A supporter of LGBT rights holds up an "equality flag" on Capitol Hill in Washington on July 26, 2017. (AP Photo/Jacquelyn Martin)

Last week, the New York Times broke the news that the Department of Health and Human Services has proposed narrowing the definition of sex “on a biological basis that is clear, grounded in science, objective and administrable.” In this framework, sex would be “either male or female, unchangeable, and determined by the genitals that a person is born with.” Any ambiguity would be resolved with genetic testing. As the Times noted, this move would essentially classify transgender and intersex people out of existence.

Rebuttals from trans and intersex people and their allies were immediate. Sex, they argued, isn’t a binary. Scientists agree that there are a wide range of chromosomal types beyond XX and XY — intersex traits of all kinds — and a diverse mixture of environmental and inborn factors shape sex development across a spectrum, not to mention a diversity of gender identities. And biologists and medical and mental health professionals leaped to the defense of the trans community, circulating open letters wielding their expertise to fight back against HHS’s nonsensical definition of sex.

These critiques are correct. But they also fundamentally misunderstand that this redefinition of sex has little to do with biology. This isn’t a scientific debate in which “bad science” can be fought with “good science.” It is about power, and it reflects a long history of hiding violent and exclusionary policy behind claims about the natural order of things.

Since at least the 18th century, Western nations have looked to the natural world to justify social hierarchies. For example, when anatomists began to look for skeletal sex differences in the late 1700s, they determined that women’s cranial capacity was smaller than men’s, while their pelvises were larger. At a time when women were demanding their rights to participate in the public life of new democracies, their opponents turned to these findings to argue that women could only contribute to society as mothers, not as intellectuals or voters.

Supposed physical evidence about sex and race continued to prop up white male authority through the 19th century and into the 20th. In the 19th century, as the question of slavery loomed large in American politics, proslavery writers used assertions about the natural world to justify the cruel institution in part by claiming that African women felt less pain in childbirth because of anatomical differences. This, they claimed, made them perfect reproducers of a captive labor force.

By the turn of the 20th century, scientific reasoning about the supposedly fundamentally different bodies of African Americans — evident in the purportedly masculinity of black women’s bodies — helped to support the imposition of racial segregation.

Ideas from sex science also shaped military and immigration policy. During World War I, men whose bodies medical examiners deemed too feminine — based on narrow shoulders, lack of body hair, excessive breast development or a short stature — were excluded from recruitment. In the 1920s, screeners at Ellis Island turned away people with genitals they determined to be ambiguous. Sexologists had asserted that such people might lead to evolutionary degeneration in the American population, become an economic burden on the state and engage in criminal behavior.

But in each of these cases, what determined a person’s sex varied: skeletal structure determined sex when brain capacity mattered, reproduction when ensuring the future of slavery, body type when preparing for war and genitals when in need of a quick visual determination. In fact, over the past 200 years, scientists have variously defined sex by genitals, gonads, metabolism, reproductive capacity, secondary sex characteristics, hormones and chromosomes — so much for that “clear, objective, and administrable” definition of sex.

It turns out that consensus about what sex is and how to define it has been difficult to find. Why? Because these are decisions about power — who should have it and who shouldn’t — not about science.

In fact the natural world contains more exceptions than rules, and scientists have developed differing methods for making sense of that diversity. That process is particularly clear in their study of binary-defying animals around the turn of the 20th century. Sometimes, scientists crammed every possible physical variation into the categories of “male” and “female” for the sake of preserving a binary. So when anatomist Morrison Watson encountered hyenas that could bear young but had what scientists eventually deemed “pseudo-penises,” he determined them to be normal females on the basis of their ovaries, even though he freely admitted that their bodies looked completely male to the naked eye.

On other occasions, sex was a malleable spectrum. Frank Lillie, whose work shaped the field of sexual endocrinology, found that hormonal conditions in utero influenced the development of sex characteristics. In his observations of cattle, he saw that “female” embryos could develop “male” characteristics in the presence of high levels of testosterone — sex was flexible, and an individual could be moved along a spectrum. This research would ultimately lead to the realization that human bodies, too, could be changed by hormones, expanding the possibilities of medical transition.

Sometimes, a non-binary sex system was even held up as a sign of evolutionary progress. Entomologist E.R. Leland argued ants’ three-sex system of female queens, neuter workers and male drones was the result of a complex division of labor that had led to the development of new, advanced physical forms.

This research went on at the same time that the state was trying to use narrow definitions of sex to prop up its preferred hierarchies. This exposed the reality: Officials cared less about scientific understandings of sex than sociopolitical goals: maintenance of a racial hierarchy, a strong military, a sexually “normal” immigrant population.

The federal government’s present search for binary definition steamrolls the complex understanding of sex that scientists have long possessed but is not interested in the science itself. Rather it wants to invoke the idea of “nature” and the cultural authority of science to justify who it includes and who it excludes from its protections.

HHS’s proposal is a continuation of these earlier, odious attempts to use “nature” to determine social policy. Science is a smokescreen for the current administration’s utter contempt for trans and intersex people, and its investment in maintaining stark differences between men and women.

What’s more, even if sex were biologically binary — and it’s not — we as a society have the capacity to make choices about how we want to treat people.

What sex “really” is, if it really is anything, doesn’t matter. The science is not the problem. The problem is that the Trump administration wants to solidify categories of sex to support whatever nightmarish policies they come up with next. Trans and intersex people deserve rights and recognition no matter how science defines sex.