Scientists have found a clue to one of the great mysteries of sex - why the female orgasm ever evolved.
Researchers now believe that the orgasm is an ‘evolutionary gift’ from older lineages of animals that only ovulate during sex.
The response necessary for ovulation in animals such as rabbits was preserved in humans, the scientists believe.
Yale University’s Gunter Wagner said: “It is not a reproductive feature but another, the significance of which we still need to understand.”
Researchers injected rabbits with fluoxetine, an anti-depressant known to reduce the ability to achieve orgasm.
They found that rabbits treated with the drug ovulated 30 percent less, hinting that there was a biological link between copulation-induced ovulation and the female orgasm.
Wagner said: “This is important to our understanding female sexuality.”
In rabbits, cats, and ferrets, the clitoris is located in the reproductive tract and spurs the release of hormones necessary to stimulate ovulation.
The hormones are the same as those released during orgasm in human females, but they have nothing to do with timing of ovulation or reproduction in humans.
This reflex no longer plays a role in reproduction, and female genitalia was rearranged in humans and some other species, but the orgasm appears to be an evolutionary holdover, the researchers said.