Innumerable details of primitive legislation separate the son-in-law from the mother-in-law, the father-in-law from his son's bride.
The Basogas of the Upper Nile loathe incest to such a degree that they punish it even in animals whenever it can be observed among them.
=Incest in Ancient Times.= The horror of incest, however, is a relatively recent development in human psychology and ethics. The ancient dynasties of Egypt and Peru practiced incest. Incest was indulged in by all the archaic gods. The authors of the book of Genesis must have accepted the idea of incest as the sole means of explaining Adam's and Eve's descendants.
The horror of incest which we all feel or pretend to feel, is indeed an acquired feeling. Since every race has adopted stern legal measures to prevent incest, it can only be because a desire for incest is one of the cravings which mankind is constantly struggling against.
As Frazer says: "There is no law commanding men to eat and drink or forbidding them to put their hands in the fire. Men eat and drink and keep their hands out of the fire instinctively."
If men and women avoided incest instinctively no legislation would be needed compelling them to avoid it.
Indeed the confessions received by psychoanalysts reveal that the first sexual desires of the young are directed toward children of the opposite sex within the family circle. The many slight or serious indiscretions of an incestuous nature in which neurotic brothers and sisters indulge in infancy and childhood are generally "forgotten," that is, repressed, in later years, but analytic probing brings a great amount of such repressed material to the surface.
Since neither animals nor human beings experience any natural fear of incest, why is it that all races are officially so afraid of it?
=Inbreeding.= It cannot be due to the fear of race deterioration consequent upon inbreeding. Inbreeding is not necessarily a harmful process of reproduction as East and Jones have shown in their book on "Inbreeding and Outbreeding." It seems to have, at times, for instance in Athens during the classic age, led to the production of many very superior individuals.
Furthermore the primitive savages who punish incest even among domestic animals have no conception of such eugenic theories. Some of them, incredible as it may sound, do not even realise the relation of cause to effect which exists between intercourse and pregnancy.