Unlike some other sexual activities, vaginal intercourse has rarely been made taboo on religious grounds or by government authorities, as procreation is inherently essential to the continuation to the species or of any particular genetic line, which is considered to be a positive factor, and indeed, enables most societies to continue in the first place.
Many of the cultures that had prohibited sexual intercourse entirely no longer exist; an exception is the Shakers, a sect of Christianity that has four adherents at current. There are, however, many communities within cultures that prohibit their members to engage in any form of sex, especially members of religious orders and the priesthood in the Roman Catholic Church and priests in Buddhist monasteries.
Within some ideologies, coitus has been considered the only “acceptable” sexual activity. Relatively strict designations of “appropriate” and “inappropriate” sexual intercourse have been in human culture for hundreds of years. These legal or cultural restrictions may include:
- Sex among partners who are not married (this is sometimes referred to as fornication)
- Sex between a married person and someone to whom they are not married. (called adultery or extramarital sex)
- Commercial sex (called prostitution).
- Sex between partners of the same sex (called homosexuality).
- Sex between close relatives (called incest).
- Adults having sex with children (also called child sexual abuse, related to pedophilia).
- Humans having sex with non-human animals (called bestiality).
- Sex between members of different tribes, ethnic groups, or races, as in South Africa or the United States during periods of racial segregation.
- Sexual intercourse during a woman’s menstrual period, as in Islam and Judaism.
Often a community adapts its legal definitions during case laws for settling disputes. For example, in 2003 the New Hampshire Supreme Court ruled that same-sex relations do not constitute sexual intercourse, based on a 1961 definition from Webster’s Third New International Dictionary, in Blanchflower v. Blanchflower, and thereby an accused spouse in a divorce case was found not guilty of adultery based on this technicality.
Most countries have age of consent laws specifying the minimum legal age for engaging in sexual intercourse. Sexual intercourse with a person against their will, or without their informed legal consent, is referred to as rape, and is considered a serious crime in many cultures around the world, including those found in Europe, northern and eastern Asia, and the Americas. Sex, regardless of consent, with a person under the age of consent is often considered to be sexual assault or statutory rape. The age of consent varies from country to country and often by state or region; commonly, the age of consent is set anywhere between twelve and eighteen years of age, with sixteen years being the most common age the law sets. Sometimes, the age of consent is lowered for people near the same age wishing to participate in intercourse. For example, in Canada, the minimum age of consent for all couples is 14.
However, the age of consent can go below 14 on the condition that the couple still are not 2 years of age apart. Religions may also set differing ages for consent, with Islam setting the age at puberty, which can vary from around 10 to 14. There are exceptions in the case of anal sex or people in a position of trust/authority.
Another view of the “consent” determinate factor for rape can be applied to a relationship between adults where one party has lied to the other. Because their relationship contract is built on false grounds, the party lied to cannot truly consent, and has been raped if they have sex.