How then, in the span of less than a century, did the unnatural state of hairlessness become the standard for American women?

The campaign against body hair on women originates in Darwin’s 1871 book Descent of Man, explains Herzig. Men of science obsessed over racial differences in hair type and growth (among other aspects of physical appearance), and as the press popularized these findings, the broader American public latched on. Darwin’s evolutionary theory transformed body hair into a question of competitive selection—so much so that hairiness was deeply pathologized. “Rooted in traditions of comparative racial anatomy, evolutionary thought solidified hair’s associations with ‘primitive’ ancestry and an atavistic return to earlier, ‘less developed’ forms,” Herzig writes. Post-Descent, hairiness became an issue of fitness.

An important distinction in this evolutionary framework was that men were supposed to be hairy, and women were not. Scientists surmised that a clear distinction between the masculine and the feminine indicated “higher anthropological development” in a race. So, hairiness in women became indicative of deviance, and researchers set out to prove it. Herzig tells the story of an 1893 study of 271 cases of insanity in white women, which found that insane women had excessive facial hair more frequently than the sane. Their hairs were also “thicker and stiffer,” more closely resembling those of the “inferior races.” Havelock Ellis, the scholar of human sexuality, claimed that this type of hair growth in women was “linked to criminal violence, strong sexual instincts … [and] exceptional ‘animal vigor.’”

By the early 1900s, unwanted hair was a significant source of discomfort for American women. They desired smooth, sanitized, white skin. They wanted to be feminine. “In a remarkably short time, body hair became disgusting to middle-class American women, its removal a way to separate oneself from cruder people, lower class and immigrant,” writes Herzig.

As hemlines rose, threatening to reveal hairy limbs, women took extreme measures to remove hair.

In the 1920s and ’30s, women used pumice stones or sandpaper to depilate, which caused irritation and scabbing. Some tried modified shoemaker’s waxes. Thousands were killed or permanently disabled by Koremlu, a cream made from the rat poison thallium acetate. It was successful in eliminating hair, and also in causing muscular atrophy, blindness, limb damage, and death. Around the same time, X-ray hair removal emerged as another treatment option. Women would sit for three or four minutes in front of the invisible rays of a boxed X-ray machine, and the radiation would do its work. So great was the appeal of each hair withering away in its sheath that for nearly two decades, women underwent dangerous radiation that led to scarring, ulceration, and cancer.