New study undermines the idea that masturbation is unhealthy or a result of sexual excitement. All primates—including humans—masturbate.

Masturbation is an old feature in monkeys that promotes reproductive success and decreases the risk of sexually transmitted illnesses in men.

400 sources, including 246 academic publications, were used to create the biggest primate masturbation database. Masturbation was found in the progenitor of all monkeys and apes.

Because of little evidence on lemurs, lorises, and tarsiers, it was unclear if their predecessors had the behavior.

Autosexuality’s development has been studied.

The researchers found evidence to support the postcopulatory selection hypothesis, which suggests that masturbation without ejaculation can boost arousal before sex and allow males to shed inferior semen to outcompete other males.

The pathogen avoidance theory suggests that masturbation with ejaculation cleanses the urethra and helps monkeys avoid sexually transmitted illnesses.

Fewer female masturbation studies made analysis difficult. Proceedings of the Royal Society B reported the findings. Matilda Brindle, the paper’s lead author, adds, “Our findings help shed light on a very common, but little understood, sexual behaviour and represent a significant advance in our understanding of masturbation’s functions.

Masturbation is part of a healthy sexual repertoire since it may have an adaptive role, is common across the primate order, and is practiced by captive and wild-living members of both sexes.