Male primates love spanking the monkey, and it may not just be for fun

Embargoed until: Publicly released: 2023-06-07 09:01

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The whole animal kingdom enjoys one off the wrist from time to time, but primates are particularly prolific pickle ticklers. Why this love of self-love evolved has remained mysterious, as it would seem, by definition, to exclude reproductive partners, leading to fewer offspring. But UK researchers who charted the evolutionary history of onanism across 105 primate species say they think they may have the answer, at least for males - indulging in a bit of bishop bashing may expel inferior sperm, improving the chances of fertilisation when sex does occur, and also clear out any sexually-transmitted pathogens from the males' urinary tracts. They say the higher prevalence of a spot of salami slapping among primate species in which one female mates with several males, and when sexual diseases are common, support their conclusions. The team also found that we primates have been enjoying a menage à moi since our distant evolutionary past.

Media release

From: The Royal Society

The evolution of masturbation is associated with postcopulatory selection and pathogen avoidance in primates

Masturbation occurs across the animal kingdom, but is particularly common in primates, including humans. But why would a behaviour that, by definition, excludes reproductive partners have evolved? We explore the evolutionary history of masturbation for the first time, showing that it is an ancient trait within the primate order. We find support for two potential adaptive functions of masturbation in male primates, suggesting that masturbation may a) increase reproductive success, and b) reduce the chance of contracting STIs by cleansing the genital tract. Together, our findings help shed light on a very common, but little understood, sexual behaviour.

Macaque-sturbation – Why is masturbation so common in primates? Research using the largest dataset of masturbation occurrence assembled to date suggests ‘autosexuality’ is an ancient trait in primates. It found evidence that masturbation evolves, and persists, more frequently in multi-male mating species, and in the presence of pathogens – where it may prevent infection by cleansing the genital tract. This suggests masturbation is unlikely to be just a by-product of high sexual arousal. (Images available) Proceedings of the Royal Society B.