Historically, one of the ways in which individuals have avoided becoming pregnant is through anal instead of vaginal penetration by the penis. Because the anus is rich in nerve endings and is involved in the sexual response whether or not it is directly stimulated, some people enjoy this form of intercourse. One of the best-documented uses of anal intercourse is among the Manichaeans, a religious rival to early Christianity and about whom we know a lot from the writings of Saint Augustine. The Manichaeans held that its members should not engage in reproductive activity, and for those who could not be continent, anal intercourse seemed a way of having sex without the consequence of pregnancy. Augustine, who mentions the practice several times, seems to imply that this practice was followed only by heretical Manichaeans and reported that it was engaged in by both male and female partners, that is, homosexual and heterosexual couples.
Because the anus does not lubricate very well, some form of lubrication, such as K-Y Jelly or other forms of sterile, water-soluble solutions, has to be provided. Petroleum-based lubricants should not be used in the rectum, or for that matter in the vagina, because they tend to accumulate and are not as easily discharged as those that are water soluble. Oil-based lubricants also weaken barrier contraceptive devices, including the condom.
The anal sphincter responds to penetration with an initial contraction that may be uncomfortable. In a tense, inexperienced person, the contraction may last for a minute or longer, whereas those experienced in this form of intercourse appear to relax much more quickly, and the spasm lasts less than thirty seconds. Usually, when the spasm has run its course, the discomfort disappears. William Masters and Virginia Johnson in their studies of the human sexual response found that in eleven of fourteen episodes involving penetration of a female anus by a male, the female had an orgasm. Some researchers have found that 25 percent of American women have engaged in anal intercourse at least once, and ten percent do so regularly for pleasure. Most respondents, however, do not find it appealing.
Rectal intercourse carries risks and discomfort that can be overcome by proper care. Feces that could become smeared externally or block entry should be emptied from the rectum beforehand by an enema. The anal canal and rectum are easily damaged, so vigorous thrusting may tear the anal or rectal wall, causing hemorrhage or a serious local infection.
Heterosexual couples who engage in anal intercourse should be cautioned that vaginal intercourse ought not to be started immediately after anal sex. The penis should be thoroughly