Defining 'Sex' Isn't as Clear as the Trump Administration Claims

Science shows that a binary model for sex doesn't hold up to human variation.
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People gather at a rally for LGBTQ rights at Washington Square Park on October 21st, 2018, in New York City. Based on a leaked memo, the New York Times had reported that morning that the Trump administration is considering redefining gender as a "biological, immutable condition determined by genitalia at birth," which activists say would subject transgender and gender non-conforming people to discrimination, harassment, and violence.

People gather at a rally for LGBTQ rights at Washington Square Park on October 21st, 2018, in New York City. Based on a leaked memo, the New York Times had reported that morning that the Trump administration is considering redefining gender as a "biological, immutable condition determined by genitalia at birth," which activists say would subject transgender and gender non-conforming people to discrimination, harassment, and violence.

The Trump administration is moving to repeal protections for transgender people by legally defining gender as immutable and based on genitalia, the New York Times reported on October 21st. The Department of Health and Human Services (HHS) is seeking to strictly define "sex" under Title IX, arguing that it was never meant to protect people based on gender identity.

The memo with the proposed guidelines states that "sex means a person's status as male or female based on immutable biological traits identifiable by or before birth," and that "the sex listed on a person's birth certificate, as originally issued, shall constitute definitive proof of a person's sex unless rebutted by reliable genetic evidence." The department calls this definition "clear, grounded in science, objective and administrable." But not only does this policy exclude trans people from governmental and educational protections, the research shows that the way HHS is trying to define "sex" isn't as clear as the department claims. The policy would flatten sex and gender into the same thing. But not only is gender a spectrum, human sex is too.

In popular culture, there's wide agreement that penises come in different shapes and sizes, that testicles hang in different ways with more or less skin, that labia minora can be large enough to peek out of a vulva or small enough to stay in, and that breasts develop and hang in different patterns. Some men can grow thick beards and some can't, while some women have noticeable facial hair and others don't. These variations in human phenotypes (the physical expressions of genetic instructions) don't typically trouble our constructs of male and female; there's enough wiggle room in both for a whole host of different traits. But ambiguous genitalia that don't conform to models, especially in infants, can upset those categories. That's because they're drawn around two simplistic models of two very complicated traits: chromosomal sex and external genitalia.

In freshman biology, you probably learned about sex and chromosomes: Sex is determined at fertilization by the 23rd chromosomal pair. XX is female and XY is male—except for when it's not. That's the CliffsNotes version. The World Health Organization actually says "a strict belief in absolute sexual dimorphism is incorrect."

Genetic sex refers to the make-up of that 23rd pair. An ovum contains an X chromosome, inherited from the mother. The sperm that connects with it will give it either a Y chromosome or another X. Many men are called 46XY (46 chromosomes in 23 pairs, with XY at the end); most women are known as 46XX. But sometimes, a person's chromosomes aren't XX or XY. Humans also present as X, XXX, and XXY, among other combinations.

Those chromosomes determine how a fetus develops, but they don't kick in until about the seventh week of gestation. Before then, we all pretty much look the same: two primitive gonad organs accompanied by two duct systems, waiting for activation. If there's no Y chromosome on the 23rd pair, the gonads typically develop as ovaries; if there is a Y chromosome, it produces a protein that tells the gonads to turn into testes. One set of ducts grows and the other degenerates. Even then, fetuses typically look the same until about 20 weeks, when external genitalia begin to develop.

This is a wildly complex, incredibly fast process: In a matter of weeks, cells divide and multiply and activate, working on the instructions encoded within their genes, changing an embryo into a human infant. During this construction, mutations can, and do, happen. Sometimes they make a fetus incompatible with life, which often triggers a spontaneous abortion, or a miscarriage. (Ten to 20 percent of recognized pregnancies end in spontaneous abortion, and even more happen before a woman realizes she was ever pregnant.) Sometimes, they just result in minor differences in how a person looks. Sometimes, there aren't external differences.

This matters because we don't typically look at an infant's chromosomes to determine their sex—we just look at their genitals. Not all intersex people (the term for anyone who doesn't fit neatly into "male" or "female") have ambiguous genitalia at birth. Many of these chromosomal conditions don't even come with abnormal genitals: Some XY individuals with androgen insensitivity develop typical female genitalia and characteristics; some XX babies with congenital adrenal hyperplasia look like babies we'd easily call male. Some intersex people don't develop atypically until puberty, if at all. And other intersex people, especially older ones, don't know how their genitals looked at birth because they were given cosmetic surgery as children to appear more "normal," a practice intersex activists and experts campaign against as unnecessary and harmful.

All in all, there are five interconnected factors that indicate an individual's sex: gonads, hormones, internal reproductive organs, chromosomes, and external genitalia. These typically align with one another and with a person's secondary sex characteristics (hair growth, voice pitch, fat distribution, and all the other little signs we think of as male or female). But often, they don't, in ways that sometimes aren't discovered until a person tries to have children or has an unrelated health problem. And the percentage of the population this affects is not insignificant: Maybe as many as 2 percent of live births have intersex traits—close to how many people have the blood type B negative.

The Trump administration's attempt to legally erase the existence of transgender people is based on a binaristic understanding of sex that doesn't reflect reality—and a glance at the science quickly reveals that our models of sex and gender identity are socially constructed. Most of all, it assumes that sex, gender, and genitals are only diverse in transgender people. A person with XY chromosomes and internal testes who was assigned female at birth and considers herself a cisgender woman is unintelligible to HHS under these guidelines. Meanwhile, transgender people are erased entirely.

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