Discover! >> A New Science Study Is Trying To Explain Why Homosexuality Evolved

A new study has shed light on homosexuality, and why it might have evolved.  From dolphins to chimpanzees, same-sex behaviours (SSBs) are common among thousands of animals, but until now, why they might be beneficial has remained unclear.

Now, experts at Imperial College London have revealed how primates show more SSBs when their habitats are harsh or dangerous, and when their social groups are larger and more complex.  This suggests homosexuality might help forge strong bonds that allow groups to stay together to survive harsh conditions, according to the experts.

For example, if predators are especially common, a tight-knit social group that can trust each other’s alarm calls is a survival advantage.

‘Our findings suggest that SSB is widespread rather than rare and that it has likely evolved multiple times across primate lineages, in part as a way to navigate complex social and environmental systems,’ co-author Professor Vincent Savolainen told the Daily Mail.

However, he cautioned that the findings don’t make any direct claims about the evolution of homosexuality in humans. ‘It highlights several promising directions for future research by anthropologists and psychologists interested in the evolutionary and social contexts of same-sex behaviour,’ he added.

In the study, published in the journal Nature Ecology & Evolution, the researchers analysed existing research looking at 491 species of non-human primates – 59 of which engage in same-sex behaviours.

Previously, researchers have suggested that these behaviours in primates might be driven in part by genetic factors. For example, in 2023, Professor Savolainen found that SSB was about 6.4 per cent heritable in rhesus macaques – meaning that a tendency towards homosexuality could be passed down genetically. However, this leaves a lot of room for other factors to determine whether SSB actually occurs and a lot of uncertainty over what those causes might be.

The new analysis supports the idea that homosexual behaviour in primates is largely driven by environmental and social factors, rather than genes alone. Among the animals where SSB is observed, the behaviour is more common when the species faces a drier environment, scarcer resources, or a lot of predators.

It is also more common among species with complex social systems, a greater size difference between males and females, and those with longer lifespans. Based on these insights, Professor Savolainen suggests SSB ‘probably’ evolved as a survival strategy to help highly social species survive environmental challenges.

This study adds to a growing body of research suggesting that homosexual behaviour is significantly more common in non-human species than previously thought.

Scientists have now observed SSB in over 1,500 different species, ranging from primates like chimpanzees to dolphins and ducks.