Ian Kerner, a sexuality counselor and New York Times best-selling author, blogs about sex on Thursdays on The Chart. Read more from him on his website, GoodInBed.

What do female orgasms and male nipples have in common? It’s a question that is helping inform research into the purpose of female orgasm (other than simply as a form of pleasure).

Investigators want to know whether the female orgasm is an “adaptation” or “byproduct” of evolution. In other words, does the female orgasm, like the male orgasm, have its own evolutionary raison d’etre and contribute directly to reproductive success? Or is it just an awesome bonus? Make that totally awesome.

This question of whether the female orgasm is an adaptation or a byproduct came to the fore in 2005 with the publication of “The Case of the Female Orgasm: Bias in the Science of Evolution,” in which Indiana University professor Elisabeth Lloyd rigorously examined 21 theories that sought to promote the female orgasm as an adaptation and, ultimately, found all of them lacking.

Over the years, I’ve been lucky enough to have had some thought-provoking conversations with Lloyd on various topics – such as whether premature ejaculation makes good evolutionary sense – and recently, her work has been once again garnering much-deserved attention.



· One such theory involves “pair bonding,” the idea that orgasm bonds a couple emotionally so that they’re more likely to pursue parenthood.

· Another theory states that female orgasm is a part of mate selection: A woman will choose her mate based on his ability to bring her to climax.

· And a third main theory involves the belief that the contractions of female orgasm will draw sperm up the reproductive tract and into the uterus.

In her book, Lloyd argues that studies show that the vast majority of women do not experience orgasm as a result of intercourse alone, or do so inconsistently, so how could the female orgasm be an adaptation? If the female orgasm, like the male orgasm, was essential to the propagation of humanity, wouldn’t it need to occur consistently via sexual intercourse?

Instead, Lloyd argues to view the female orgasm through the lens of the “byproduct” theory, which holds that orgasm is a trait that is so heavily selected in males (reproduction wouldn’t happen without it) that women retain an inherent capacity – after all, men and women are physiologically the same during the first eight weeks of gestation: Penises grow out, clitorises grow in, but they share the same organic structure and tissue.

According to Lloyd, “It is crucial to note that the penis and the clitoris are the ‘same’ organ in men and women. ... [T]he nervous and erectile tissues involved in orgasm in both sexes arose from a common embryological source.”

This same byproduct theory also explains why men have nipples: The biological necessity of nursing our young makes the nipple so highly selected in women that male embryos develop immature structures as an evolutionary byproduct. Similar to the clitoris, the male nipple contains highly sensitive tissue that contributes to male sexual arousal and pleasure. Male nipples: arousing? Yes. Necessary? No.

Yet a study of twins and siblings published recently in the journal Animal Behavior questions the byproduct theory of female orgasm. Researchers looked for similarities in orgasm function between 10,000 Finnish female and male twins. And although there were significant similarities between same-sex twins, the researchers found no such correlation in orgasm function between opposite-sex twins, a correlation one would expect if female orgasm is a byproduct of male orgasm.

All this debate of adaptation vs. byproduct shouldn’t really matter to the average person who just wants to enjoy orgasms. The problem, though, is that we tend to believe that what’s “natural” is better, even orgasms. And if we do argue that the female orgasm is some sort of “evolutionary norm,” then what should be said of all the women who do not orgasm consistently – that they are somehow not normal?

As a sex counselor, I frequently receive e-mails from women who are unable to achieve orgasm via intercourse and wonder, “What can I do to change this? What’s wrong with me?”

Well, if we stop thinking of female orgasms as something that should naturally result from intercourse, then we can also stop feeling that there’s one right way to have orgasms. In this sense, the byproduct theory offers a more expansive and encompassing view of female sexuality.

Unfortunately the term “byproduct” doesn’t exactly resonate with a sense of the exalted, so perhaps we should stick to Lloyd’s later rephrasing of the female orgasm as a “fantastic bonus” – or as I like to say, totally awesome!