In the summer of 1881, Frenchman Gustave Le Bon entered the forbidding Tatras Mountains of southern Poland. A bearded man of 40, Le Bon was a Parisian polymath with an appetite for science, anthropology, and psychology. His mission in Poland was to locate and study the society of Podhaleans living in the Tatras. Using the portable cephalometer he invented years prior, Le Bon hoped to record the skull measurements of these curly blonde-haired, blue-eyed mountain people. Convinced of the relationship between race and intellect, Le Bon suspected that only a superior breed could thrive in the inhospitable Tatras — a race that must have evolved beyond their Polish peasant neighbors. How else could they have built a society on terrain so dangerous that even Russian generals avoided sending troops through the peaks?

With his contraption of steel rulers and pressurized screws, Le Bon measured the cranial dimensions of 50 Podhalean men. According to his calculations, their heads were larger than both Polish peasants and Jews. The only population Le Bon determined had more brain mass than the Podhaleans were "elite Parisians," among which Le Bon happened to count himself.

Today craniometry is considered pseudoscience. In 19th-century France, however, the measurement of skulls was seen as "so meticulous and apparently irrefutable," that it "won high esteem as the jewel of 19th century science," explains Stephen Jay Gould in his 1980 essay "Women's Brains." As a result, Le Bon earned a reputation as the "father of modern social science." Gould describes Le Bon as a disciple of Paul Broca, the "unquestioned leader" of craniometry, and writes that Le Bon differentiated himself as the "chief misogynist" of Broca's school. While many craniometrists strived to prove the inferiority of non-white races, Le Bon took pride in using his work to denigrate women and dismiss the burgeoning movement for gender-equal education in France.

"There are a large number of women whose brains are closer in size to those of gorillas than to the most developed male brains," he wrote in a fiery 1879 essay against sending ladies to school. "This inferiority is so obvious that no one can contest it for a moment. … A desire to give them the same education, and to pose the same goals for them, is a dangerous chimera." His remarks explain why he didn't bother to use his cephalometer on a single Podhalean female.

Le Bon's assertions were based on measurements of ancient skulls that Paul Broca excavated from L'Homme Mort cave in 1873. Of the seven male skulls and six female skulls in the cave, the average cranial capacity difference was 99.5 cubic centimeters. Because the modern-day size difference between male and female skulls is larger (129.5 - 220.7 cubic centimeters, to be exact), Le Bon concluded that males had evolved to become more intelligent than females, much as, in his mind, the Podhaleans were evolutionarily more fit than their Polish counterparts.

Children photographed by Le Bon for his study on the society of Podhaleans living in the Tatras | (Courtesy Narratively)

His leap from data to interpretation seemed justified by 19th-century standards. Charles Darwin himself believed that evolution revealed female deficiencies. In The Descent of Man in 1871, Darwin claimed that "the chief distinction in the intellectual powers of the two sexes is shewn by man attaining to a higher eminence, in whatever he takes up, than woman can attain. … Thus man has ultimately become superior to woman." If women could achieve more than men, why hadn't they? Le Bon was merely drawing on facts, with a dash of common sense.

Naturally, contemporary feminists who are familiar with Le Bon loathe his work. His name still crops up in the occasional text, including Andi Zeisler's 2016 We Were Feminists Once, a radical feminist critique of media and pop culture. Zeisler, the co-founder of Bitch Media, points to his gorilla brain comment as a signature example of gender essentialism, or "the belief in binary, fixed differences between men and women that account for 'natural' behavior and characteristics."

Gender essentialism, also known as gender fatalism, insists that men and women come pre-programmed with a set of sex-based qualities. Coincidentally, or maybe not, these qualities usually align with our most prominent cultural narratives about men and women. Prime examples include the common stereotypes that men are competitive, while women are collaborative; that men are physical, while women are emotional; and that men are systems thinkers, while women care about human perspectives.

Illustration of a portable cephalometer invented by Le Bon | (Courtesy Narratively)

Zeisler suggests that his gender essentialist claims still influence education policy, to women's detriment. And sure enough, Le Bon's essentialist approach to gender and the brain continues to thrive. Rather than skull dimensions, in the 21st century it's brain scans and neuro-imaging that have roiled a national conflict. On one side of the debate are gender-based learning advocates pointing to research they call indisputable — brain scans so clear on male/female differences that the only reason for protest is political correctness. Opposing them is a group of academic scientists and women's rights advocates, desperately raising their hands to publicize the harm caused by gender-segregated classrooms. By collaborating with the ACLU, these researchers and lawyers hope to stem the tide of neuro-sexism, the term they've coined to describe the coopting of brain science as a vehicle for gender-based treatment.

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