Why Sex Is Mostly Binary but Gender Is a Spectrum
Anyone who doubts that genes can specify identity might well have arrived from another planet and failed to notice that the humans come in two fundamental variants: male and female. Cultural critics, queer theorists, fashion photographers, and Lady Gaga have reminded us— accurately—that these categories are not as fundamental as they might seem, and that unsettling ambiguities frequently lurk in their borderlands. But it is hard to dispute three essential facts: that males and females are anatomically and physiologically different; that these anatomical and physiological differences are specified by genes; and that these differences, interposed against cultural and social constructions of the self, have a potent influence on specifying our identities as individuals.
That genes have anything to do with the determination of sex, gender, and gender identity is a relatively new idea in our history. The distinction between the three words is relevant to this discussion. By sex, I mean the anatomic and physiological aspects of male versus female bodies. By gender, I am referring to a more complex idea: the psychic, social, and cultural roles that an individual assumes. By gender identity, I mean an individual’s sense of self (as female versus male, as neither, or as something in between).
For millennia, the basis of the anatomical dissimilarities between men and women—the “anatomical dimorphism” of sex—was poorly understood. At the beginning of the third century, Galen, the most influential anatomist in the ancient world, performed elaborate dissections to try to prove that male and female reproductive organs were analogs of each other, with the male organs turned inside out and the female’s turned outside in. The ovaries, Galen argued, were just internalized testicles retained inside the female body because females lacked some “vital heat” that could extrude the organs. “Turn outward the woman’s [organs] and double the man’s, and you will find the same,” he wrote. Galen’s students and followers stretched this analogy, quite literally, to its absurd point, reasoning that the uterus was the scrotum ballooning inward, and that the fallopian tubes were the seminal vesicles blown up and expanded. The theory was memorialized in a medieval verse, an anatomical mnemonic for medical students:
That, tho’ they of different sex may be,
Yet, on the whole, they’re the same as we:
For those that have the strictest searchers been,
Find women are but men turn’d outside in.
But what force was responsible for turning men “inside out,” or women “outside in,” like socks? Centuries before Galen, the Greek philosopher Anaxagoras, writing around the fifth century B.C., claimed that gender, like New York real estate, was determined entirely by location. Like Pythagoras, Anaxagoras believed that the essence of heredity was carried by male sperm, while the female only “shaped” male semen in the womb to produce the fetus. The inheritance of gender also followed this pattern. Semen produced in the right testicle gave rise to male children, while semen produced in the left testicle gave rise to females. The specification of gender continued in the womb, extending the left-right spatial code sparked off during ejaculation. A male fetus was deposited, with exquisite specificity, in the right horn of the
