The evolutionary origin of female orgasm

I must admit to an internal debate on whether or not to post this piece on Meg Ryan Syndrome – otherwise known as female orgasm – until I saw that the second author on the paper in the Journal of Experimental Zoology was Gunter Wagner – a professor at Yale who has already made a number of visionary contributions to reproductive medicine. Wagner and lead author Mihaela Pavlicev have found one dominant theory – that female orgasm arose as a fortunate byproduct of male orgasm that accompanies sperm transfer – unsatisfactory. They have trawled through many mammalian species, from humans and other primates, through a range of mammals including woodchucks, dolphins and Bactrian camels, down to aardvarks and koala bears, to discover which species are typified by induced ovulation, where copulation is needed to trigger ovulation, and which are typified by spontaneous ovulation, where eggs are released at a certain point in every ovulatory cycle regardless of copulation. They then correlated the distance of the clitoris from the copulatory canal with each form of ovulation.

Their main point is that induced ovulation is an ancestral trait where a pronounced copulatory hormonal surge accompanies ovulation and is necessary to command the ovary to release its eggs. This hormonal surge is similar to that experienced by women at the point of orgasm but where it is no longer needed for ovulation to occur. They noticed that induced ovulators tended to have the clitoris positioned inside or very close to the sex canal/vagina because it is essential for copulation to stimulate it in order for the hormonal surge and ovulation to ensue. Spontaneous ovulators are released from this necessity and this is why they found that spontaneous ovulation is associated with increasing distance of the clitoris from the vagina. Which could explain why Meg Ryan’s behaviour in the restaurant was the envy of her fellow female diners – “I’ll have what she’s having!” Orgasm in human females can be a bit of a hit or miss affair because it cannot be guaranteed by penetrative sex.

The publication of the J. Exp. Zoology paper is accompanied by a very readable piece by Nicola Davis in The Guardian newspaper.