We shall attempt to show that at least one form of taboo, the Institutionalized Sex Taboo, is co-extensive with human social experience, and exists to-day at the base of family life, the socialized form of sex relationship. The family as a social institution has been scarcely touched until a very recent historical period by the rationalizing process that has affected religious and political institutions. Economic changes resultant upon the introduction of an industrial era which showed the importance of women in diverse social relations were causes of this new effort at adaptation to changing conditions. It became apparent that taboos in the form of customs, ceremonials, beliefs, and conventions, all electrically charged with emotional content, have guarded the life of woman from change, and with her the functions peculiar to family life. There has doubtless been present in some of these taboos "a good hard common-sense element." But there are also irrational elements whose persistence has resulted in hardship, blind cruelty, and over-standardization. In order to comprehend the attitude of early man toward sex and womanhood, and to understand the system of taboo control which grew out of this attitude, it is only reasonable to suppose that the prehistoric races, like the uncivilized peoples of the present time, were inclined to explain all phenomena as the result of the action of spiritistic forces partaking of both a magical and religious nature. This supernatural principle which the primitive mind conceived as an all-pervading, universal essence, is most widely known as _mana_, although it has been discussed under other names.[A] Certain persons, animals and objects[B] are often held to be imbued to an unusual degree with this _mana_, and hence are to be regarded as holy and held in awe. Inasmuch as man may wish to use this power for his own purposes, a ceremonial cult would naturally grow up by which this would become possible. Otherwise, to come in contact with these objects directly or indirectly, besides profaning their sanctity would be exceedingly dangerous for the transgressor, because of this same power of transmission of a dread and little understood force. Therefore, all such persons, animals or objects are taboo and must be avoided. Under these circumstances it can be seen that taboos are unanalyzed, unrationalized "Don'ts," connected with the use and wont which have crystallized around the wish of man to manipulate the mysterious and often desirable features of his environment, notably those connected with possession, food, and sex. [Footnote A: The Australians call it Arunkulta, the Iroquis Indians Orenda and other North American tribes Wakonda, the Melanesians Mana.]