Debunking the ACLU's '4 Myths About Trans People'

I have always been interested in the “debunking” genre. I’ve seen probably every episode of Mythbusters, and the immense joy I have experienced watching James “The Amazing” Randi expose charlatans peddling snake-oil and paranormal woo woo is almost unparalleled. Books like Donald Prothero’s Evolution: What the Fossils Say and Why It Matters, which systematically debunked many Young Earth Creationist claims about how the Grand Canyon was formed, keep me glued to their pages.

My interest in the “debunking” likely stems from my interest in the truth. I don’t want to be wrong about any issue for a moment longer than absolutely necessary, and so I’ve always eagerly sought out books and papers purporting to systematically discredit my own closely-held beliefs. This is likely why I eventually became a scientist. Indeed, the scientific method is basically an instruction manual for debunking, and the progress of science can be summarized as one good debunking after another.

So, when I opened Twitter and saw the ACLU’s thread and accompanying essay purporting to “DEBUNK” several myths about trans athletes, I was excited to dig in. Maybe this would finally change my mind on an issue for which I have been repeatedly beaten over the head for wrongthink. However, what I found was instead a list of unsupported assertions and distortions that have unfortunately become the norm for many once-great organizations and institutions.

Given the ACLU’s wide influence and assumed prestige, I thought it would be valuable to inspect each of the ACLU’s claims and offer, if necessary, a scientifically-informed critique. And since President Biden has recently signed an Executive Order mandating athletes to be allowed to compete according to their gender identity instead of their biological sex, this is an issue that isn’t going away any time soon. 

The first “myth” that the ACLU attempts to debunk is actually a series of three claims that “sex is binary, apparent at birth, and identifiable through singular biological characteristics.” I’ll address these individually.

Is sex binary? The use of the term “binary” is one that many seem to trip over. According to the dictionary definition, binary means “consisting of, indicating, or involving two.” As a biologist, I can confidently say this definition accurately describes biological sex. That is because the sex of an individual refers to one of two—and only two—functional roles that an individual may play in sexual reproduction. Males are defined as the sex that produces small, motile gametes (sperm), and females produces large, sessile gametes (ova). There is no third gamete between sperm and ova, and therefore there is no third biological sex apart from males and females. Intersex is an umbrella term that refers to external sex ambiguity or a mismatch between internal sexual anatomy and external phenotype, but it is not a third sex.

It becomes apparent, however, that to many activists the phrase “sex is binary” is interpreted as meaning that every single individual can be categorized as either male or female. While it may be true that not every individual may be classifiable as either male or female, this does not refute the claim that sex is binary, only that not every individual may have a determinable sex. Sex is binary in humans because—in line with the dictionary definition of binary—it “consists of” and “involves” two and only two sexes.

Is sex apparent at birth? For the overwhelmingly vast number of people, yes. The prevalence of infants presenting with intersex conditions or disorders/differences of sexual development (DSDs) is around 0.2 percent (about 1 in 500).

However, DSD is a much broader category than intersex and does not necessarily denote sex ambiguity. For instance, Klinefelter (XXY) males and Turner (X0) females are not sexually ambiguous at all, yet are often considered DSDs. When we use a clinically-relevant definition of intersex such as “conditions in which chromosomal sex is inconsistent with phenotypic sex, or in which the phenotype is not classifiable as either male or female” the rate of individuals whose sex does not appear obvious at birth decreases by more than an order of magnitude from 0.2 percent to 0.018 percent (~1 in 5500).

So, to answer the question “is sex apparent at birth?”—yes, for almost everybody. The fact that 0.018 percent of babies may appear sexually ambiguous potentially resulting in misclassification of sex at birth doesn’t mean that the current classification system is wrong or flawed. It just means that biology can be messy at times. Though a misclassification rate of only 0.018 percent likely places sex among the most consistent phenomena in all the life sciences.


Is sex identifiable through singular biological characteristics? It is common to claim that an individual’s sex is a statistical property that can only be hinted at (and never determined absolutely) by observing many traits simultaneously. This, however, is based on an inversion of a somewhat esoteric fallacy known as the univariate fallacy. This fallacy can be summed up as the insistence that categories must be cleanly separable and reducible to a single essential factor in order for them to be considered real or “natural” categories. The ACLU is suggesting that biological sex can’t be reduced to a single (univariate) factor, but is instead composed of many (multivariate) phenomena.

While it may be true that some phenomena, such as sex differences in neuroanatomy, facial features, and hand morphology are multivariate phenomena that can’t be reduced down to single factors, biological sex is not a multivariate phenomenon. There are many properties associated with one’s sex, such as hormone profiles and chromosomes, but these do not define an individual’s sex. Rather, we identify an individual’s biological sex by their primary sex organs (testes vs ovaries), as these organs are what form the basis for the type of gamete (sperm vs ova) an individual may potentially produce.

Despite what the ACLU claims, biological sex can be reduced down to a single characteristic: gonads. But while rare edge cases may exist, this does not make our present understanding of biological sex useless or arbitrary.

The second “myth” that the ACLU wants you to believe has been debunked is the claim that “trans athletes’ physiological characteristics provide an unfair advantage over cis athletes.” The reasons they give are that both cis and trans athletes vary in athletic ability, and that trans athletes don’t always win.

While it is true that the distribution between males and females in athletically-relevant traits like size, speed, and strength do overlap, this is hardly evidence that male athletes who identify as women do not possess an unfair athletic advantage over female athletes. The distribution of size, speed, and strength between children and adults also exhibits overlap, yet no sane person would argue that adults don’t have an unfair advantage over children, and we must therefore allow adults to compete in children’s sports leagues and events. This “overlap therefore no advantage” line of argumentation could also be used to absurdly claim that heavyweight boxers do not have an advantage over featherweight boxers.

Additionally, the fact that trans athletes don’t always or “consistently” win against female competitors is not good evidence that no unfair advantage exists. Whether or not an individual possesses an unfair advantage is not determined in relation to other competitors, but rather in relation to how that individual would have performed otherwise. For instance, a low-ranking athlete could start taking performance enhancing drugs (PEDs) that causes them to move up in rank, yet still never place first. The fact that they’re still not winning any competitions does not mean the PEDs have not conferred onto them an unfair advantage, because they are performing better than they would have had they not taken PEDs.

Allowing males to compete against females is unfair not because they always win (they don’t), but because they perform better than they would have had they, like female athletes, not gone through male puberty. Though there is good evidence for male performance advantages in children as well.

All this is well and good assuming biological males actually have a physiological advantage over females, but do they? Yes, and on every metric for which there is data for both untrained/moderately trained individuals as well as for elite athletes. A 2021 review by Drs. Emma N. Hilton and Tommy R. Lundberg has compiled the data.

As shown in Hilton and Lundberg’s review:

The smallest performance gaps were seen in rowing, swimming and running (11–13%), with low variation across individual events within each of those categories. The performance gap increases to an average of 16% in track cycling, with higher variation across events (from 9% in the 4000 m team pursuit to 24% in the flying 500 m time trial). The average performance gap is 18% in jumping events (long jump, high jump and triple jump). Performance differences larger than 20% are generally present when considering sports and activities that involve extensive upper body contributions. The gap between fastest recorded tennis serve is 20%, while the gaps between fastest recorded baseball pitches and field hockey drag flicks exceed 50%.

Moreover, even after testosterone suppression, the performance gap between males and females is only minimally reduced.

The data presented here demonstrate that superior anthropometric, muscle mass and strength parameters achieved by males at puberty, and underpinning a considerable portion of the male performance advantage over females, are not removed by the current regimen of testosterone suppression permitting participation of transgender women in female sports categories. Rather, it appears that the male performance advantage remains substantial.

Thus, in light of the most recent and robust evidence, the ACLU’s claim that transgender athletes’ physiological characteristics do not provide them with an unfair advantage over females is entirely false.

The third “myth” that the ACLU purports to have debunked is the claim that “the participation of trans athletes hurts women.” This is the most vague, as it is unclear what they mean by “hurt.” What is clear is that while they believe that testing a small number of people to verify their sex is unbearably hurtful to women, allowing males to potentially outcompete females in women’s sporting events and for athletic scholarships apparently does not hurt biologically female women in any way.

The ACLU has also muddled the two very distinct issues of policies for addressing DSD/intersex athletes and those for trans athletes. DSD policies specify the criteria of inclusion for athletes born with intersex conditions. Since some DSDs may result in sex ambiguity, DSD policies are necessary in order to specify the criteria to compete as females. There are valid debates to be had about where lines of inclusion should be drawn, but if you believe that there should be a protected female category in sports, you agree that a line must be drawn somewhere, otherwise the female category ceases to be “protected.”

Transgender is completely distinct from intersex. Whereas intersex people have developmental conditions that result in some degree of sex ambiguity or mixed characteristics, the vast majority of transgender individuals have no such condition. The issue surrounding trans athletes in sports concerns unambiguously male athletes who simply identify as women and wish to compete in women’s and girl’s sporting events. Given that it is one’s biological sex, not gender identity, that directly influences athletic performance, allowing male athletes who identify as women to compete against female athletes raises serious concerns of fairness and safety.

The ACLU’s fourth and final “myth” they claim to have debunked is the notion that “trans students need separate teams.” The suggestion that trans athletes should compete in leagues and events specifically designed for trans athletes is commonly suggested as an alternative to allowing males who identify as women to compete against female athletes. Since male athletes cannot compete fairly alongside female athletes, and since trans women who take puberty blocking drugs or cross-sex hormones would likely be disadvantaged in competition against other male athletes, it would seem appropriate to have them compete in a separate trans category.

While the ACLU suggests separate leagues and events may cause trans people to “experience detrimental effects to their physical and emotional wellbeing,” they seem entirely unconcerned with the physical and emotional wellbeing of the female athletes they would be subjecting to unfair competition. Sex-segregated sports categories were not created to “affirm” people’s identities; they were created to ensure fair competition and safety for female athletes.

The ACLU then proceeds to create a faux enemy of people who are trying to “exclude a subset of girls from sports.” This is a complete distortion. Nobody is trying to exclude trans athletes from sports. Rather, people simply want trans athletes to compete in leagues and events that align with their biological sex rather than their gender identity. This is because it’s biological sex, not gender identity, that is relevant for sports.

Despite what the ACLU would have you believe, there are in fact only two biological sexes, sex is almost always apparent at birth, and sex can be determined by an individual’s gonads. Furthermore, until recently we only had our eyes and common sense at our disposal to tell us that the inclusion of trans women (biological males) in female sports would not be fair to female athletes. Fortunately for us the science has now caught up with common sense, and so it no longer remains possible to reasonably maintain the ACLU’s position that trans women don’t have an unfair advantage over female athletes.

Far from actually “debunking” any myths with evidence and reason, the ACLU has simply responded to several valid concerns surrounding women’s rights with a series of scientifically illiterate political slogans. This does nothing to advance the civil liberties of trans people or women, and instead likely only increases animosity toward the vulnerable groups they claim to defend.


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