Their new findings suggest it could serve an important role in evolution.
An ancient trait in primates, masturbation — at least for the males of the species — increases their reproductive success while also helping them avoid catching sexually transmitted infections (STIs), investigators from University College London discovered by using a huge set of data on primate masturbation.
Information came from nearly 400 sources, including 246 published academic papers, as well as 150 questionnaires and personal communications from primatologists and zookeepers.
The investigators used this data to track masturbation habits among primates, to better understand it. They discovered that masturbation has a long evolutionary history in primates. It was even most likely present in the ancestor that all monkeys and apes, including humans, share.
The research team came up with several ideas for why evolution would involve something that seems as non-functional as masturbation.
They proposed that masturbation helps with successful fertilization, increasing arousal before sex, which could be helpful for low-ranking males who might be interrupted quickly.
The study authors also suggested that masturbation with ejaculation could help shed substandard semen, leaving the better swimmers for when they actually have something to fertilize.
The researchers found support for this hypothesis, showing that male masturbation evolved along with mating systems where there were multiple males and a lot of competition.
The authors also proposed that male masturbation could reduce the chances of contracting an STI by cleansing the urethra with ejaculate. The team also discovered evidence supporting this idea.
What they didn’t find was much evidence on the significance of female masturbation, because there are simply fewer reports describing it.
The study was published June 6 in the Proceedings of The Royal Society B journal.
“Our findings help shed light on a very common, but little understood, sexual behavior and represent a significant advance in our understanding of the functions of masturbation,” said Dr. Matilda Brindle, of UCL's department of anthropology.
“The fact that autosexual behavior may serve an adaptive function, is ubiquitous throughout the primate order, and is practiced by captive and wild-living members of both sexes, demonstrates that masturbation is part of a repertoire of healthy sexual behaviors,” Brindle said in a university news release.
The U.S. Centers for Disease Control and Prevention has more on sexual health.
SOURCE: University College London, news release, June 6, 2023