Research Uncovers Evolutionary Significance of Self-Pleasure

Evolutionary biologists have traced the origins of masturbation to pre-ancient primates around 40 million years ago. Recent research suggests that this practice served important evolutionary functions, such as protecting males from sexually transmitted infections (STIs) and enhancing fertility.

The study reveals that primates engage in masturbation more frequently than other animal species, indicating it is an older behaviour than previously believed. Dr. Matilda Brindle, the lead author from University College London, stated, “Our findings illuminate a common yet poorly understood sexual behaviour and mark a significant advancement in our understanding of masturbation’s functions.”

The research supports the idea that masturbation can increase reproductive success while also acting as a protective measure against STIs. Dr. Brindle noted that historically, masturbation was often viewed as either pathological or merely a by-product of sexual arousal, with past observations being too fragmented to fully comprehend its evolutionary significance.

To conduct this study, the team assembled the largest dataset on masturbation to date, incorporating nearly 400 sources, including 246 academic papers and 150 questionnaires from primatologists and zookeepers. This comprehensive data collection enabled the researchers to map the occurrence and evolution of masturbation across various primate species, identifying its presence in both males and females.

The findings suggest two primary adaptive functions for male masturbation: enhancing reproductive success and reducing the risk of STIs by cleansing the genital tract. Previous studies have indicated that increased masturbation may improve male sexual performance, enhance orgasm quality, relieve stress, and eliminate potentially cancerous prostate cells. For females, masturbation is linked to improved mood, heightened libido, and relief from menstrual cramps.

Dr. Brindle explained, “Masturbation has a long evolutionary history among primates, likely present in the common ancestor of all monkeys and apes, including humans.” However, many aspects of this behaviour remain unclear. Although evidence suggests a resemblance to gibbons in the common ancestor, definitive fossils have yet to be discovered.

The study also examined the ‘postcopulatory selection hypothesis,’ which posits that masturbation aids in successful fertilisation. This may occur in multiple ways: first, through masturbation without ejaculation to increase arousal before mating, particularly advantageous for low-ranking males who might be interrupted during copulation. Second, ejaculation during masturbation allows males to expel subpar sperm, leaving higher-quality sperm available for mating.

Furthermore, the research indicates that male masturbation has co-evolved with multi-male mating systems characterized by heightened competition. The ‘pathogen avoidance hypothesis’ further suggests that male masturbation helps prevent STIs after copulation by clearing the urethra, a primary infection site.

While the importance of female masturbation remains less understood, Dr. Brindle emphasized the need for more data on female sexual behaviour to fully grasp its evolutionary role. She concluded, “More research on female sexual behaviour is essential to better understand the evolutionary significance of masturbation.”