402 THE AMERICAN JOURNAL OF SOCIOLOGY
preventing close inbreeding.^ These differences may be perhaps set down to a difference in instincts between man and the higher animals. On the other hand, there are many differences which cannot be so explained, such as the fact that the indorsement of society is almost invariably sought among human beings before the establishment of a new family, usually through the forms of a religious marriage ceremony; that there exists a feeling of modesty regarding matters of sex ; and that chastity is enforced, on married women at least, among all peoples. While these peculiar traits of human family life may perhaps in part be traced to peculiar human instincts, yet the element of self-con- sciousness in each of them is so large and so manifest that they may be safely ascribed largely to man's intellectual nature. Thus the human family life illustrates both the instinctive origin of human association and its modification through intellectual ele- ments which have caused it to vary widely from the primitive animal type.
Here must be noticed the influence of the prolongation of human infancy upon human social life. This purely biological fact, whose importance John Fiske was the first to call attention to, has had a profound influence on both the instinctive and intel- lectual elements in human association, and especially on human family life. We have already noted how the prolongation of the period of immaturity of offspring affects social evolution in general, cementing the union between the parents and giving opportunity for the development of the sympathetic instincts and emotions within the family group. It is no doubt largely due to prolonged human infancy, therefore, that we have regularly in human society a permanent union between the parents lasting throughout life; permanent sympathetic relations between all members of a family group, giving rise to the sentiment of blood kinship; and a high development of sympathetic feeling and altruism in human society generally. It is, however, often over-
'In spite of the recent criticism of Westermarck's theory that there is a special instinct in man preventing incest it would seem that his theory must be accepted in a modified form ; for the criticism comes to this, that there is an instinctive tendency in human beings to be attracted sexually only toward relatively strange and unfamiliar persons.
