Scientists have finally solved the age-long mystery behind female sexual pleasure. Thanks to monkeys, they discovered that the female orgasm once played a part in inducing ovulation.
For decades, scientists have wondered why exactly women orgasm, since it plays no part in reproduction and is practically unnecessary, unlike in numerous animals.
The secret lies in ovulation, the process that prompts ovaries to release eggs for reproduction. In some species, like rabbits and cats, physical stimulation is needed to cause the egg to be discharged – an occurrence known as induced ovulation. But in humans, ovulation occurs spontaneously (without stimulation), often on a regular schedule. And not only can women come to orgasm without penetration, but a recent survey of more than 1,000 women suggests that many – about 61.6% of heterosexual women – do not orgasm during copulation at all. Nor is female orgasm linked with a higher number of human babies.
The topic has long baffled scientists, who in the past came up with two hypotheses. One school of thought is that women do need orgasms to reproduce, but scientists have not yet figured out why. Others see orgasms as happy misfortunes linked with the clitoris, the organ responsible for female sexual arousal that is sometimes thought of as the female version of the male penis.
Last week, the authors in the Journal of Experimental Zoology, surmised that the response initiated in mammals more than 150 million years ago as a process of releasing eggs to be fertilized after sex.
“For orgasms, we kept it reserved for humans and primates,” said Mihaela Pavlicev, an evolutionary biologist at University of Cincinnati College of Medicine and an author of the new study.
“We didn’t look to other species to dig deeper and look for the origin,” she adds.
To see whether orgasm’s evolutionary predecessor was induced ovulation – in a similar way that fins were ancestral to limbs – she and Gunter Wagner, an evolutionary biologist from Yale University, first needed to see whether induced ovulation predated spontaneous ovulation in the history of evolution.
Evolutionary biologists have never wrangled over male orgasm since the pleasure is obviously linked to ejaculation – the most crucial step in transferring of a male’s sperm to the female reproductive tract. That pleasure experienced by men encourages them to deliver more sperm, which works for the benefit of evolution.
An orgasm is the sudden release of amassed sexual excitement during the sexual reaction cycle, resulting in rhythmic muscular convulsions in the pelvic region distinguished by sexual pleasure. Orgasms are experienced by both men and women and are controlled by the involuntary or autonomic nervous system. Often, an orgasm may follow other involuntary acts, such as muscular spasms in various regions of the body, a general ecstasy and, commonly, body movements and seductive words or hissing noise.
In women, this fiery, blissful release of sexual tension is accompanied by contractions of the genital muscles. If a woman is continuously stimulated, she may experience multiple orgasms, while a small percentage of women may ejaculate – a clear fluid spurting from glands (known as Skene’s glands) located close to the urethra during extreme sexual arousal or during orgasm.
According to the new study, some animals like rats, also experience surge of hormones, including prolactin and oxytocin, because they need these chemicals to tell their body to ovulate. The surge can also help species like rodents to implant eggs.
Because of this hormone-orgasm connection in both humans and induced ovulators, Pavlicev believes that they were once linked long before humans became a species. She theorizes that that spontaneous ovulation possibly evolved in the last common ancestor of primates and rodents. But, eventually, they must have evolved into so-called spontaneous ovulators, but the hormonal reactions connected with orgasms remained.
By its very nature, researchers hypothesize the female orgasm may have once had a direct role in reproduction – in other words, it acted as a reflex to trigger ovulation. They suggest that this reflex evolved to become unnecessary; therefore, it is now simply a feeling of pleasure during sexual activity.
The researchers also point to study that compared genitalia across mammalian species with placenta. They say the clitoris also may have evolved. They believe the clitoris – the female’s most sensitive organ, which when stimulated, can induce orgasm – also evolved.
Based on the evolutionary links between an array of animals, the researchers found that later-evolving creatures, including humans, ovulated spontaneously. And this change coincided with the clitoris shifting northward, further away from the vagina. They say the clitoris was once located in the copulatory canal.
“At that point,” says Pavlicev, “the clitoris lost its function for reproduction.”
Her work raises even more fascinating questions such as, why did humans start ovulating spontaneously in the first place? Which came first: spontaneous ovulation or induced ovulation? And what sparked these changes in women?
Perhaps the most intriguing aspect of Pavlicev’s study is the suggestion that there is an evolutionary reason women don’t always orgasm.
“It’s not that there’s anything wrong,” she says. “It’s just how our anatomy is.”
It translates to – women who do not experience orgasm during sex are not faulty – just highly evolved.