Same-Sex Behavior in Rhesus Macaques

• 09 Aug 2023

Source: TH

Why in News?

A recent study conducted by researchers from Imperial College London, titled "Genetics, Social Environment and Evolution of Male Same-Sex Behavior in Rhesus Macaques," has challenged conventional beliefs about same-sex behaviour (SSB) in animals.

• The engagement of animals in SSB has been considered a ‘Darwinian paradox’: if reproduction is critical to evolution, then SSB – which is non-reproductive – should have ceased to exist.
• This recent study found that male SSB in rhesus macaques is very common and doesn't harm evolution.

What are the Key Findings from the Study?

• Male Same-Sex Behavior (SSB) in Monkeys:
  • The study focuses on male same-sex mounting behaviour observed in rhesus macaques, a common monkey model, in Cayo Santiago, an island east of Puerto Rico.
    • 72% of observed male rhesus macaques engaged in same-sex mounting.
    • Only 46% participated in different-sex mounting.
  • It challenges the notion that SSB contradicts principles of evolution due to its non-reproductive nature.
• Role of Non-Genetic Factors:
  • The study considers external factors like social interactions and the environment.
  • These non-genetic elements contribute to the expression of SSB behaviour in male rhesus macaques.
    • SSB-engaging monkeys form coalitions against common enemies.
    • Male SSB could serve as a form of emotional communication and regulation.
• No Trade-off with Reproductive Fitness:
  • The study disputes the assumption that SSB reduces reproductive opportunities, as sexually active males engage in both SSB and different-sex sexual behaviour (DSB).
  • There is no direct correlation between SSB engagement and reduced offspring count in the macaque population.
• Future Research:
  • Female SSB and other monkey species require further investigation to broaden understanding.
  • The findings cannot be directly extrapolated to humans due to cultural and social influences.