Animals are part of the natural world, right? Well, there are over 1,500 animals that show some form of homosexual behaviour.
Let’s go through some colourful examples. Over nine in 10 of giraffe sexual encounters are between males rather than females. Our close cousins – the Bonobo or pygmy chimpanzee – have a matriarchal society with women trading sexual favours with each other as a way to resolve conflict. Surprisingly, even many insects and spiders seem to practise homosexuality once in a while.
Take fruit flies (Drosophila melanogaster), the darling of many geneticists. Males do all the effort in courting, and usually just over one in 20 of these sexual encounters are homosexual. But give the flies some alcohol and they then stop differentiating between either sex and mate with both sexes just as frequently.
Scientists have also found a gene called fruitless; flies have a male and female version of this gene. The scientists inserted the male version in females who then started courting other females. When they inserted the female version into males they stopped courting altogether.
Nearly eight in 10 genes in humans that cause disease have a similar gene in flies.
Studies in mice have also shown that genes influence mate choice. The researchers knocked out a gene that made the neurotransmitter serotonin in the brain. Serotonin is very important for communication in the brain. When it was absent, male mice mounted other male mice more frequently and lost interest in females.
Apart from these examples, other studies show that there are many genes that seem to influence mate choice. Scientists have studied thousands of pairs of twins and found there is a strong genetic component, but that this is not the only cause; family and society play a role, while prenatal environment, peer groups and a person’s own sexual experiences play a significant role.
So next time someone claims that homosexuality is unnatural, just point him or her towards the nearest giraffe.