Only three things are certain in life: death, taxes, and the existence of gay animals. 

Same-sex sexual behaviour has been observed in more than 1,500 animal species, from penguins to dolphins to sea urchins to scarab beetles. Male field crickets, for example, often perform mating songs and dances for each other, and the majority of male macaque monkeys are bi kings.

As much as I am an unreserved, committed ally to every single queer animal on earth (even the two penguin dads who kidnapped a straight couple’s baby), the prevalence of LGBTQ+ creatures does beg the question: why and how are there so many gay animals? How does this tally with Darwin’s theory of evolution, when same-sex relationships in the animal kingdom don’t directly aid reproduction?

Some researchers have proposed that LGBTQ+ animals are simply born this way and have been knocking around since the dawn of the animal kingdom. But the authors of a new study published this week on thousands of mammalian species have suggested that same-sex sexual behaviour began appearing in mammals when they started living in social groups.

The researchers explained that although same-sex relationships between mammals do not produce offspring, they can offer other evolutionary advantages, such as smoothing over conflicts. “It may contribute to establishing and maintaining positive social relationships,” Dr José Gómez, an evolutionary biologist and an author of the new study, told the New York Times.

The researchers surveyed 6,649 species of living mammals, noting which species had been observed engaging in same-sex sexual behaviour, which they defined as anything from courtship to mating to forming long-term bonds. Out of the thousands surveyed, 261 exhibited same-sex sexual behaviour.

The researchers then investigated how the behaviour arose in mammals. By examining an evolutionary tree, they discovered that the gay species were scattered across the tree’s branches, suggesting that same-sex sexual behaviour arose independently in each species. When Dr Gómez and his colleagues looked for shared traits between these queer species, they realised that the majority were social species instead of solitary ones.

While social species benefit from better protection from predators, they’re also likely to form ‘hierarchical’ groups in which more dominant animals attack more submissive animals within the group. These sorts of conflicts can cause groups to become divided, which can cause issues for the entire unit. The researchers suggested that same-sex sexual behaviour might be one of the ways that mammals can minimise conflict in their unstable groups, by allowing them to form bonds and alliances.

Dr Gómez also warned that the study did not reveal anything about sexual orientation in humans. “The type of same-sex sexual behaviour we have used in our analysis is so different from that observed in humans that our study is unable to provide an explanation for its expression today.”