Claire Hutchison

Opinions on current affairs & news in science


Homosexuality commonplace across the Animal Kingdom

It has long been acknowledged that animals engage in homosexual intercourse. However, up until recently, it was seen as out of the ordinary. Now, it has been agreed that as many as 1,500 species across the animal kingdom have sex with members of the same sex.

One such example is the Japanese macaque. A study discovered that during mating season, males compete with not only other males but females also. Furthermore, female partners are seen to treat each other as companions by grooming each other and fending off other potential suitors. Despite this, each of the females also engaged in intercourse with males. Similar behaviour is shown by Bonobos and bottlenose dolphins. It could be said that these species are bisexual.

Some bird species even mate for life with members of the same sex. Examples include the Laysan albatross. On the Hawaiian island of Oahu, as many as 31 per cent of couplings are between females.  These birds commonly make lifetime pairings and rear young that they produce with other males who already have a partner. Thus, these animals also engage in heterosexual sex. Arguably such behaviour is only exhibited as an evolutionary adaptation to be able to rear infants whilst the male population is in shortage.

A slightly different case is found with fruit flies and flour beetles, both of whom use other males to ultimately copulate with females. The male fruit flies often attempt to have sexual relations with other males. Unlike macaques however, these animals only exclusively mate with females when they can distinguish between the two sexes using their sense of smell, suggesting that their homosexual behaviour is accidental. They are using a trial and error method to be able to mate efficiently. Similarly, flour beetles often deposit sperm onto other males in order to pass their own genes on when said male mates with another female.

The only species, other than humans, which exhibits solely homosexual behaviour is the domestic sheep. Up to eight per cent of males preferentially copulate with other males, even when females are in surplus. Scientists have even found a link between the brain structure of men and sheep in which homosexuals of each species have a smaller hypothalamus than their heterosexual counterpart.

The idea of homosexual behaviour in animals can be a confusing concept as it is a preconception in science that all animals compete to mate in order to pass on their genes. This idea stems from Darwin’s Theory of Evolution by natural selection. However, scientists have hypothesised that in some cases this behaviour can be beneficial. In every case, except domestic sheep, the animal also mates with the opposite sex. Therefore, homosexual copulation provides pleasure and helps animals bond with one another. This allows them to function better as a group and improves survival. In the case of fruit flies and flour beetles, this sexual behaviour inevitably assists the males in passing on their genetic material. Furthermore, for albatross, same sex coupling acts as a solution to an unbalanced male to female ratio whilst still producing young. Homosexuality in domestic sheep does not benefit the males engaging in said behaviour themselves. However, it benefits their relatives. The female siblings of homosexual sheep tend to be more fertile and eager to mate than the average female. Therefore, the genes of the homosexual sheep are still more likely to be passed on.

In a surprising twist, homosexual behaviour in the animal kingdom does not in fact disprove Darwin’s theory, but rather reinforces it. In addition to this, though domestic sheep may be the only other species that exhibits definitive homosexuality, sex and pairing with both sexes is commonplace in the Animal Kingdom.


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