with which sociology starts, and that the business of this science is to explain the evolution of all those subsequent “_phenomena resulting from their combined actions_.” Of these phenomena the chief, he says, are the following—monogamy as evolved from polygamy, polyandry, {35} and promiscuity; the higher family affections as developed by the monogamous family; and governmental and social organisation as developed in two ways—by the conduct essential to war and the conduct essential to industry. His conclusions, so far as possible, shall be given in his own words. To begin with marriage: in the earlier stages of society nothing resembling it existed. The nearest approach to a family was the mother and such children as could be kept alive without the help of the father; and as the children grew up, this rudimentary group dissolved. But “_from families thus small and incoherent_” there naturally and inevitably arose, in accordance with the tendency to variation by which the human units are characterised, and which is the basis of all evolutionary selection, “_families of divergent types_”—families founded on unions of which some were more lasting than others, of which some were unions between one mother and many fathers, some between one father and many mothers, and some between one father and one mother. This last-named type of union, and the family life resulting from it, had many practical advantages, such as the production of closer bonds between the several members of the family, and consequently the practice between them of more efficient co-operation. Accordingly, no sooner did monogamous groups appear than they exhibited a tendency to survive in the social struggle for existence; and monogamy affords, with the affections that have grown up under its shelter, the type {36} of marriage and family that prevails amongst the most advanced races of to-day.