Mainly because of its universality the incest taboo has been a field of investigation open to a number of disciplines. The author reviews the most important theories concerning the bases of this taboo, arranged according to the point of view, finalist or determinist. He then considers the anew in the light of recent acquisitions stemming from ethology and family theory. It has been demonstrated that an instinctive barrier against incest exists in the family life of wild animals, bringing into play defence mechanisms analogous to those that obtain in the human family. Developing the subject, the author shows on the one hand how this discovery calls in question certain postulates hitherto regarded as definitive, and on the other hand how it opens the way to a more synthetic view of the problem.