It's a question which has intrigued scientists for centuries – why do women have orgasms?
But a team of Yale researchers claim to have finally discovered the answer and it’s all to do with ovulation.
They believe that in the past, our female ancestors only released an egg after being stimulated by a male just before or during sex. This is still the case for numerous species of mammals – including rabbits, ferrets, camels and cats.
Once stimulated, the prehistoric female would have released certain hormones causing her to ovulate and the egg was then fertilised by sperm. But over hundreds of thousands of years their bodies evolved to ovulate by themselves – once a month.
This means a woman’s orgasm – famously simulated by Meg Ryan in When Harry Met Sally – now has no reproductive function, and this is what has baffled scientists.
Professor Gunter Wagner, who specialises in Ecology and Evolutionary Biology at Yale, believes that in the past all female mammals ovulated after having an orgasm. It was only later on that some species – such as humans, dogs, cows and rats – evolved to ovulate by themselves during cycles.
Professor Wagner, whose discovery is published in the journal JEZ-Molecular and Developmental Evolution, focused on the hormones released by different female mammals during sex. Most release a surge of the ‘feelgood’ hormones prolactin and oxytocin and in many cases this triggers ovulation.
This led him and his colleagues to believe that in the past, ovulation was always triggered by an orgasm.
Dr Mihaela Pavlicev of the Centre for Prevention of Preterm Birth at Cincinnati Children’s Hospital, in the US, who was also involved in the research said: ‘We think the hormonal surge characterises a trait that we know as female orgasm in humans. This insight enabled us to trace the evolution of the trait across species.
‘[Similar] traits in different species are often difficult to identify, as they can change substantially in the course of evolution.’ Other scientists have come up with other controversial explanations as to why women have orgasms when they perform no function.
One of the most obvious is that they simply encourage them to have more sex, and reproduce, as it is so enjoyable.
Another theory is that they create a stronger bond between the woman and the man, making it more likely they will stay together and have more children.
Finally, some scientists claim it is down to the ‘mate-choice’ hypothesis whereby females chose a mate on the basis of sexual satisfaction. Theoretically, a male which gives them a better orgasm has stronger sperm and will help her to produce more offspring. The Archive of Sexual Behaviour also found in a study that women who pretended to orgasm did so as part of a strategy of mate retention.
The study found women who thought that their partner was likely to cheat on them were more likely to fake it.