Instead of continuing the study of social evolution in general it will be best now, before we take up some of the problems of modern society, to study the evolution of some important social institution, because in so doing we can see more clearly the working of the biological and psychological forces which have brought about the evolution of human institutions. An institution, as has already been said, is a sanctioned grouping or relation in society. Now, there can be scarcely any doubt that the two most important institutions of human society are the family and property. In Western civilization these take the form of the monogamic family and of private property. It is upon these two institutions that our civilization rests. The state is a third very important institution in society, but it exists largely for the sake of protecting the family and property. Of the two institutions, the family and property, the family is without doubt prior in time and more fundamental,--more important in human association. We shall, therefore, study very briefly the origin and development of the family as a human institution in order to illustrate some of the principles of social evolution in general. But before we can take up the question of the origin of the family it will be well for us to see just what the function of this institution is in the human society of the present, in order to justify the assertion just made that it is the most important and fundamental institution of humanity. The Family the Primary Social Institution.--Let us note first of all that in society, as it exists at present, the family is the simplest group capable of maintaining itself. It is, therefore, we may say, the primary social structure. Because it contains both sexes and all ages it is capable of reproducing itself, and so of reproducing society. For the same reason it contains practically all social relations in miniature. It has therefore often been called, and rightly, "the social microcosm". The relations of superiority, subordination, and equality, which enter so largely into the structure of all social institutions, are especially clearly illustrated in the family in the relations of parents to children, of children to parents, of parents to each other, and of children to one another. Comte, for this reason, claimed that the family was the unit of social organization, not the individual. However this may be, it is evident that families do enter, as units, very largely into our social and industrial life. While the tendency may be to make the individual the unit of modern society, it is nevertheless true that the family remains the simplest social structure in society, and from it, in some sense, all other social relations whatsoever are evolved.