Scientists have finally worked out why women have orgasms - and it’s all thanks to monkeys.For years, researchers have wondered why exactly the female orgasm exists. It plays no part in reproduction and is functionally redundant, unlike in many other animals.But scientists now say that the experience is an afterthought of evolution, left from our ape ancestors.In many mammals, the male starts ovulation by sexually stimulating the female and leading her to become fertile. But in humans that link has been lost, since the clitoris shifted from inside the vaginal canal to the outside, which at the same time appeared to remove the link between orgasms and reproduction.Scientists have been puzzled because there doesn’t appear to be any association between the orgasm and whether sex leads to reproduction or the number of children that might be conceived. So the scientists instead explored the hormones that are released during the act - and found that those same hormones play an important role in ovulation in many other mammals.That led the researchers to believe that the trait now called the orgasm had another function in the past, helping trigger ovulation.‘Prior studies have tended to focus on evidence from human biology and the modification of a trait rather than its evolutionary origin,’ said Yale Biology Institute researcher Gunter Wagner.But the scientists say that it is important to note that the evolutionary ancestor of the climax isn’t necessarily the same as it looks today.‘It is important to stress that it didn’t look like the human female orgasm looks like now,’ said Mihaela Pavlicev, who helped lead the study. ‘We think that [the hormonal surge] is the core that was maybe modified further in humans.’But the research worked by identifying the surge itself, rather than the thing that’s now known as the orgasm. It is often difficult to find the same trait in different species because they change with time, but by identifying the surge they could track it through history.‘We think the hormonal surge characterises a trait that we know as female orgasm in humans,’ Pavlicev said. ‘This insight enabled us to trace the evolution of the trait across species.’