Varieties of monogamy

Recent discoveries have led biologists to talk about the three varieties of monogamy: social monogamy, sexual monogamy, and genetic monogamy. The distinction between these three are important to the modern understanding of monogamy.

Social, sexual, and genetic monogamy
Social monogamy refers to two people who live together, have sex with one another, and cooperate in acquiring basic resources such as food, clothes, and money. Sexual monogamy refers to two people who remain sexually exclusive with one another and have no outside sex partners. Genetic monogamy refers to the fact that two partners only have offspring with one another.

Monogamous pairs of animals are not always sexually exclusive. Many animals that form pairs to mate and raise offspring regularly engage in sexual activities with partners other than their primary mate. This is called extra-pair copulation. Sometimes these extra-pair sexual activities lead to offspring. Genetic tests frequently show that some of the offspring raised by a monogamous pair come from the female mating with an extra-pair male partner. These discoveries have led biologists to adopt new ways of talking about monogamy: "Social monogamy refers to a male and female's social living arrangement (e.g., shared use of a territory, behaviour indicative of a social pair, and/or proximity between a male and female) without inferring any sexual interactions or reproductive patterns. In humans, social monogamy equals monogamous marriage. Sexual monogamy is defined as an exclusive sexual relationship between a female and a male based on observations of sexual interactions. Finally, the term genetic monogamy is used when DNA analyses can confirm that a female-male pair reproduce exclusively with each other. A combination of terms indicates examples where levels of relationships coincide, e.g., sociosexual and sociogenetic monogamy describe corresponding social and sexual, and social and genetic monogamous relationships, respectively." (Reichard, 2003, page 4) Whatever makes a pair of animals socially monogamous does not necessarily make them sexually or genetically monogamous. Social monogamy, sexual monogamy, and genetic monogamy can occur in different combinations.

When applying these terms to people, it's important to remember that social monogamy does not always involve marriage. Social monogamy simply refers to two people who live together, have sex with one another, and cooperate in acquiring basic resources such as food, clothes, and money. A married couple is almost always a socially monogamous couple. But couples who choose to cohabit without getting married can also be socially monogamous.

Serial monogamy
The term serial monogamy does not refer to a fourth type of monogamy. The three types of monogamy recognized by biologists (social monogamy, sexual monogamy, and genetic monogamy) describe the relationship between a particular pair of partners. The term serial monogamy describes the history of a single individual across multiple socially monogamous relationships. In animals, serial monogamy often means that an animal will have a different, but exclusive, breeding partner each mating season.