For years, scientists have pondered the purpose of the female orgasm. Where did it come from? How did it happen? Unlike its male counterpart, the female orgasm is not necessary for sexual reproduction, so what is the point?
A new theory published in theJournal of Experimental Zoology proposes a possible evolutionary explanation. The study, called "The Evolutionary Origin of Female Orgasm," suggests that the female orgasm as we (hopefully) know it today may have evolved from a different function used by our ancestral predecessors millions of years ago—a function that actually was crucial for reproduction.
For women today, ovulation happens spontaneously once a month. But for many mammal species, including cats, rabbits, and ferrets, ovulation has to be induced, and this only happens when, during intercourse with a male member of the male species, stimulation causes hormonal surges in the body that result in an egg. This mid-coitus ovulation must happen in order for conception to occur. Researchers posited that the modern female orgasm may have evolved as a reflex to trigger a similar process, when human ancestors still procreated through induced ovulation.
"We looked at how the induced ovulation is distributed and inferred when the new trait evolved," Mihaela Pavličev, an author of the study, tells Broadly. "The two groups that have most spontaneous ovulation are rodents and primates, so we think it is probably their common ancestor that evolved the spontaneous ovulation, 70 to 75 million years ago."
There is also some physical evidence that supports the theory. For animals who have induced ovulation during sex, the clitoris is located inside the vagina. Human clitorises are located externally. This could be related to the evolution of the ovulation; it may be that, millions of years ago, clitoral stimulation was necessary to induce ovulation.
"We also looked at the anatomy of female genitalia and noticed at the time when spontaneous ovulation must have evolved, the clitoris was removed from the vaginal opening," Pavličev says.
However, Pavličev tells Broadly the history of these hormonal surges in induced ovulation are just one aspect of the female orgasm; there are also muscular reactions and neurological phenomena that warrant more study. There's also the fact that the clitoris is related to the male penis, and because the two body parts are related, the orgasms they produce may be linked. However, even these explanations do not fully answer why the female orgasm exists as it does today.
"We know the trait has been there before," she says, "so we're talking about why it originated. That's why we have to look at more than other primate species."
This evolutionary theory may not provide a complete answer to why the female orgasm exists today, but Pavličev says she hopes that looking at the evolutionary history of the process will provide new avenues for studying the function—and that it may, at the very least, help scientists think of new questions to ask getting off.