Taboo refers to practices that are generally prohibited because of religious or social pressures. Some sexual behaviors have been taboo throughout history and remain so today. These include behaviors such as incest and rape, as well as many paraphilias such as pedophilia (sexual abuse of children by unrelated adults), necrophilia (sexual arousal from viewing or having sex with a corpse), and bestiality (sexual relations with an animal).

Other sexual behaviors that were once taboo no longer are, even though they may not be as approved as some other behaviors that have been accepted as "natural" or "normal".

Taboo Sexual Behaviors
Included in this category are masturbation, oral and anal sex, homosexuality, some forms of bondage, and sex with a menstruating woman. This change can in part be attributed to societies' gradual acceptance of what constitutes normal and harmless sexual experiences between consenting adults.

Incest
Incest is a behavior that is considered taboo and illegal in nearly all societies. Incest refers to any kind of sexual contact (oral, anal, or vaginal sex, fondling, or masturbation) between members of the same family. Definitions of what constitutes a family member vary, but ordinarily they include not only parents and siblings, but grandparents, uncles and aunts, nieces and nephews, step kin, and in most cases, first cousins.

The incest taboo is thought to protect families and society from the negative effects of inbreeding, once common among European royalty and in some other societies.

Masturbation
Masturbation has historically been a taboo, but is now viewed as normal by nearly all medical authorities and social scientists. Even the majority of people in our society now understand masturbation to be a common sexual behavior that is not harmful.

A number of studies in the last several years indicate that attitudes toward masturbation have relaxed considerably compared to earlier times.

Though the Bible has no clear-cut prohibitions against this sexual activity, both traditional Judaism and Christianity generally regard masturbation as sinful. The Catholic Church in the Vatican paper "Declaration on Sexual Ethics" (December 29, 1975) noted that "masturbation is an intrinsically and seriously disordered act." Thus, masturbation has been described as "self-abuse," "defilement of the flesh," and "self-pollution."