Photos by Peter Meciar and Nabi Tang via Stocksy

Many of the most eye roll–inducing arguments against the rights of women originate in the (ostensibly) fundamental, biological differences between the sexes. Women can't be president because they are too irrational on their periods. Women should be primary caregivers because the hormones in their boobs make them more nurturing. Rape culture is a natural byproduct of men's horniness and aggression and women's natural passivity. Our inferiority is supposedly written into our bodies, and always has been. Going back to the Victorian era, our delicate nerves were the reason we couldn't work. And in the Middle Ages, women were considered less bold and adventurous than men because their testicles were smaller and colder.

Until the 18th century, many doctors and philosophers assumed that humans only had one biological sex: male. Women were simply inferior men whose penises were flipped inside-out and tucked away in their bodies. Galen of Pergamon, one of the most influential physicians of the Ancient Roman world, was a big proponent of this theory. He believed that women were men whose genitals failed to "perfectly" develop in utero. "You can see something like this in the eyes of the mole," he wrote in the second century CE, "which have vitreous and crystalline humours and the tunics that surround these and grow out from the meninges, as I have said, and they have these just as much as animals do that make use of their eyes. The mole's eyes, however, do not open, nor do they project but are left there imperfect." In other words, he was saying that women are like moles.

Read more: Doctors Created Vibrators After Growing Tired of Masturbating 'Hysterical' Women

Thomas Laqueur calls this conception of biological sex the one-sex theory. His book, Making Sex: Body and Gender from the Greeks to Freud, explores how and when Western society shifted its thinking from a single "essential" sex to the binary model we use today. "Rather than there being opposite sexes, they were contiguous and hierarchical," he tells Broadly. "There was a hierarchy of gender and a continuum of bodies."

Men and women could move up and down the sex ladder by any number of behaviors and biological processes. For example, "someone having a nosebleed was [experiencing] nominally the same physiological process as menstruating," Laqueur says. Medieval medical texts also make mention of women who might become men at puberty, when their inverted genitalia finally dropped.

Pre-Enlightenment physicians also believed in the four humors: blood, yellow bile, black bile, and phlegm. All life forms possessed these four liquids in their bodies to varying degrees. Each humor was linked to an element, and was considered either wet or dry and hot or cold. Heat was associated with activity, and thus with men and their derring-do. Women were colder, and thus shittier, than men. The openness of the vaginal cavity was seen as a deficit of character: If their bodies are physically permeable, so are their minds/souls. But every person had hot and cold, open and closed, hard and soft, within them. It was a question of degree, which could also change based on age, the season, and time of day.

Watch: The History of Birth Control

So when and why did doctors move from one sex to two? Many scholars set the change during a time known as the "long 18th century": 1688-1815. This time period covers the Age of Enlightenment in Europe and the period of political revolution that followed. It was during this time that many ideas about man's inalienable rights were conceived.



Before the long 18th century, Western societies operated under feudalism, which presupposes that people are born unequal. Kings were better than lords who were better than peasants, and this sense of betterness extended to their physical bodies. "Aristocrats have better bodies, bodies are racialized," says Laqueur, summing up the idea. "The body is open and fluid and the consequence of a hierarchy in heaven." Specifics of this corruptible flesh are of less consequence than our souls. We were all servants in the Kingdom of Heaven, which set the hierarchy on earth.

Men are horny, therefore women must be the opposite of horny.

This idea of a natural hierarchy was challenged by the thinkers of the Enlightenment. We see it in the Declaration of Independence: All men are created equal. But it was also understood that women and people of color couldn't possibly have been created equal. Therefore, it became necessary to conceive of innate biological differences between men and women, white and black. "As political theorists were increasingly invoking a potentially egalitarian language of natural rights in the 18th century, 'woman' had to be defined as qualitatively different from men in order that political power would be kept out of women's reach," writes Karen Harvey in Cambridge University Press's Historical Journal.

Sexual difference becomes much more explicit in medical texts once women's anatomy gets its own words. We see this change happen between the first and second printings of a French doctor's treatise, The Diseases of VVomen with Child, And in Child-bed by Francois Mauriceau. In the first edition, printed in 1668, Mauriceau writes this:

Every Woman hath two Tefticles as well as Men, being alfo for the fame ufe, which is to convert into fruitful Seed the Blood that is brought to them by the Preparing Veffels...; but they differ from thofe of Men in feituation, figure, magnitude, fubftance, temperature, and compofition.

By the 1683 edition, Mauriceau's publishers seem embarrassed to include such outdated information. Mauriceau's editor includes a note saying he has made a "Miftake." Women have Ovaria, not Tefticles. The same organ is now understood to be completely different in men than in women. Never mind that ovaries and testicles do have structural and functional similarities—they provide genetic material for sexual reproduction in the form of eggs and sperm. What was once seen as similar enough was now branded as entirely distinct.

What follows in the long 18th century and into the Victorian era is a solidifying of masculine and feminine as diametrically opposed. When doctors followed humoral system, it was understood that everyone was a little hot, a little cold, a little country, a little rock and roll. Women were frequently represented as hornier than men. But once everyone has to be shunted into a binary, women are rendered passive and disinclined to sex. "Historically, women had been perceived as lascivious and lustful creatures," writes Ruth Perry in the amazingly titled academic paper "Colonizing the Breast." "[B]y the middle of the eighteenth century they were increasingly reimagined as belonging to another order of being: loving but without sexual needs." Men are horny, therefore women must be the opposite of horny.

For More Stories Like This, Sign Up for Our Newsletter

Nonbinary and genderfluid people of the 21st century can gain some comfort from the notion that sex and gender divisions weren't always so rigid. But that understanding is nevertheless tinged with the knowledge that the sexes, fluid though they were, were still ranked. Someone was still coming out a winner, and yet again it was whoever was most masculine.

Though there was one major exception: Jesus Christ. "There's a whole world of female Jesus," says Laqueur. "Christ has an open body. Christ bleeds. There are paintings of Jesus bleeding from his breast and saints are drinking it. This motif goes throughout the medieval era." The most common version of this scene is Catherine of Siena drinking blood from the wound in Christ's chest. In one of her letters she urged, "I, Catherine, servant of the servants of Jesus, write to you in His Precious Blood, wishing only that you feed yourself with God's love and nourish yourself with it as at a mother's breast. Nobody in fact can live without this milk!" Finally we have an answer to the trendy "WWJD" bracelets of the 90s: Breastfeed.