The publishing of academic papers denying biological reality isn't slowing down; in fact, it's much worse.
This new one, titled Sex-Associated Variables: A Framework for Neurotoxicology, was just published in Neurotoxicology, a very serious academic journal.
The abstract says, "The phrase 'sex differences'" creates a, quote, "distinct binary," and that "this binary is reductive at best" because, according to them, "sex is a spectrum containing a mosaic of factors," "an amalgamation of contributing factors that are grouped together," and "a conglomeration of variables."
This is the same tired claim we've seen again and again, that males and females are not real and discrete biological categories but rather they exist on a spectrum of maleness and femaleness. The categories are continuous, or a mosaic, or a complicated collection of chromosomes, hormones, anatomy, behaviors, and other traits.
The problem with this argument is actually very simple. It's totally self-refuting and I'll explain why. You see, the authors want to break sex down into what they call Sex-Associated Variables or SAVs. These include morphological variables like breasts and facial hair and genitalia, genetic variables like chromosomes and the SRY gene, and then endocrine variables like testosterone and estrogen.
Now, there's nothing wrong with studying those variables, but the fact that these "sex-associated" variables aren't binary doesn't mean that sex itself isn't binary. It just means the two sexes differ in a lot of ways, and that many of those differences vary continuously, or they overlap. Everybody already knows this. Nobody thinks that sex differences in height, for instance, are binary, with all men being one height and all women being another, shorter height. We all understand that sex differences in height refer to group averages, and this is true for most sex differences.
So here's where the new paper totally collapses under its own logic. The authors spend the entire paper discussing what they call "sex-associated traits," so traits that are associated with being male or being female. They talk about male and female hormonal profiles, male and female sex chromosomes, male and female genital anatomy, and even sex differences in various non-human animal species.
But how do they know, how does anybody know, which traits are associated with males and which traits are associated with females? I want you to really think about that. You can't say that XY chromosomes are associated with being male unless you already know what a male is independently of XY chromosomes. Similarly, you can't say that breast development is associated with females unless you already know what a female is independently of having breasts. And you can't say that higher testosterone is associated with being male in humans unless the category male has already been defined independently of hormone levels.
And what is it that all these "sex-associated traits" are associated with? The answer is having the biological function to produce either sperm or ova. That's it.
This becomes especially obvious when the authors bring up male and female zebrafish in the paper because zebrafish don't have sex chromosomes like humans do, yet nobody is confused about whether zebrafish have males and females and which individuals are which. But why is that? Because male and female are not defined by sex chromosomes. They're not defined by SRY genes or hormone levels. They are defined by the type of gamete an organism has the biological function to produce. This is true across all species that reproduce by fusing an egg and sperm, including species with radically different sex determination systems, endocrine systems, and morphology.
The upstream mechanisms of sex determination vary widely in nature, and the downstream consequences of sex are also very diverse. But what makes an individual male or female does not vary. It's all about gametes.
The paper also uses a figure with a color scheme that's a little suspicious, to say the least, and makes me think that there might be some hidden agenda behind their arguments Maybe it's just a coincidence, but given that the paper repeatedly frames the sex binary as inadequate for transgender, non-binary, or gender-diverse people, individuals whose sex is in no way ambiguous, mind you, it certainly appears like the science is being made to serve a certain political narrative.
And that's, I think, where the real problem actually is. The authors are taking something true and important, the idea that doctors and researchers should pay attention to individual differences, and using it to smuggle in the false notion that males and females are merely social constructs arbitrarily overlaid on continuous variation.
But medicine already understands and accounts for individual variation. A doctor can know a patient's sex while also knowing that hormone levels can vary, that DSDs exist, and that not all men and women respond the same to drugs or toxicants.
The binary nature of sex does not erase or ignore any of this variation; it organizes it. And unfortunately, because this paper is published in a relatively high-impact journal, it will probably be cited over and over again by activists, advocacy groups, journalists, and even lawyers as evidence that science says sex is a spectrum; it's not.
For a deeper breakdown of all the ways that activists and activist academics try to distort the basic biological reality of the sexes, read my paper, Why There Are Exactly Two Sexes, in the journal Archives of Sexual Behavior. It walks through the common arguments that rely on chromosomes, DSDs, spectrum models, polythetic models, and even multilevel models and explains why every attempt to get around gametes ends up relying on them anyway.
Research purporting to demonstrate that trans-identifying individuals’ brains resemble those of the opposite sex often ignores a major confo
By: Colin Wright, Samuel Stagg, Christina Buttons
Published: Mar 14, 2025
Earlier this week, City Journal published the tragic story of Yarden Silveira, a young detransitioner—someone who pursues hormonal and/or surgical “sex change” procedures but then seeks to reverse course—whose life ended abruptly after suffering severe complications from a gender-related genital surgery. What led Yarden to adopt a transgender identity in the first place? In 2014, after encountering the growing wave of pro-trans narratives in popular culture, Yarden told his family that he believed he had a “female brain.” Though initially uncertain, his mother was ultimately convinced by scientific papers that suggested that her son could have a female brain trapped in a male body, and that this mismatch caused him unimaginable distress.
“A trans woman (such as myself) was born with a male body, but she has always had her female brain. Literally born with a female brain,” Yarden wrote in 2016.
This belief was widespread back then—and it still is. On January 31, Wisconsin Public Radio featured an interview with a mother, Carri, concerned about President Trump’s new executive order banning federally funded medical and surgical “sex change” procedures for minors. Carri spoke about her daughter, who identified as transgender at 15 and was allowed to medically transition. She said, “Those hormones really helped match his brain with his body which, to me, that’s just the basic level of care we can provide individuals that identify as trans.”
The power of this narrative in persuading people to pursue, or to allow their children to pursue, irreversible medical procedures cannot be overstated. But the notion that males can have “female brains,” and vice versa, rests on a flawed interpretation of “brain sex” studies that in no way demonstrate or even suggest a definitive biological basis for “gender identity.” Little effort has been made to correct this misleading assertion.
The theory is advanced for relatively straightforward reasons. Civil rights lawyers, activists, and researchers contend that people who identify as transgender possess a “brain sex” misaligned with their physical body, thereby establishing a biological basis for “gender identity” akin to immutable traits like race. This framing carries significant legal weight, as U.S. civil rights law offers strong protections for characteristics considered “innate” or rooted in biology.
In courtrooms, prominent gender clinicians routinely invoke “brain sex” literature to bolster the perceived immutability and innateness of “gender identity.” For example, Daniel Shumer, a pediatric endocrinologist and clinical director of the Child and Adolescent Gender Clinic at Mott Children’s Hospital at Michigan Medicine, provided expert testimony in a case challenging Texas’s prohibition of “gender-affirming care” for minors. He linked “gender identity” to “brain structures,” arguing:
Scientific research and medical literature across disciplines demonstrates that gender identity, like other components of sex, has a strong biological foundation. For example, there are numerous studies detailing the similarities in the brain structures of transgender and non-transgender people with the same gender identity.
Such statements have become standard in legal battles over “gender-affirming care” and other trans-related policies. In Talbott v. Trump, a legal challenge to the president’s executive order barring transgender individuals from military service, Nicolas Talbott—a transgender-identifying female and activist—joined six active-duty service members and two prospective enlistees in arguing that “[s]trong research supports the conclusion that gender identity has a biological basis” and that “transgender women and non-transgender women have similar brain structures, specifically in the volume of the bed nucleus of the stria terminalis.”
Outside the courtroom, the idea of a brain-body mismatch has permeated popular culture, resonating with the “born this way” narrative embraced by many in the LGBT community. Mainstream television and other media have reinforced the concept. For instance, in a 2009 episode of Law & Order: Special Victims Unit, psychiatrist George Huang, played by B.D. Wong, explained that a trans-identified boy had a “female brain”: “For some children, something happens in utero where the brain develops as one gender and the body the other.” Children’s books have reinforced this idea, with the trans-identified protagonist in I Am Jazz declaring, “I have a girl brain but a boy body. This is called transgender. I was born this way!”
There is reason to believe the “brain sex” narrative has influenced many young people’s decisions to pursue medical transition. In a forthcoming survey conducted by coauthor Buttons, 49.2 percent of detransitioner respondents recalled health-care providers framing the respondents’ transgender identity as a brain condition, using phrases like “male brain in a female body,” or vice versa. In total, 85.7 percent of those surveyed said that their providers characterized transgender identity as an inherent, biological trait that required medical intervention.
To bolster these claims, providers often cite a growing body of scientific literature that purportedly validates the brain-body mismatch hypothesis. These studies claim that the neuroanatomy of people identifying as transgender more closely resembles the brain structures typical of the sex with which they identify, relative to non-transgender-identifying controls. Media amplified these findings, often presenting them as definitive proof that trans-identifying people “are who they say they are.” Headlines such as “Science Proves Transgender People Aren’t Making It Up” and “Transgender people are born that way, a new study has found” further entrench the narrative.
Proponents of these studies, however, rarely possess the expertise and background knowledge needed to examine their methods and conclusions critically. And the culturally charged atmosphere surrounding transgender issues means that facts often take a backseat to politically—and legally—expedient narratives.
The central flaw in current research purporting to validate the cross-sex brain hypothesis is an inconsistent—or complete lack of—control for individuals’ sexual orientation. Why does this matter? Because most people who identify as transgender are not exclusively heterosexual, and same-sex attraction has been linked to neuroanatomical differences that reflect a cross-sex shift—or, more broadly, to a reduction in typical sexual dimorphism (i.e., to having more androgynous brain structures). This raises serious methodological concerns about the extent to which sexual orientation might confound or interact with the neurobiological markers that “brain sex” studies routinely attribute to gender dysphoria. It also raises major ethical concerns about the use of “gender-affirming care” as a form of gay conversion therapy or as a maladaptive coping strategy for gay men.
If one properly controls for sexual orientation, the reported neuroanatomical shifts in transgender brain-scan studies diminish greatly or vanish entirely. To illustrate that point, consider three influential studies examining regional gray matter differences between transgender-identifying individuals and controls. These examples, considered together, illustrate a pervasive problem in the “brain sex” literature.
The first study, by Lajos Simon et al. and titled “Regional Grey Matter Structure Differences between Transsexuals and Healthy Controls—A Voxel Based Morphometry Study,” reported that trans-identifying individuals exhibit brain structures more closely resembling those of the opposite sex, relative to controls. This study is frequently cited as evidence supporting the brain-sex hypothesis. However, a different study by Eileen Luders et al. titled “Regional gray matter variation in male-to-female transsexualism,” which used similar neuroimaging techniques, found no significant differences overall in gray-matter volume between male-to-female (MtF) trans-identifying individuals and male controls. In one small brain region, the putamen, the MtFs did exhibit a cross-sex shift, relative to their dataset—i.e., putamen volumes in MtFs were larger and more similar to female controls—but this result is anomalous and incongruent with the findings of large-scale studies and meta-analyses demonstrating that males, not females, have larger putamen gray-matter volumes, on average.
A third study, by Ivanka Savic and Stefan Arver titled “Sex Dimorphism of the Brain in Male-to-Female Transsexuals,” comprehensively analyzed structural brain differences using MRI. While the authors observed some structural differences in the brains of trans-identifying men compared with those of non-trans-identifying male controls, these differences did not align neatly with a feminization pattern. Instead, the variations were distinct from typical male or female brain structures, suggesting a unique neuroanatomical profile rather than a simple cross-sex shift. Importantly, Savic and Arver controlled for participants’ sexual orientation and found that, when they did so, the brain differences attributed to gender dysphoria were much less pronounced.
A clear pattern emerges when comparing these and similar studies: the magnitude of the cross-sex shift reported in trans-identified individuals’ brains correlates with the proportion of homosexuals in the sample. For example, in Simon et al.’s study, all transgender participants were homosexual, potentially amplifying participants’ sex-atypical neuroanatomical features. In contrast, Luders et al.’s cohort had a much lower proportion of homosexual participants, coinciding with null findings overall regarding brain feminization. Savic and Arver’s rigorous control for sexual orientation further demonstrates that some neuroanatomical differences previously attributed to gender dysphoria likely reflect—or are confounded by—sexual orientation-related brain variations.
Popular “transgender brain” studies, in short, often fail to control for sexuality, undermining the claim that people with transgender identities have brains that more closely resemble those of the opposite sex.
What would it mean if the “transgender brain” hypothesis were true, and properly controlled studies did document a statistically significant cross-sex shift in the brains of people who identify as transgender? It would not logically follow that a brain scan can capture a person’s “gender identity”—just as brain scans cannot ascertain a person’s sexuality. Differences in group averages do not mean that every individual within a group shares those characteristics. Populations contain variance; for instance, some straight men exhibit brain structures that skew feminine, while some gay men exhibit brain structures that skew masculine. Brain scans therefore cannot verify whether a person is homosexual; nor could they verify whether a person “is transgender.” Brains, like most physical traits apart from primary sex organs, are not discretely sexed; they simply exhibit average differences between the sexes.
Even if there were compelling evidence for “brain sex,” gender clinicians, though often expressing strong confidence in the hypothesis, would be the last to advocate for the use of objective brain scans to validate their claims. Their hesitancy has roots in the history of sexuality research. When scientists proposed the existence of a “gay brain,” many gay rights advocates strongly objected, citing its potential for eugenic abuse (imagine, for example, a drug company developing a fetal “treatment” to “cure” homosexuality based on such findings). Despite progressives’ deep pessimism about science’s potential for abuse, however, many activists still peddle the “brain sex” narrative.
Notably, even though homosexuality is associated with a cross-sex shift in certain brain structures, activists avoid claiming that gays and lesbians exhibit a brain-body mismatch. This avoidance highlights a striking inconsistency in the application of the “brain sex” narrative. For decades, research has shown that homosexuals exhibit subtle neuroanatomical differences that trend toward patterns typical of the opposite sex. Yet, proponents of LGBT rights have rejected the notion that these differences imply a pathological misalignment requiring medical correction.
The persistence of the “brain sex” narrative has real and sometimes tragic consequences. For individuals like Yarden Silveira, it contributed to life-altering—and ultimately life-ending—medical decisions based on a flawed understanding of the science. The notion that transgender identity is rooted in immutable brain structure has led countless young people to undergo unnecessary and often harmful medical treatments, frequently without fully informed consent or consideration of alternative approaches. Challenging that notion isn’t just an academic exercise—it’s a necessary step toward protecting vulnerable individuals from medical abuse.
Policymakers should mandate rigorous, independent reviews of the scientific claims surrounding transgender identity’s supposedly biological basis. This review should include scrutinizing studies that promote the “transgender brain” hypothesis, and incorporate evidence from desistance and detransition research, which highlight how transgender identities are often transient.
Public-health policies must be grounded in comprehensive and unbiased research. Otherwise, vulnerable young people will continue to face irrevocable and potentially devastating treatments.
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It's funny how there are supposedly no differences between males and females when it comes to sports, and yet there are supposedly MRI-detectable "male brains" and "female brains."
🤔
This ideology is completely incoherent.
It's astonishing how many formerly reputable scientific institutions have embraced abject pseudoscientific gobbledygook.
A Montana court just ruled biological sex laws are unconstitutional — and fake academic science is how the Left made it happen.
By: Colin Wright
Published: Apr 22, 2026
The Montana Supreme Court’s decision last week in Kalarchik v. State should put to rest the Right’s celebratory mantra that “woke is dead.” It isn’t.
In a 5–2 ruling, the court upheld a preliminary injunction blocking enforcement of key parts of Montana’s 2023 law, SB 458, and related agency policies that defined sex in binary, biological terms and limited changes to birth certificates and driver’s licenses.
The ruling does not finally invalidate the law, but it allows Montanans with transgender or “nonbinary” identities to continue changing the sex marker on identity documents while the constitutional challenge proceeds. More importantly, the majority signaled its view that the challenged policies likely violate Montana’s constitution, holding that “transgender discrimination is, by its very nature, sex discrimination” and subjecting the state’s policy to strict scrutiny.
That outcome matters well beyond Montana, because it shows how thoroughly activist ideologies about sex and gender have penetrated elite institutions, including courts in conservative states. Montana’s legislature had attempted to define sex in law using objective biological criteria tied to reproductive function, while excluding “psychological, behavioral, social, chosen, or subjective experience of gender.” The court majority treated the refusal to translate gender identity into official sex classification as a form of unlawful sex discrimination.
Many of these sex-denying policies were not a result of some revolutionary scientific discovery, but from a form of linguistic capture. Existing legal terms were instead reinterpreted and redefined. “Sex,” once understood as a biological classification, was gradually made to include “gender identity,” a subjective feeling. Once an objective biological anchor is gone, policy will go wherever activists want to pull it. Montana tried to reinstate that anchor and failed.
That has been the standard pattern. The cultural campaign against the biological reality of sex began in niche activist blogs, women’s studies departments, and obscure ideological magazines. But it eventually moved into mainstream journalism and then into scientific and scholarly journals, where it acquired the prestige that courts and bureaucracies necessarily treat as authoritative.
In just the last few weeks, many outlets have been promoting this sex pseudoscience. Princeton anthropologist Agustin Fuentes argued in Science Politics that government efforts to define sex as a biological binary incorporate “falsehoods and erroneous assertions.” IFLScience ran a piece insisting there is “no clean definition” of biological sex. A piece from the Trans Advocacy & Complaints Collective declared that “sex does not fit neatly in boxes.” A new BioScience paper reported that teaching students “the diversity of biological sex” increased LGBTQIA+ students’ “sense of belonging.” And an Ecology Letters paper concluded that there is “no current consensus” on biological sex. It’s safe to say that the war on biology hasn’t slowed down. It has, in my estimation, been dramatically accelerating.
The main issue is not that these arguments are simply wrong, but that they create the appearance of scientific doubt around fundamental biological facts. Once enough papers and essays circulate claiming that sex is a spectrum or based on clusters of mutable traits, or something with “no consensus” definition, judges and policymakers can present themselves as merely choosing among competing expert views.
But this is a manufactured controversy, because the basic biological claim that males and females are reproductive classes rooted in anisogamy (sperm vs ova) has not been overturned. Activists have merely expanded the topic from sex to everything associated with sex — hormones, morphology, behavior, developmental pathways, social roles — and then act as though the resulting complexity is proof that sex itself defies categorization.
That sleight of hand was on display in a recent debate at the University of Delaware between Agustin Fuentes and philosopher Tomas Bogardus. Before the debate even began, moderator Joel Pust had to defend the legitimacy of discussing whether biological sex is binary at all, noting that some critics objected to the event’s very occurrence on the grounds that it could cause harm.
Yet, the debate also exposed why the activists have vehemently held a position of “no debate” for so long. Fuentes explicitly conceded that humans have two sexes, male and female, and said that when he speaks of sex as being a “spectrum,” he does not mean three sexes or five sexes. Instead, his strategy is to widen the discourse around sex itself to what he calls “sex biology,” a much broader category encompassing every axis that bodies, behaviors, endocrine systems, morphology, etc., can vary between the sexes. He emphasized overlapping distributions in height, weight, hormones, fat deposition, and other traits, then argued that because these traits are not distributed in perfectly discrete ways, a binary framing is not biologically sound or useful.
Bogardus, by contrast, kept returning to the central question of the debate: what sex is, and how many there are. His (correct) answer was that male and female are functional reproductive classes rooted in producing either sperm or ova, and that variation in correlates of sex does not negate the two (and therefore binary) sex categories themselves.
Of course, it is true that not every sexually dimorphic trait is binary. Of course, males and females overlap in countless characteristics. No biologist thinks every trait in an organism falls into two perfect, non-overlapping bins. That has never been the claim. The claim is that in anisogamous species (those that reproduce by fusing sperm and ova), there are two sexes because there are two reproductive functions based on two gamete types. This is precisely the point I made in my 2025 Archives of Sexual Behavior commentary, “Why There Are Exactly Two Sexes.” I also addressed the routine attempts to dissolve sex into trait clusters, and explained why these activist models actually presuppose the gamete-based model they seek to replace.
The legal implications of activist pseudoscience are very serious because once sex is no longer understood as a reproductive classification but as an aggregate of partly overlapping traits, it becomes infinitely malleable. Courts can then say that because people differ in complicated ways and because some sex-related traits do not line up neatly, the state has no principled basis for keeping sex distinct from identity. This is how law begins to privilege a pseudoscientific account of human beings while portraying those defending the true biological understanding of sex as ideologues.
My own paper was recently the target of a Letter to the Editor in the same journal by the German scholar Dana Mahr. I welcomed the criticism because robust public debate about the facts is healthy. But rather than making a scientific refutation of my paper, Mahr chose to critique it from a “feminist epistemology” perspective, arguing that defining male and female by gametes is simply a choice shaped by historical and cultural norms.
In my published response, I pointed out that while the labels we assign to the reproductive classes “male” and “female” are conventional, the underlying reproductive phenomenon is not. The fact that anisogamous organisms reproduce through the fusion of two gamete types is no more created by language than the molecular structure of water is created by language. The real issue is whether our categories track a mind-independent feature of nature. In the case of biological sex, they do.
Our exchange encapsulates the entire conflict. On one side is the view that biology describes real features of the world. On the other is the claim that concepts literally create the world, and that our definitions should therefore bend toward achieving social and political goals.
Some people still proclaim that woke has peaked, is now trending down, and that the country is finally moving on. There is some truth to that politically, because the backlash against woke is real, and the public is more skeptical and informed than it was five or 10 years ago. The Trump administration has moved to restore biological language in federal policy, and more scholars are now willing to defend basic biological realities in print.
But surveying the daily output of academia, which I do regularly, gives no indication that the activist project is in retreat. It is simply consolidating. If you want to know where the next round of policy battles will come from, do not watch the news or scroll your social media feed. Read the journals.
Some of my colleagues believe, and I agree with them, that we have entered the “lawfare” stage of this conflict. The people who are reachable have now heard the arguments and chosen their side. The fight is no longer mainly about consciousness-raising, but policy implementation.
Which view of sex will be written into state and federal policy? Which view will courts treat as authoritative? Which view will medical boards, licensing agencies, school systems, and bureaucracies be able to cite as settled expertise? Those questions will be answered, in large part, by what appears in the academic literature. Progressives understand this and are playing the long game by saturating academic journals with ideological nonsense.
The Montana decision should be understood in that light and serve as a warning. Even in a red state, after years of public controversy and after legislators tried to write biological reality back into law, the highest court in the state treated that attempt as unconstitutional discrimination.
This is why serious scholars, now more than ever, must start actively engaging with activist pseudoscience in academic journals. Social media posts and think pieces are not nearly enough to combat the Left’s slow manufacturing of expert consensus where it matters most.
Trump is right about the science of sex. That doesn’t mean he’s got the right policies on gender.
By: Carole Hooven
Published: Feb 20, 2025
“It is the policy of the United States to recognize two sexes, male and female.” “‘Female’ means a person belonging, at conception, to the sex that produces the large reproductive cell.”
Those are statements from President Trump’s Jan. 20 executive order titled “Defending Women From Gender Ideology Extremism and Restoring Biological Truth to the Federal Government.” In addition to making various declarations about sex in humans — that it is immutable, binary, and based on whether an individual produces large or small reproductive cells (eggs or sperm) — the order also set out new policies, such as limiting sex markers on federal documents to “the holder’s sex” (either “M” or “F”), removing “nonbinary” marker options like “X” on passports, and forbidding the alteration of birth certificates to reflect gender identity.
For many, these words churned up dread, anger, and fear that they would lose identity-based rights and freedoms. For others, it was a relief — a return to what they saw as biological reality in federal policy.
As a scientist specializing in the evolutionary biology of sex differences — researching and teaching at Harvard for more than two decades, and having written a book on the subject — I’m not surprised by the strong reactions. Trump’s definition of sex is rigid and unforgiving: It’s understandable why many might long for a softer, more inclusive one.
On President Biden’s first day on the job in January 2021, he, like Trump, issued a slew of executive orders. One mandated that federal agencies interpret the word “sex” in federal law to include “gender identity.” Over his presidency, Biden issued multiple policies that advocated for rights to public spaces, activities, and health care to be based on self-identified sex, rather than sex recorded at birth. This meant, for example, that transgender women and girls could compete on female sports teams, be housed with females in the military or prison, and use women’s restrooms. Perhaps these policies were kinder and gentler. As the Globe put it in a 2021 headline, “Biden offers LGBTQ protections, an ideological departure from Trump-era policy.”
Ideally, political beliefs would not bias views of scientific reality. But take a look at how the media covered the Trump administration’s new executive order. The Globe: “Trump executive order misstates facts about sex and gender, scientists say.” Time: “Trump’s ‘Biological Truth’ Executive Order Is Not Based in Biology or Truth.” The Guardian: “Most scientists now reject the idea that sex is strictly binary” and “sex is a hell of a lot more complicated than Trump’s executive order would have you believe.” NBC: “The executive order questions [transgender people’s] existence by saying the government would recognize only two unchangeable sexes: female and male.”
As for Fox News: “Trump is returning sanity to the gender conversation.”
Many journalists — and the experts they consult — seem unable to disentangle their politics from analysis of the relevant science. I’m a Democrat, and I have never voted for a Republican. Yet while I might have worded things in Trump’s executive order a little differently, I agree with the way this administration has defined sex.
There are two and only two sexes. Sex is immutable in humans and other mammals, and it is defined by gamete size. (I’ll discuss some of the technicalities shortly.)
I’d love to live in a world in which children in particular felt comfortable expressing themselves as they saw fit, regardless of whether that expression was sex-typical. To promote such a culture, we adults don’t need to pretend that sex is not a biological reality, claim that sex can be changed, or deny the natural differences between boys and girls, men and women. Instead, we should foster an environment that respects individual expression, while also acknowledging biological reality.
Unfortunately, mainstream coverage has elided basic biological facts and misled the public about what sex actually is.
What’s actually on a spectrum
Some critics of the definition of sex in Trump’s executive order had a somewhat picky objection to the wording, arguing that fertilized eggs don’t “belong to a sex” at conception. Sex is determined at fertilization, when the DNA from each gamete type (sperm and egg) combines. The fetus differentiates into one sex or the other a few weeks later, when either testes or ovaries begin to develop.
But that detail doesn’t undermine the central idea — that sex is defined by gamete size, sperm being the small ones and eggs being the larger ones.
A single fertilized cell contains all of the genes that will determine its fetal fate of becoming male or female. If the Y chromosome is present in an embryo, “undifferentiated” gonads begin developing into testes at about six weeks. If not, ovaries will develop. At that point, sex is not just genetically programmed, it’s developing physically.
A newborn baby doesn’t suddenly take on a sex at birth when its genitals are examined by the doctor. In almost every case, the fetus has been male or female, based on how its gonads have differentiated, for at least seven months.
Another argument made against the definition used in Trump’s order is that if sex depends on gamete production, then people who don’t make gametes, like little boys and girls, postmenopausal women, and those with reproductive problems, would all be sexless!
Well, no. The definition of “female” as “large gamete producer” should be interpreted properly. It doesn’t mean that all females currently produce large gametes. I’m not producing any but I’m still female. The definition doesn’t even imply that females ever produce large gametes. The definition only requires that an individual has traveled some distance down a developmental pathway to create a reproductive system that has the potential (or function) to produce large (rather than small) gametes.
And last, we have the most common argument against the sex binary, which is that “sex is too complex and varied to be binary.” Some version of this argument is made in all the articles I cited above, with the exception of Fox News.
The flaw in the argument is that it conflates traits that are associated with sex with sex itself.
Here’s an example. Under the headline “Trump’s Definitions of ‘Male’ and ‘Female’ Are Nonsense Science With Staggering Ramifications,” Mother Jones published an interview with a scientist with expertise in sex and gender. The journalist begins by asking “a straightforward question: How do scientists define sex?” The scientist replies: “There is no one definition of sex. For scientists, the way you might choose to define it can and should vary based on your research question.”
We learn, correctly, that chromosomes, genitals, hormone levels, and even brains don’t just come in two categories that align with what we traditionally think of as one sex category or the other. The scientist points out, for example, that some people we might think of as male have XYY or XXY sex chromosomes, which aren’t typical of either sex. The scientist also mentions that people with ovaries can have higher androgen levels than are typical of people we “might put in the sex category of female.”
She leaves readers with little doubt about her view of the quality of Trump’s definition of sex: “The scientist in me is in disbelief at how stupid it is. How can you so fully misunderstand basic human biology and then legislate about it?”
Critics often argue that the existence of people who have atypical sex chromosomes and/or genitalia shows that sex is not binary. These kinds of differences are often referred to as “intersex” conditions or “DSDs” (differences of sexual development). Less than 0.02 percent of the population has an intersex condition (not 2 percent, as is often cited) and about 0.3 percent of the population has a DSD. In the DSD Klinefelter syndrome, for example, males have XXY instead of XY sex chromosomes, leading to differences in testicle size, sperm quality, and limb proportions. These people are male because their Y chromosome led to the differentiation of their gonads into testes, meaning they have the potential to (and do) produce sperm. In other, exceedingly rare intersex cases, people have gonadal tissue of both sexes. Having such a condition is not the same as being transgender, which has more to do with feeling intense discomfort with the sexed features of one’s body.
The more we understand about the wide variety of characteristics that can be associated with one sex or the other — like genes, genitalia, hormone levels, muscle mass, or even how individuals feel and act — the better able we will be to meet the medical, psychological, and social needs of those with rare variations. But variation in characteristics that are associated with sex does not constitute evidence for additional sexes. Nor does it mean that sex itself is somehow on a spectrum.
What it instead shows is that sex-associated traits do exist on a spectrum.
Humans and other animals
Any account of sex needs to stretch beyond humans, extending to every female or male organism that has ever existed, beginning one billion to two billion years ago. The real beauty in the gamete-based definition is that it accommodates the immense variation that nature offers.
For example, most flowering plants are both male and female, because they produce sperm and ova. In crocodiles, sex is determined not by chromosomes at conception but instead by the temperature at which the eggs are incubated. Clownfish can change sex, first producing sperm from testes and later developing egg-producing ovaries. In seahorses, the males give birth. In hyenas, females give birth through what looks exactly like a penis. And in humans, males sometimes provide more care to their offspring than females.
The only trait that all male organisms share is the potential to produce sperm. Similarly, the only trait that all females share is the potential to produce eggs.
The gamete-based definition of sex can provide insight into sex differences in our own species. Despite the vast natural variation among individuals, one constant stands out: Sperm producers compete — often fiercely — for access to egg producers, while egg producers invest more in parenting, beginning with the eggs themselves. The divide is especially stark in mammals, in which the mother must provide the time, home, and fuel to grow the offspring during pregnancy, and milk after birth. Fathers need only contribute a single sperm.
Men are unusual among mammals in that they often choose to stick around and invest in their offspring after fertilization. But overall, men benefit more, reproductively speaking, than women do from competing and taking physical risks to attain new mates. This can include intimidating rivals, fighting for social status, or even using violence to get sex. Women tend to benefit more by staying cautious, since they have fewer opportunities to reproduce and must focus more on keeping themselves and their children safe. These kinds of differences help to explain why I avoid running in isolated areas while my husband feels at ease, why men are more likely to die in car accidents, and why women naturally carry more body fat.
Sex is written into law for a reason: There are situations in which it might make sense for boys and men not to have all the same rights as girls and women. For instance, perhaps women should have exclusive access to lactation rooms and women’s sports teams. Perhaps it’s reasonable to consider men’s-only spaces such as military quarters or social clubs. Yet the fact that we are born into one of two sexes doesn’t necessarily mean that our sex should always matter or that official documents must always reflect it. (In the United States, the sex marker on passports wasn’t required until 1977.) But constructive discussion about the implications of sex cannot happen if we can’t agree on basic facts and the language to describe them.
What are our options, as scholars and journalists, if we are concerned about science landing in the “wrong hands” and being “weaponized”? Should we refrain from doing the research that would produce such inconvenient facts, or keep them out of the public eye? Produce journalism that only reports that which appears to support a preferred narrative? Shame those who share facts that the “other side” could to use to advance their own agendas?
All of this is going on, and it’s bad for science, bad for trust in our academic and journalistic institutions, and just bad for democracy. Vulnerable people especially deserve honesty, dignity, and compassion. I hope we can agree that the facts of nature are not what provide the justification for treating people with dignity and respect. We should do that in any case.
You don’t need to have a PhD from Harvard to know the truth here, and you shouldn’t need courage to say it. Whether the policies in Trump’s executive order are justifiable is something reasonable people can disagree about. But as for the scientific facts: The order got those right.
Carole Hooven is an evolutionary biologist, a senior fellow at the American Enterprise Institute, and the author of “T: The Story of Testosterone, the Hormone That Dominates and Divides Us.”
[ Archive: https://archive.today/EKCXu ]
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If the humble rat can figure out how to reproduce, there's no reason to think any humans genuinely believe there's anything other than male and female.
What's going on is just Queer Theory, not some expansion of human biological knowledge. It's the belief that objective reality is "unfair," and we should redefine things to just ignore this and structure society as if reality was as it "should" be.
How do we know this? When you describe objective reality, you're told that's "bigoted" or istaphobic. Same as when you tell Xians that evolution is objectively true and they get offended: "i AiN't ReLaTeD tO nO mOnKeY!1!"
Debunking all five frameworks that claim to refute the sex binary.
By: Colin Wright
Published: Nov 6, 2024
Author’s Note
This essay reproduces in full my Commentary published in Archives of Sexual Behavior as part of its series, “How Many Sexes Are There? How Many Genders Are There?” The commentary systematically debunks all five frameworks that purport to refute the binary nature of sex. Every argument I have ever encountered against the sex binary fits into one or more of these five models—and each collapses under scrutiny.
I explain why biological sex is binary in all anisogamous species, defined strictly by the type of gamete—sperm or ova—that an organism’s reproductive system has the biological function to produce.
I see this commentary, and the broader series it belongs to, as a pivotal moment: a reassertion of empirical clarity in a field long clouded by ideology. The sex binary is storming back, and scientific sanity is being restored to the biology of sex.
If you’re looking for an academic work to cite that rigorously lays out why sex is binary—and why every alternative model either fails or quietly presupposes the gametic definition—this is it.
Why There Are Exactly Two Sexes
Across anisogamous species, the existence of two—and only two—sexes has been a settled matter in modern biology (Lehtonen et al., 2016; Parker et al., 1972). “Male” designates organisms whose biological function is to produce small gametes (sperm), and “female” designates organisms whose biological function is to produce large gametes (ova) (Hilton & Wright, 2023; Minot, 1888; Smith, 1978). This nomenclature reflects two divergent reproductive strategies that recur across a wide range of taxa (Togashi & Cox, 2011). As with the fact of evolution itself, contemporary scientific debates have long moved on from questioning whether the sex binary is a fact to questions about how anisogamy evolved, why it persists, and what its evolutionary consequences are.
In recent years, however, this previously uncontroversial fact has been challenged in popular discourse (Fuentes, 2023; Kralick, 2018; Viloria & Nieto, 2020) and now increasingly in scholarly scientific publications (Ainsworth, 2015; Fuentes, 2025; McLaughlin et al., 2023; Velocci, 2024), seemingly driven by cultural and political debates surrounding the concept of “gender identity” and transgender rights. Popular outlets now routinely publish articles asserting that there are more than two sexes or that sex is a nonbinary “spectrum” conceived as a continuum or as a multivariate cluster of traits. Scholarly articles have amplified this framing by characterizing the sex binary as overly simplistic, outdated, and even oppressive, urging its replacement with broader and putatively more nuanced models (Ainsworth, 2015).
Here I synthesize evolutionary and developmental evidence to demonstrate that sex is binary (i.e., there are only two sexes) in all anisogamous species and that males and females are defined universally by the type of gamete they have the biological function to produce—not by karyotypes, secondary sexual characteristics, or other correlates.
I begin with a concise account of sexual reproduction and the evolution of anisogamy, explaining why two differentiated gamete types evolved from isogamous ancestors and how this functional dimorphism grounds the categories “male” and “female.” I then assess five recurrent arguments used to undermine the binary nature of sex: (1) conflating “mating types” with sexes; (2) treating sex chromosome aneuploidies and karyotype variation as additional sexes; (3) reclassifying differences/disorders of sex development as evidence for a nonbinary “sex spectrum”; (4) recasting sex as a polythetic cluster of traits; and (5) proposing “multilevel” models that attach sex labels not to individual organisms but only to specific traits. Finally, I outline the scientific and societal benefits of definitional clarity, and close by explaining why attempts to decenter gametes are inherently self-defeating because all coherent routes to “male” and “female” remain intelligible only with respect to sperm and ova.
The Evolutionary and Biological Basis of the Sex Binary
What Sex Is and Why It Evolved
Sexual reproduction is the formation of a new organism by the fusion of haploid gametes (syngamy) produced via meiosis (Alberts et al., 2014). By reshuffling genetic variation through recombination and outcrossing, sexual reproduction generates novel genotypes and can reduce the genetic load, which helps explain its persistence despite the costs (Kondrashov, 1988; Otto, 2009).
At the gametic level, sexual reproduction occurs in two broad modes that differ in the size of gametes being fused (Togashi & Cox, 2011). In isogamy, fusion involves gametes of equal size. In anisogamy, fusion involves differently sized gametes (Lehtonen et al., 2016). Anisogamy is thought to have evolved over one billion years ago (Butterfield, 2000) from isogamous ancestors via disruptive selection favoring two distinct gamete types: small, typically motile gametes optimized for quantity and encounter rate (sperm) and large, nutrient-rich gametes optimized for provisioning (ova) (Levitan, 2006; Parker, 2011; Parker et al., 1972). Working in concert, these divergent strategies maximize fertilization success and offspring survival.
The sexes—male and female—refer to these two distinct reproductive strategies in anisogamous species. Males are defined as the sex that produces numerous small gametes (sperm). Females, conversely, are defined as the sex that yields fewer but larger gametes (ova) (Parker, 2011; Williams, 1975). Accordingly, individuals are categorized as male or female based on whether their reproductive system has the biological function to produce sperm or ova, respectively (Bogardus, 2025). Because sperm and ova are the only two gamete classes in anisogamous systems, there are only two sexes. This gametic dimorphism underlies biologists’ reference to sex as a “binary” (Hilton & Wright, 2023).
Common Arguments Against the Binary and Why They Fail
Sexes as Mating Types
Popular and scholarly articles sometimes claim that certain fungi and slime molds have “hundreds” or even “thousands” of sexes (GrrlScientist, 2019; Scharping, 2017). These claims commit a category error by conflating mating types with sexes (Lehtonen et al., 2012). In isogamous taxa, mating types are genetically or molecularly defined compatibility classes that regulate which gametes can fuse; they are not differentiated by gamete size (Hurst & Hamilton, 1992). By contrast, sexes in anisogamous taxa are defined by gametic dimorphism—the production of small gametes (sperm) versus large gametes (ova). Some anisogamous species may also possess mating-type systems layered on top of male and female functions, but isogamous species, by definition, lack sexes.
Claims of hundreds or thousands of sexes thus refer to many mating types in isogamous systems, not to sexes. Where reproduction is anisogamous, the number of sexes remains two—male and female—defined by gamete type (Lehtonen, 2021).
Sexes as Karyotypes
A common line of argumentation used to undermine the binary nature of sex does so by misrepresenting the sex binary as a binary of human karyotypes (XX = female; XY = male) and then citing sex chromosome aneuploidies (e.g., XXY in Klinefelter syndrome; X0 in Turner syndrome) or rare XX males and XY females to claim there must be “more than two sexes” (Ainsworth, 2015; Blackless et al., 2000). How could sex be binary and determined by sex chromosomes, they argue, if there are more viable sex chromosome karyotypes in humans beyond XX and XY?
The fundamental flaw is conflating how sex is determined with how it is defined (Capel, 2017; Griffiths, 2021; Hilton & Wright, 2023). In developmental biology, sex determination refers to the mechanisms that trigger and regulate sexual development. These mechanisms vary widely across taxa (Bachtrog, 2014). Examples include chromosomal (e.g., SRY gene on Y chromosome in mammals), temperature-dependent (e.g., higher temperatures produce males in many reptiles), haplodiploidy (e.g., unfertilized haploid eggs yield males in most Hymenoptera insects), or environmental (e.g., chemical cues in Bonellia viridis).
Yet, regardless of the mechanism by which sex is determined, an individual’s sex—male or female—is universally defined by the type of gamete (sperm or ova) their reproductive system has the biological function to produce (Goymann et al., 2023). Sex chromosome aneuploidies therefore represent variations within the two sexes, not additional sexes.
Sex as a Spectrum
While claims that there are “more than two sexes” are common, the most frequent challenge against the binary nature of sex asserts that sex is a “spectrum” (Ainsworth, 2015; Fuentes, 2025). On this view, “male” and “female” are not distinct biological categories, but theoretical endpoints of a continuous distribution that individuals can only ever statistically approximate. This model entails that individuals can only be described in degrees of maleness and femaleness, rather than strictly male or female. The primary evidence invoked to support the spectrum model is the existence of disorders/differences in sex development (DSDs) (Sax, 2002), including forms of genital or gonadal atypicality, often presented visually along a continuum from “typical female” to “typical male.”
However, the existence of such conditions does not undermine the binary nature of sex, because the sex binary does not entail that every individual can be unambiguously categorized as male or female. Rather, the claim is that in anisogamous organisms there are only two gamete types, sperm and ova, and thus only two sexes. Sexual ambiguity is not a third or intermediate sex because developmental variation does not correspond to producing new gamete types.
Sexes as Polythetic Categories
A polythetic category is one in which members share overlapping characteristics, with no single feature necessary or sufficient for membership. Inclusion is based on “family resemblance”: Each member shares enough traits with others to be recognized as part of the set, even though not all members share the same combination of traits (Needham, 1975; Wittgenstein, 1953).
Proponents of a polythetic sex model draw on this idea to portray sex as multivariate (rather than univariate, as in a simple “spectrum”). On this view, “sex” is an aggregate of traits—chromosomes, gonads, gametes, hormones, neuroanatomy, secondary sex characteristics, and other sexually dimorphic traits—and individuals are assigned degrees of maleness or femaleness according to how their overall profile aligns with what is considered male-typical or female-typical (Dreger, 2000; Fausto-Sterling, 2000).
However, male and female are not polythetic categories. They are reproductive classes defined by a single criterion: The type of gamete (sperm or ova) an organism’s reproductive system has the biological function to produce. All other traits—karyotype, genital morphology, hormone profiles, neurological and somatic dimorphisms—are typically causes, proxies, or consequences of that functional distinction. Treating those correlates as jointly definitional blurs the determinants and downstream effects of sex with sex itself.
Moreover, the polythetic approach is logically self-refuting (Griffiths, 2021). Traits are labeled “male-typical” or “female-typical” because they correlate with males and females already identified independently—ultimately by reference to gametes. In other words, the model presupposes the binary categories rooted in gametes it seeks to replace and then infers those categories back from their correlates. As a descriptive framework for trait variation, a multivariate summary can be useful; as a definition of sex, it is nonsensical.
The Multilevel Sex Model
The multilevel model blends spectrum and polythetic approaches by distributing “sex” across several putative “levels”, commonly including sex chromosomes, internal reproductive anatomy, external genitalia, secondary sexual characteristics, hormone profiles, and behavior, and sometimes extending to “gender identity” (Migeon & Wisniewski, 1998). Rather than classifying organisms as male or female, the model assigns sex labels to traits or levels (e.g., “genetic sex,” “endocrine sex,” “morphological sex,” “behavioral sex,” and so on) (McLaughlin et al., 2023; Sun et al., 2023).
As articulated by McLaughlin et al. (2023), sex is framed as “a constructed category operating at multiple biological levels,” with four focal levels: genetic, endocrine, morphological, and behavioral. This framing conflates the determinants and correlates of sex with sex itself (Bachtrog, 2014; Capel, 2017). Genes and gene networks initiate and regulate sexual differentiation; hormones mediate downstream development and phenotypic dimorphisms; morphology and many behaviors are influenced by an organism’s sex. Yet none of these traits defines sex. Sex is an organism-level reproductive class anchored to the type of gamete that organism has the biological function to produce. Treating upstream regulators (e.g., SRY activity, hormonal milieu) or downstream outcomes (e.g., dimorphic morphology, behavior) as coequal “levels” of sex is a level-of-analysis error.
Moreover, the multilevel account inherits the same circularity as the polythetic model. Traits are labeled “male-typical” or “female-typical” only because they correlate with organisms already identified as male or female—an identification that, in anisogamous species, is made ultimately by reference to gametes. Once that reference is removed, the typology loses its interpretive footing. As a descriptive framework to integrate genetic, endocrine, and morphological findings in clinical differential diagnosis, the multilevel schema has pragmatic value; as a definition of sex, it is incoherent.
Conclusion
This commentary advances a simple claim with broad consequences: In anisogamous organisms, the sexes—male and female—are functional classes defined by the type of gamete an individual has the biological function to produce (Bogardus, 2025). Males have the biological function to produce sperm; females have the biological function to produce ova (Parker et al., 1972). That definition is universal across all anisogamous taxa. Much contemporary confusion arises from conflating how sex is determined (i.e., how sex develops) with how sex is defined (what sex is), and from conflating upstream determinant and downstream correlates of sex with sex itself. On this account, aneuploidies and DSDs describe variation in development or function within the two sexes; “mating types” belong to isogamous systems and are compatibility classes, not sexes; and “multivariate” or “spectrum” depictions quantify trait variation within and between the two sexes without altering the number of sexes.
The scientific value of clear and precise definitions is enormous (Dawkins, 2025). A gamete-based definition prevents error propagation across comparative biology, physiology, ecology, and medicine. It preserves the interpretability of sex-linked phenomena—sexual selection, dimorphism, and life-history trade-offs—and maintains conceptual discipline by keeping determination mechanisms (e.g., SRY pathways, ZW systems, temperature-dependent determination, social cues) in their proper explanatory lane. It also secures cross-taxon coherence: Whether a species is gonochoric or hermaphroditic, and whether determination is chromosomal, environmental, or social, “male” and “female” remain meaningfully comparable because those terms are anchored to reproductive function rather than to a bundle of traits that shift widely from taxa to taxa.
The societal and ethical stakes are also significant. Accurate biology is distinct from questions of dignity, rights, and how we treat one another. Policy disputes should not be adjudicated by redefining—or defining away—the reproductive realities that make sex a useful scientific concept in the first place. When categories are blurred for nonscientific reasons, we invite downstream harms: muddled clinical protocols, compromised epidemiology, eroding and/or conflicting legal protections, and diminished public trust in science.
Across anisogamous taxa, males and females are defined by gametic dimorphism. Proposals to redefine sex in terms of karyotypes, secondary sexual characteristics, behavior, or other correlates are incoherent and invariably presuppose this foundation, because the categories “male” and “female” are intelligible only by reference to sperm and ova.
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LOL. She's basically just an English Lit professor, pretending to lecture biologists about biology, becuase "mUh TrAnS eXpErIeNcE!!"
How could four accomplished and qualified professors produce such unadulterated rubbish?
By: Alex Byrne
Published: Mar 14, 2024
“Computing is not binary” would be a silly slogan—binary computer code underpins almost every aspect of modern life. But other kinds of binaries are decidedly out of fashion, particularly where sex is concerned. “Biology is not binary” declares the title of an essay in the March/April issue of American Scientist, a magazine published by Sigma Xi, the science and engineering honor society. Sigma Xi has a storied history, with numerous Nobel-prize-winning members, including the DNA-unravellers Francis Crick and James Watson, and more recently Jennifer Doudna, for her work on CRISPR/Cas9 genome editing. The essay is well-worth critical examination, not least because it efficiently packs so much confusion into such a short space.
Another reason for examining it is the pedigree of the authors—Kate Clancy, Agustín Fuentes, Caroline VanSickle, and Catherine Clune-Taylor. Clancy is a professor of anthropology at the University of Illinois, Urbana-Champaign; Fuentes is a professor of anthropology at Princeton, and Clune-Taylor is an assistant professor of gender and sexuality studies at that university; VanSickle is an associate professor of anatomy at Des Moines. Clancy’s Ph.D. is from Yale, Fuentes’ is from UC Berkeley, and VanSickles’ is from Michigan. Clune-Taylor is the sole humanist: she has a Ph.D. in philosophy from Alberta, with Judith Butler as her external examiner. In short, the authors are not ill-educated crackpots or dogmatic activists, but top-drawer scholars. Their opinions matter.
Let’s talk about sex, baby
Before wading into the essay’s arguments, let’s look at the context, as noted in the second paragraph. “Last fall,” the authors write, “the American Anthropological Association made headlines after removing a session on sex and gender from its November 2023 annual conference.” The session’s cancellation was covered by the New York Times as well as international newspapers, and it eventually took place under the auspices of Heterodox Academy. (You can watch the entire event here.) Scheduled for the Sunday afternoon “dead zone” of the five-day conference, when many attendees leave for the airport, the title was “Let’s Talk About Sex, Baby: Why biological sex remains a necessary analytic category in anthropology.” The lineup was all-female, and included the anthropologists Kathleen Lowrey and Elizabeth Weiss. According to the session description, “With research foci from hominin evolution to contemporary artificial intelligence, from the anthropology of education to the debates within contemporary feminism about surrogacy, panelists make the case that while not all anthropologists need to talk about sex, baby, some absolutely do.”
Nothing evidently objectionable here, so why was it cancelled? The official letter announcing that the session had been removed from the program, signed by the presidents of the AAA and CASCA (the Canadian Anthropology Society), explained:
The reason the session deserved further scrutiny was that the ideas were advanced in such a way as to cause harm to members represented by the Trans and LGBTQI of the anthropological community as well as the community at large.
Why “the Trans” were double-counted (the T in LGBTQI) was not clear. And although ideas can harm, a handful of academics speaking in the Toronto Convention Centre are unlikely to cause much. In any event, the authors of “Biology is not binary” seem to think that the panelists’ errors about sex warranted the cancellation, not the trauma their words would bring to vulnerable anthropologists. “We were glad,” they say, “to see the American Anthropological Association course-correct given the inaccuracy of the panelists’ arguments.”
Never mind that no-one had heard the panelists’ arguments—what were these “inaccuracies”? The panelists, Clancy and her co-authors report, had claimed that “sex is binary,” and that “male and female represent an inflexible and infallible pair of categories describing all humans.”
“Biology is not binary” is not off to a promising start. Only one of the cancelled panelists, Weiss, has said anything about sex being binary in her talk abstract, and even that was nuanced: “skeletons are binary; people may not be.” No one had claimed that the two sex categories were “inflexible” or “infallible,” which anyway doesn’t make sense. (This is one example of the essay’s frequent unclarity of expression.) Neither had anyone claimed that every single human falls into one sex category or the other.
Probably the real reason the proposed panel caused such a stir was that it was perceived (in Clancy et al.’s own words) as “part of an intentional gender-critical agenda.” And, to be fair, some of the talks were “gender-critical,” for instance Silvia Carrasco’s. (Carrasco’s views have made her a target of activists at her university in Barcelona.) Still, academics can’t credibly cancel a conference session simply because a speaker defends ideas that bother some people, hence the trumped-up charges of harm and scientific error.
Although Clancy et al. misleadingly characterize the content of the cancelled AAA session, their essay might yet get something important right. They argue for four main claims. First, “sex is not binary.” Second, “sex is culturally constructed.” Third, “defining sex is difficult.” And, fourth, there is no one all-purpose definition of sex—it depends “on what organism is being studied and what question is being asked.”
Let’s go through these in order.
“Sex is not binary”
When people say that sex is binary, they sometimes mean that there are exactly two sexes, male and female. Sometimes they mean something else: the male/female division cuts humanity into two non-overlapping groups. That is, every human is either male (and not female), or female (and not male). These two interpretations of “Sex is binary” are different. Perhaps there are exactly two sexes, but there are some humans who are neither male nor female, or who are both sexes simultaneously. In that scenario, sex is binary according to the first interpretation, but not binary according to the second. Which of the two interpretations do Clancy et al. have in mind?
At least the essay is clear on this point. The “Quick Take” box on the first page tells us that the (false) binary thesis is that “male and female [are] the only two possible sex categories.” And in the text the authors say that “plenty of evidence has emerged to reject” the hypothesis that “there are only two sexes.” (Here they mystifyingly add “…and that they are discrete and different.” Obviously if there are two sexes then they are different.)
If there are not exactly two sexes, then the number of sexes is either zero, one, or greater than two. Since Clancy et al. admit that “categories such as ‘male’ and ‘female’…can be useful,” they must go for the third option: there are more than two sexes. But how many? Three? 97? In a striking absence of curiosity, the authors never say.
In any case, what reason do Clancy et al. give for thinking that the number of sexes is at least three? The argument is in this passage:
[D]ifferent [“sex-defining”] traits also do not always line up in a person’s body. For example, a human can be born with XY chromosomes and a vagina, or have ovaries while producing lots of testosterone. These variations, collectively known as intersex, may be less common, but they remain a consistent and expected part of human biology.
So the idea that there are only two sexes…[has] plenty of evidence [against it].
However, this reasoning is fallacious. The premise is that some (“intersex”) people do not have enough of the “sex-defining” traits to be either male or female. The conclusion is that there are more than two sexes. The conclusion only follows if we add an extra premise, that these intersex people are not just neither male nor female, but another sex. And Clancy et al. do nothing to show that intersex people are another sex.
What’s more, it is quite implausible that any of them are another sex. Whatever the sexes are, they are reproductive categories. People with the variations noted by Clancy et al. are either infertile, for example those with Complete Androgen Insensitivity Syndrome (CAIS) (“XY chromosomes and a vagina”), or else fertile in the usual manner, for example many with Congenital Adrenal Hyperplasia (CAH) and XX chromosomes (“ovaries while producing lots of testosterone,” as Clancy et al. imprecisely put it). One study reported normal pregnancy rates among XX CAH individuals. Unsurprisingly, the medical literature classifies these people as female. Unlike those with CAIS and CAH, people who belonged to a genuine “third sex” would make their own special contribution to reproduction.
“Sex is culturally constructed”
“Biology is not binary” fails to establish that there are more than two sexes. Still, the news that sex is “culturally constructed” sounds pretty exciting. How do Clancy et al. argue for that?
There is a prior problem. Nowhere do Clancy et al. say what “Sex is culturally constructed” means. What’s more, the essay thoroughly conflates the issue of the number of sexes with the issue about cultural construction. Whatever “cultural construction” means, presumably culture could “construct” two sexes. (The Buddhas of Bamiyan in Afghanistan were literally constructed, and there were exactly two of them.) Conversely, the discovery of an extra sex would not show that sex was culturally constructed, any more than the discovery of an extra flavor of quark would show that fundamental particles are culturally constructed.
Clancy et al. drop a hint at the start of the section titled “Sex is Culturally Constructed.” “Definitions and signifiers of gender,” they say, “differ across cultures… but sex is often viewed as a static, universal truth.” (If you want to know what they mean by “gender,” you’re out of luck.) That suggests that the cultural construction of sex amounts to the “definitions and signifiers” of sex differing between times and places. This is confirmed by the following passage: “[T]here is another way we can see that sex is culturally constructed: The ways collections of traits are interpreted as sex can and have differed across time and cultures.” What’s more, in an article called “Is sex socially constructed?”, Clune-Taylor says that this (or something close to it) is one sense in which sex is socially constructed (i.e. culturally constructed).
The problem here is that “Sex is culturally constructed” (as Clancy et al. apparently understand “cultural construction”) is almost trivially true, and not denied by anyone. If “X is culturally constructed” means something like “Ideas of X and theories of X change between times and places,” then almost anything which has preoccupied humans will be culturally constructed. Mars, Jupiter and Saturn are culturally constructed: the ancients thought they revolved around the Earth and represented different gods. Dinosaurs are culturally constructed: our ideas of them are constantly changing, and are influenced by politics as well as new scientific discoveries. Likewise, sex is culturally constructed: Aristotle thought that in reproduction male semen produces a new embryo from female menstrual blood, as “a bed comes into being from the carpenter and the wood.” We now have a different theory.
Naturally one must distinguish the claim that dinosaurs are changing (they used to be covered only in scales, now they have feathers) from the claim that our ideas of dinosaurs are changing (we used to think that dinosaurs only have scales, now we think they have feathers). It would be fallacious to move from the premise that dinosaurs are culturally constructed (in Clancy et al.’s sense) to the conclusion that dinosaurs themselves have changed, or that there are no “static, universal truths” about dinosaurs. It would be equally fallacious to move from the premise that sex is culturally constructed to the claim that there are no “static, universal truths” about sex. (One such truth, for example, is that there are two sexes.) Nonetheless, Clancy et al. seem to commit exactly this fallacy, in denying (as they put it) that “sex is…a static, universal truth.”
To pile falsity on top of fallacy, when Clancy et al. give an example of how our ideas about sex have changed, their choice could hardly be more misleading. According to them:
The prevailing theory from classical times into the 19th century was that there is only one sex. According to this model, the only true sex is male, and females are inverted, imperfect distortions of males.
This historical account was famously defended in a 1990 book, Making Sex, by the UC Berkeley historian Thomas Laqueur. What Clancy et al. don’t tell us is that Laqueur’s history has come under heavy criticism; in particular, it is politely eviscerated at length in The One-Sex Body on Trial, by the classicist Helen King. It is apparent from Clune-Taylor’s other work that she knows of King’s book, which makes Clancy et al.’s unqualified assertion of Laqueur’s account even more puzzling.
“Defining sex is difficult”
Aristotle knew there were two sexes without having a satisfactory definition of what it is to be male or female. The question of how to define sex (equivalently, what sex is) should be separated from the question of whether sex is binary. So even if Clancy et al. are wrong about the number of sexes, they might yet be right that sex is difficult to define.
Why do they think it is difficult to define? Here’s their reason:
There are many factors that define sex, including chromosomes, hormones, gonads, genitalia, and gametes (reproductive cells). But with so many variables, and so much variation within each variable, it is difficult to pin down one definition of sex.
Readers of Reality’s Last Stand will be familiar with the fact that chromosomes and hormones (for example) do not define sex. The sex-changing Asian sheepshead wrasse does not change its chromosomes. Interestingly, the sex hormones (androgens and estrogens) are found in plants, although they do not appear to function as hormones. How could the over-educated authors have written that “there are many factors that define sex,” without a single one of them objecting?
That question is particularly salient because the textbook account of sex is in Clancy et al.’s very own bibliography. In the biologist Joan Roughgarden’s Evolution’s Rainbow there’s a section called “Male and Female Defined.” If you crack the book open, you can’t miss it.
Roughgarden writes:
To a biologist, “male” means making small gametes, and “female” means making large gametes. Period! By definition, the smaller of the two gametes is called a sperm, and the larger an egg. Beyond gamete size, biologists don’t recognize any other universal difference between male and female.
“Making” does not mean currently producing, but (something like) has the function to make. Surely one of Clancy et al. must have read Roughgarden’s book! (Again from her other work we know that Clune-Taylor has.) To avoid going round and round this depressing mulberry bush again, let’s leave it here.
“Sex is defined in a lot of ways in science”
Perhaps sex is not a single thing, and there are different definitions for the different kinds of sex. The standard gamete-definition of sex is useful for some purposes; other researchers will find one of the alternative definitions more productive. Clancy et al. might endorse this conciliatory position. They certainly think that a multiplicity of definitions is good scientific practice: “In science, how sex is defined for a particular study is based on what organism is being studied and what question is being asked.”
Leaving aside whether this fits actual practice, as a recommendation it is wrong-headed. Research needs to be readily compared and combined. A review paper on sexual selection might draw on studies of very different species, each asking different questions. If the definition of sex (male and female) changes between studies, then synthesizing the data would be fraught with complications and potential errors, because one study is about males/females-in-sense-1, another is about males/females-in-sense-2, and so on.
Indeed, “Biology is not binary” itself shows that the authors don’t really believe that “male” and “female” are used in science with multiple senses. They freely use “sex,” “male,” and “female” without pausing to disambiguate, or explain just which of the many alleged senses of these words they have in mind. If “sex is defined a lot of ways in science” then the reader should wonder what Clancy et al. are talking about.
In an especially odd passage, they write that the “criteria for defining sex will differ in studies of mushrooms, orangutans, and humans.” That is sort-of-true for mushrooms, which mate using mating types, not sperm and eggs. (Mating types are sometimes called “sexes,” but sometimes not.) However, it’s patently untrue for orangutans and humans, as the biologist Jerry Coyne points out.
Orangutans had featured earlier in the saga of the AAA cancellation, when Clancy and Fuentes had bizarrely suggested that the “three forms of the adult orangutan” present a challenge to the “sex binary,” seemingly forgetting that these three forms comprise females and two kinds of males. Kathleen Lowrey had some fun at their expense.
As if this tissue of confusion isn’t enough, Clancy et al. take one final plunge off the deep end. After mentioning osteoporosis in postmenopausal women, they write:
[P]eople experiencing similar sex-related conditions may not always fit in the same sex category. Consider polycystic ovary syndrome (PCOS), a common metabolic condition affecting about 8 to 13 percent of those with ovaries, which often causes them to produce more androgens than those without this condition. There are increasing numbers of people with PCOS who self-define as intersex, whereas others identify as female.
They seem to believe that two people with PCOS might not “fit in the same sex category.” That is, one person could be female while the other isn’t, with this alchemy accomplished by “self-definition.” PCOS, in case you were wondering, is a condition that only affects females or, in the approved lingo of the Cleveland Clinic, “people assigned female at birth.”
How could four accomplished and qualified professors produce such—not to mince words—unadulterated rubbish?
There are many social incentives these days for denouncing the sex binary, and academics—even those at the finest universities—are no more resistant to their pressure than anyone else. However, unlike those outside the ivory tower, academics have a powerful arsenal of carefully curated sources and learned jargon, as well as credentials and authority. They may deploy their weapons in the service of—as they see it—equity and inclusion for all.
It would be “bad science,” Clancy et al. write at the end, to “ignore and exclude” “individuals who are part of nature.” In this case, though, Clancy et al.’s firepower is directed at established facts, and the collateral damage may well include those people they most want to help.
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About the Author
Alex Byrne is a Professor of Philosophy at the Massachusetts Institute of Technology (MIT) in the Department of Linguistics and Philosophy. His main interests are philosophy of mind (especially perception), metaphysics (especially color) and epistemology (especially self-knowledge). A few years ago, Byrne started working on philosophical issues relating to sex and gender. His book on these topics, Trouble with Gender: Sex Facts, Gender Fictions, is now available in the US and UK.
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The whole "social construction," "cultural construction" thing is idiotic.
Not only does it mean you would be a different sex in a different society/culture, but it becomes necessary that cross-cultural/cross-societal reproduction is fraught with complications.
