You need your eyes to see and your thumbs to help you hold things.

But what’s your clitoris for?

And why do women have orgasms anyway?

In men, the pelvic contractions of the orgasm help “jet-propel” sperm up inside the female body, to increase the chance of pregnancy. But women don’t need to have an orgasm to get pregnant.

In fact, depending on the study you check, only 20% of women have orgasms from penis-in-vagina sex at all. Partly it’s anatomy: your clitoris is outside the vagina.

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So what’s going on with that?

This week researchers at Yale University came up with a new theory: way back in the past we needed an orgasm to trigger ovulation.

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“Female orgasm seems to be an afterthought of our evolutionary past,” said a statement from Yale biologists Gunter Wagner and Mihaela Oavlicev of Yale University, co-authors of the study published in the Journal Of Experimental Zoology.

The team studied research papers on the evolution of ovulation in different kinds of mammals – animals who give birth to live babies.

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They found females in many mammal species release the hormones prolactin and oxytocin when they ovulate (release an egg to be fertilized). When human women have an orgasm, we also release these hormones into our blood.

“We interpret this evidence to suggest the physiological changes caused by human female orgasm are homologous (similar) to those that cause ovulation in other species,” concluded the study. “Human female orgasm is an evolutionary holdover from induced ovulation.”

The clitoris used to be inside the vagina

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In other words 60-65 million years ago, our female mammal ancestors needed sex with a male to ovulate.

To make this process easier, way back then the clitoris was inside the vaginal canal, where it could be stimulated by the penis.

Even today, some mammal species, such as rabbits and camels, only release an egg after they have mated with a male – although no one knows if they have orgasms.

This ovulation-after-sex method works well for animals where males and females live separately and only meet to mate. No sense releasing an egg if there’s no male around to fertilize it, right?

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When our ancestor mammals mated, the clitoris could send signals to the brain, triggering hormones that released an egg. Once the egg became fertilised, the same hormones may have helped it implant properly in the uterus or womb.

Living together means less orgasms

But eventually some mammals – especially primates like humans, apes and monkeys – started living together in groups. Females had access to regular sex, and didn’t need to save eggs carefully. In primates like us ovulation became spontaneous – we released an egg every month or so, with or without having sex.

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Along with this, the layout of the female genitals also started to change. In many animals the clitoris is still inside the vaginal canal. But in primates like humans, the clitoris is now sitting loud and proud outside the vagina. And to be frank… no one is sure why.

Cuddle hormones and bonding

Of course, human babies are way more complicated that young rabbits – babies take years of intense time and effort to raise properly. So maybe the pleasure of orgasm helps you bond with your mate to make raising kids easier?


After all, oxytocin and prolactin are also called the “cuddle hormones” because they help you feel close to someone. Humans release the same hormones when we cuddle with people we love, and breastfeeding mothers also release these hormones into their milk, to help them bond with their baby.

As Michaela Oavlicev puts it, “Female orgasm did not evolve in the human lineage, but may have acquired additional roles.”

David Puts, an evolutionary anthropologist at Pennsylvania State University puts it more plainly. “My gut instinct is that something that matters so much at an emotional level – the intense pleasure of orgasm – would seem to have reproductive consequences.”

Or… maybe not. In 2005 Elisabeth Lloyd, a philosopher at Indiana University published The Case of the Female Orgasm where she reviewed 18 scientific theories about the female orgasm. She couldn’t find any physical reason. Her theory is the Big O may just be a leftover from when we needed to come to produce an egg. Maybe it’s like how human males still have nipples as an evolutionary leftover?

Whatever the reason, we’re just happy the female orgasm is still around.

Text: Tara Barker