In the years that Londa Schiebinger has been teaching a class on sexuality at Stanford, she has noted that “most” of her male students “can tell you the length and diameter of their penis, both flaccid and erect.” Meanwhile, her female students tend to have “no idea” how big their clitoris is, nor of the variation in size of the clitoris among women. When the magazine Science published an article titled “How Big Is the Average Penis?” in 2015, it remained among the most popular articles on their website for months.

(The answer, based on a review of seventeen studies of 15,521 males worldwide, was an erect 5.1 inches [13.1 cm] long and 4.6 inches [11.7 cm] around. Not that it matters. Unless it does.) Less known is that the average clitoris is not so far from that size. That fact is less important to Schiebinger than the fact that most people don’t know it.

In the sixteenth century, when the world was busy building phalluses in every major city, the famed French anatomist Ambroise Paré would reference the clitoris only as the “obscene part.” His contemporary, Italian surgeon Realdo Colombo, claimed to have discovered the clitoris, in much the same way that European traders discovered the long-inhabited American continent. Colombo called the clitoris “the seat of women’s delight,” likening it to a tiny version of the penis. That perspective would be propagated for centuries and is still found in embryology lessons today.

Schiebinger considers this a perfect example of the way a culture can inadvertently create ignorance. Both males and females know more about male than female anatomy; societies keep it so. Clitoral agnotology.

It was not until 1971, during the women’s liberation movement, that a group of women in Boston compiled the reference book Our Bodies, Ourselves to serve as “a model for women who want to learn about themselves, communicate their findings with doctors, and challenge the medical establishment to change and improve the care that women receive.”

The book is still in print in many languages, spreading worldwide the knowledge that the clitoris is more than a prehensile penis (as had been reported by the researchers Virginia Johnson and William Masters just a few years earlier), but a distinct organ composed of the glans (the part described by Colombo, akin to the head of the penis) as well as the much larger shaft and crura, extending beneath the vulvar skin.

So it is not possible to measure one’s own clitoris, and to know a true average clitoris size would require access to many corpses. Even then it would be difficult because the clitoris is largely spongy tissue that engorges with blood when aroused, like the penis, so it is best studied in arousable bodies.