Under the warm seclusion of her own sheets, nearly every sexually healthy woman has experienced an orgasm, whether it be at the hands of a lover or her own. Women have been meeting the onrush of sexual desire with orgasms as far back into history as we know, but they have a long record of being suppressed in society. Today, men and women alike live in a world with vibrators, dildos, and do-it-yourself tips to reaching the ever-elusive climax. How did humans evolve to encourage such sexual pleasure?

For women, an orgasm is an intense, euphoric release of sexual tension. Once aroused, the genital muscles contract and can be repeatedly stimulated for a ripple effect of orgasms. According to the National Health Service, only a minority of women ejaculate during intense sexual excitement, a fact which continues to confuse sexual health experts today.

According to a study published in the journal Animal Behaviour, a woman’s orgasm does not definitively affect the reproductive success of intercourse. Meanwhile, a man’s orgasm leads to an ejaculation of gametes (sperm) that are designed to reach an egg within the woman’s body for reproduction. The prevailing theory is that by triggering pleasure centers, the contractions help direct the sperm and increase the chances a woman will want to engage in intercourse more often to improve the probability of pregnancy.

Early on, this simple, yet cunningly powerful physiological response to stimulation, was thought to be a key ingredient for a successful pregnancy. In the 13th century, the medieval belief was that a woman and man must both achieve orgasms to conceive a baby. This gave way to the female orgasm becoming an 18th century medical treatment for a condition diagnosed as “hysteria” — sexual frustration which drove a woman insane and required pelvic massages and douching to relieve.

But at that point, medical experts still did not believe women experienced pleasure or sexual desire, which is why masturbation was highly frowned upon. Female orgasms, then referred to as paroxysms, caused hysteria, which required “treatment” so doctors and midwives applied vegetable oil to the women’s genitals as they massaged them. In order to save medical professionals from achy, cramped fingers, English physician Dr. Joseph Mortimer Granville patented the first electromechanical vibrator in 1880.

Soon, electricity would open the doors for women to bring vibrators home. Movies were invented and soon after pornography was filmed and often starred a woman achieving orgasm, giving birth to society’s very slow, but steady acceptance of prioritizing women’s sexual pleasure.

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To learn how to improve the muscles that contract during orgasm, read about a first-timer’s experience with a vagina muscle trainer. Read here.