Incest

Incest consists of sexual relations between closely-related blood relatives. While the boundaries of incest vary from one culture/jurisdiction to another (first cousins? third cousins? "kissing cousins"?), the core forms of incest are agreed on universally: sex between parent and child, or between siblings.

It is sometimes believed that incest is and has always been abhorred everywhere and illegal in any culture developed enough to have laws. This is far from the case. In ancient Egypt, for example, sibling marriage of and reproduction by rulers was normal and institutionalized.

Genetic risk of inbreeding

The genetic deterioration and substandard offspring caused, or facilitated, by incest are well known in animal husbandry. The same phenomenon in European royal families, who even if not closely related had a limited pool of (biologically) related mates to choose from, has also caused degeneration in offspring, as in the seventeenth-century Spanish Hapsburgs. This biological fact is used to stigmatize and criminalize incest, although incest, like other types of sexual intercourse, does not necessarily lead to offspring. When the child has not reached puberty there is no risk.

Adult incest

Incest between individuals who are both over the age of consent, and which does not lead to reproduction, has become increasingly tolerated in Western countries. It is the subject of several Web sites and has been appearing in pornography more and more frequently since 2010. Prosecutions are rare, and there is an identifiable "pro-incest" movement (although this label is used by those opposed to incest). Prosecutions are rare.

Incest with minors

Incest between minor siblings is generally ignored, especially if they are close in age. However incest between parent and child is often viewed with the same horror as are other types of sex between adult and child. Its extent is unknown and has not been studied; what is known about it comes from legal cases, in which one or more other adults learn of it and go to the authorities, who categorize it as serious child abuse and usually results in the parent's incarceration and the destruction of the family. Since it takes place within the family it is shielded from public view. It is assumed that parent-child incest (or sometimes more accurately child-parent incest, since there are many documented cases in which the child was the initiator) is and has always been far more common than the public realizes, but this is speculative.

There are arguments to be made for adult-child incest, as long as it is loving and not abusive. Parents are the child's natural teachers: they teach the child to talk, to walk, in some cases to read, and so on. A loving parent is arguably the best person to teach a child about sex, and to pleasure the child (as opposed to censored "sex education" classes, peer gossip, pornography, or simply letting the child figure out sex with a peer as best he or she can). Certainly the parent has the easiest access. Some parents openly have sex in front of their children, who, once they understand what is happening, are invited to joinvthem in bed. Dads are the best people to teach their sons about the joy of gay sex.