A ground-breaking study by scientists from Imperial College London – “Genetics, Social Environment, and Evolution of Male Same-Sex Behavior in Rhesus Macaques” – has brought new insights into same-sex behaviour (SSB) amongst animals, particularly challenging the long-held belief that it contradicts evolutionary theory. This research sheds light on how frequent SSB is in male rhesus macaques and how it doesn’t interfere with evolution.
Unraveling Male Same-Sex Behaviors in Monkeys
The researchers focused their study on male SSB mounting behaviors observed in rhesus macaques – commonly used in monkey-related studies – from Cayo Santiago island, located East of Puerto Rico. The findings were surprising: 72% of the observed male macaques engaged in SSB, a much higher percentage than those involved in different-sex behavior, at only 46%. The research seems to challenge the commonly held belief that SSB should disappear due to its non-reproductive nature and the Darwinian principle that natural selection favors traits beneficial for reproduction.
The Significant Role of Non-Genetic Factors in SSB Expression
Going beyond genetics, the researchers also turned their attention to external influences such as the immediate environmental conditions and social interactions. They discovered that these non-genetic variables significantly contribute to the exhibition of SSB in male rhesus macaques. For instance, it has been observed that macaques engaging in SSB tend to form coalitions against common adversaries. Also, SSB in these monkeys might function as emotional communication and regulation.
No Detrimental Impact on Reproductive Fitness Found
The study’s findings defy the conventional notion that SSB negatively affects reproductive opportunities. It was revealed that sexually active male macaques are likely to engage in both SSB and different-sex sexual behavior (DSB). Furthermore, the research showed no direct correlation between SSB engagement and a decrease in the offspring count within the macaque population. This finding contradicts the assumption that SSB should be disadvantageous from an evolutionary standpoint.
Looking Towards Future Investigations
Further exploration is needed to understand the complex nature of SSB behavior, particularly in other monkey species and female SSB. Despite these new discoveries about SSB in rhesus macaques, the researchers warn against drawing parallels to human behavior, as the influence of social and cultural factors on human sexual behaviors is significantly different.
This study represents a significant leap forward in our understanding of SSB in animal populations, especially among male rhesus macaques. Its findings have not only challenged traditional beliefs but also opened up new areas for future research. Although more probing is required, the research forms a crucial foundation for analyzing SSB in animals and contributes to evolving conversations about natural sex behaviors and their relationship with genetic and non-genetic influences.
