Homosexuality, evolution and humans

Why doesn’t homosexuality become extinct?

Do homosexual animals have offspring? In some animal species it seems homosexuality runs in the family, and sometimes it actually pays off, in evolutionary terms. Among birds, homosexual pairs obtain eggs from “one night stands”, and raise the chicks. Homosexual penguins, swans, geese, ducks and seagulls are known to successfully raise families in this way.

tOccasionally two male flamingos raise families. They obtain eggs by one or both mating with a female. Except for that one occasion, they mate exclusively with each other. Two males can hold a much larger territory than a regular flamingo pair, thus more chicks can grow up. Photo: Eva M. Lauritzen, NHM, Oslo

Most animals – including humans - copulate far more than is necessary for reproduction. Most animals where homosexuality is observed are bisexual. Homosexual mating can pay off or be a drawback, depending on the circumstances, but most of the time it has little evolutionary effect.

Either you’re with us or against us

Many social animals have complex social systems where individuals seek out allies for help and protection. Sex is an important way of strengthening such alliances, also between animals of the same sex. In some animals the whole species is bisexual, and homosexual relationships are prerequisites for joining a pack, making strict heterosexuality a disadvantage.

Many of the species where homosexuality is registered are just such intelligent social animals with complex hierarchies, like wolves, lions, whales and primates.

bavianHamadryas baboons are typical of many animals with homosexual alliances. Large, intelligent and fierce, a male would face stiff competition without his allies, bound to each other through homosexuality. Photo: Yngve Vogt, Apollon, University of Oslo, Norway

Our closest relatives

Humans belong to the apes together with two species of chimpanzees, gorilla, orang-utan, siamang and gibbons. Homosexuality is known from all groups, but there are great variations between species regarding gender, age and frequency, and even from group to group within the species. Compared to the other apes, human homosexuality is neither extremely frequent, nor particularly rare, and in our species too, the practice varies from one culture to the next

Against nature?

The Church Council of Nablus in 1120 AD wrote the first law where homosexuality was labelled a “Crime against Nature”. In the Renaissance, such texts found their way into the laws of many countries, leading to widespread oppression of homosexuals on the basis that it is “unnatural”.

We may have opinions on a lot of things, but one thing is clear: Homosexuality is found throughout the Animal Kingdom. It is not against nature.

Publisert 25. feb. 2009 08:43 - Sist endret 24. feb. 2012 11:14