Thrupples

All 156 homosexual couples in one sample who had been together for over five years, described their relationships as being open, indicating that having an open relationship may be related to couple longevity.

Bisexual women appear numerous in polyamorous communities; the standing joke being that they can “have their Jake and Edith too”. According to Zimmerman, research confirms homosexual couples are much more likely to allow extra-dyadic sex. Two thirds of male couples of all durations are in sexually open relationships.

Swinging is non-monogamy in a social context, also referred to as “the lifestyle”, ‘Polyamory’ allows for partners to have more than one relationship that is sexual, loving, and emotional. ‘Polyfidelity’ refers to three or more people who have made a commitment to be in a primary relationship together. A monogamous/non-monogamous partnership is one in which one person is monogamous and the other is not.

optimal evolutionary strategy is to appear monogamous while being polygamous covertly

Monogamy is also the exception to relationships throughout the animal kingdom. Zimmerman cites work contending that of 4,000 mammal species, only about 3%, have been found to be monogamous, plus of the world’s roughly 400 species of primates, monogamy has been reported for only nine.