Female orgasm is a topic shrouded in mystery – not just for sexually awkward boyfriends, but for biologists too. We know, for example, that lots of animals have clitorises, yet a surprising number of female mammals don’t seem to experience orgasms at all.

This has led researchers to some new discoveries and debates – and some intriguing new theories – about the “what,” the “when,” and the “why” of the female orgasm.

At first glance, the “why” might seem like the easiest question to answer: We have orgasms because they feel great. But from an evolutionary perspective, the answer isn’t so obvious. Sure, it makes sense for male orgasms to feel great, because males who have lots of orgasms can produce lots of children – but a female doesn’t need to have an orgasm to fertilize her eggs. In fact, it’s in her genes’ best interest for her to fight off most of the sexual advances she gets, so she doesn’t end up carrying the offspring of some random loser.

When we look at what some of the things that happen in a woman’s body during orgasm, though, we start to find some clues about how sexual pleasure actually does help her select mates. For example, the muscle contractions involved in a woman’s orgasm help push sperm up into the uterus – while some studies have found that similar contractions can push sperm away from the uterus if a woman isn’t a huge fan of her partner. In other words, orgasm, or lack thereof, may be a way for women’s bodies to instinctively accept or reject a mate.

Some researchers think another part of the answer may actually lie in male anatomy. For example, in her book “The Case of the Female Orgasm,” Elisabeth Lloyd argues that because male and female sexual anatomy is so structurally similar (the clitoris, for example, is almost identical to the head of the penis), women can have orgasms – essentially – because men can.

It’s a view that’s taken a lotta heat, in both the mainstream press and the scientific community. One counter-argument that’s been gaining traction says that if female orgasm is directly related to male orgasm, we should expect to find very similar orgasmic function in genetically similar opposite-sex pairs – twins, for example – but no one’s yet been able to find any such correlation. In fact, one recent study found that while same-sex twins do share similar orgasmic function, opposite-sex twins don’t. But then again, that study has been criticized for using self-reported data, which means the jury’s still out on that particular angle of the debate.

Another recent self-reported study, by Brendan Zietsch of the University of Queensland and Pekka Santtila of Finland’s Abo Akedemi University, seems to deepen the mystery even further. Zietsch and Santtila found that the ability of a particular woman to have an orgasm doesn’t seem to have anything to do with…well, with much of anything, apparently:

We found zero to weak phenotypic correlations between all three orgasm rates and all other 19 traits examined, including occupational status, social class, educational attainment, extraversion, neuroticism, psychoticism, impulsiveness, childhood illness, maternal pregnancy stress, marital status, political liberalism, restrictive attitudes toward sex, libido, lifetime number of sex partners, risky sexual behavior, masculinity, orientation toward uncommitted sex, age of first intercourse, and sexual fantasy. Furthermore, none of the correlations had significant genetic components.

In short, a woman’s orgasm ability doesn’t appear to be statistically correlated with her psychology, financial status, sexual behavior – or even her genes. Looks like we may still be a long way from understanding what makes some women more orgasmic than others.

Maybe some of those women could try ritually appeasing Aphrodite – ya know, in the interest of Science and all.

On the other hand, the question of “when” – i.e., when in our evolutionary history female orgasm became important – may provide some interesting clues to the “what” and “why” puzzles.

Some biologists claim that certain female mammals – pigs and several monkey species, for example – don’t experience orgasm at all. Debates about these questions continue to rage, though, because the definition of female orgasm can be hard to pin down in other species. We can’t exactly ask a gibbon, “Was it good for you?” so we’re left with a hodgepodge of techniques – mostly analyses of vocalizations and other behavioral indicators.

Meanwhile, Concordia University neurochemist Jim Pfaus has found that female rats’ brains respond to clitoral stimulation almost identically to the way human brains do (in answer to your burning question, Pfaus and his grad students pleasure their lady rats with little paintbrushes). And since even reptiles like crocodiles have clitorises, it seems likely that female sexual pleasure – at least, from clitoral stimulation – was hard-wired into vertebrate brains long before mammals even existed.

Since animals with such different bodies seem to respond so similarly to sexual pleasure, what exactly constitutes a female orgasm may depend on a species’ biology – and maybe even on the individual female – more than any hard-and-fast definition can easily accomodate. As just about any woman will tell you, no two women are alike when it comes to sex – and that actually hints at a profound idea about female sexual pleasure: Unlike in males, it’s not so much an incentive to just have sex period, but to have it with the right partners in the right ways.

So if you’re a woman, be proud of your pickyness – it’s built into your biology. And if you’re a sexually awkward boyfriend… well, just remember that learning what she likes is a big part of the fun.