Over the past few weeks there have been a number of articles in mainstream publications insisting that concerns surrounding biologically male athletes competing as females has no basis in science.
For instance, in a February 3rd Twitter thread purporting to debunk several “myths” about trans athletes and sports, the ACLU recently claimed that banning biologically male athletes who identify as girls from competing in the female category is “unscientific.” This week, Scientific American published a piece titled “Trans Girls Belong on Girls’ Sports Teams” by psychiatry fellow Jack Turban, where he claimed “there is no scientific case” for keeping male athletes out of the female category. And, a few days later, NPR published an interview with Dr. Eric Vilain, a clinician and the director of the Center for Gender-Based Biology at the University of California, Los Angeles, claiming such bans are “not based in science.”
Given Dr. Vilain’s previous comments regarding the nature of biological sex (he believes sex is a “spectrum”), this comes as no surprise. In a 2015 Nature article titled “Sex Redefined,” Vilain is quoted as saying, “My feeling is that since there is not one biological parameter that takes over every other parameter, at the end of the day, gender identity seems to be the most reasonable parameter.” In other words, Villain believes that biological sex is a multivariate phenomenon, and since he believes sex can’t be pinned down to a single objective variable, then we might as well abandon objectivity altogether and rely solely on subjective gender identity to classify people.
As I mentioned in a previous post, this argument is an inversion of a fallacy known as the univariate fallacy.
[The univariate 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… 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.
Since Vilain doesn’t believe sex is an objective variable, it’s no wonder he does not see any problem with male athletes competing against females: if males and females are just arbitrary groupings, as he appears to believe, on what basis can we exclude anyone from a sex category?
Vilain is an issue in these debates because he has a very long and extensive publication record, yet on the issue of biological sex and gender identity it is clear that his political ideology takes precedence over the facts. In other words, his credentials are much more impressive than his arguments, but that is only apparent to those who understand the biology well enough to see what he’s doing.
What follows is a reproduction of the NPR interviewer’s questions and Vilain’s responses, followed by my analysis. Please evaluate my arguments, check my sources, and decide for yourself who appears to be making more sense.
Supporters of these bills say they are meant to eliminate any competitive advantage that transgender athletes may have. So I'd like to ask you if there is data on this and what does it show?
We know that men have, on average, an advantage in performance in athletics of about 10% to 12% over women, which the sports authorities have attributed to differences in levels of a male hormone called testosterone. But the question is whether there is in real life, during actual competitions, an advantage of performance linked to this male hormone and whether trans athletes are systematically winning all competitions. The answer to this latter question, are trans athletes winning everything, is simple — that's not the case. And higher levels of the male hormone testosterone are associated with better performance only in a very small number of athletic disciplines: 400 meters, 800 meters, hammer throw, pole vault — and it certainly does not explain the whole 10% difference.
And lastly, I would say that every sport requires different talents and anatomies for success. So I think we should focus on celebrating this diversity, rather than focusing on relative notions of fairness. For example, the body of a marathon runner is extremely different from the body of a shot put champion, and a transwoman athlete may have some advantage on the basketball field because of her height, but would be at a disadvantage in gymnastics. So it's complicated.
Here Vilain acknowledges the fact that males have a marked performance advantage over females of about 10-12%. However, Vilain claims that the real question is “whether there is in real life, during actual competitions, an advantage of performance linked to this male hormone.” He claims that there is only evidence that testosterone is related to performance in just a few events.
But we do know that levels of circulating testosterone is what produces this performance gap. A 2018 study by Handelsman et al. titled “Circulating Testosterone as the Hormonal Basis of Sex Differences in Athletic Performance” states:
There is a wide sex difference in circulating testosterone concentrations and a reproducible dose-response relationship between circulating testosterone and muscle mass and strength as well as circulating hemoglobin in both men and women. These dichotomies largely account for the sex differences in muscle mass and strength and circulating hemoglobin levels that result in at least an 8% to 12% ergogenic advantage in men. Suppression of elevated circulating testosterone of hyperandrogenic athletes results in negative effects on performance, which are reversed when suppression ceases.
Furthermore, Vilain is ignoring a fundamental aspect of testosterone, namely its role in guiding bodies irreversibly through male puberty. Vilain is focusing only on present levels of circulating testosterone and completely ignoring the massive influence that past testosterone levels have on body development that are not reversed when hormone levels are reduced. Reducing testosterone levels in males who have already experienced male puberty will not influence one’s height, arm length, hand size, or hip morphology, and the best evidence from two independent reviews indicates that hormone suppression in post pubertal males results in only a negligible reduction in muscle mass and strength.
Villain also believes that if male athletes who identify as female had an advantage over biologically female athletes then they would be “systematically winning all competitions.” But this demonstrates a complete misunderstanding of what it means to have an advantage. An advantage isn’t measured strictly in relation to other athletes, but rather in relation to how you would have performed otherwise without some variable in question, which in this case is the effects of experiencing male puberty.
To illustrate: if person A is 10% faster than I am, and taking performance enhancing drugs (PEDs) make me only 5% faster, the fact that I’ll still lose in a footrace to person A doesn’t mean I do not have an unfair advantage, because my advantage is measured in relation to my speed without PEDs, not in relation to person A’s running speed.
Simply put, there are many more biological females in female sports than there are males who identify as female. The chances that any male chosen at random will be, say, faster than every female in a track competition—which is already a non-random sample of particularly fast females—may be low. Because of this we would not expect trans athletes to be “systematically winning all competitions.” But that does not mean they do not have an advantage.
Furthermore, Vilain’s claim that testosterone only influences performance in a “very small number of athletic disciplines” such as the 400 meters, 800 meters, hammer throw, pole vault, is guilty of a sampling bias. Specifically, Vilain is only looking at the influence of testosterone levels within female athletes, who all have very similar levels of testosterone and history of testosterone, and not doing the proper comparison which is to compare females to male athletes, because that’s what we are actually comparing when we are talking about the advantages of male athletes who identify as female competing in the female category.
As an illustrative example in another context, consider the fact that there is no relationship between height and points per game in the NBA. From this fact you might conclude that height is not an important trait in basketball. But this would be incorrect, since you’re testing for a relationship among those few individuals who already had what it took to play in the NBA. When you take a step back and survey the population as a whole, you find that the average height of an NBA basketball player is 6’7’’ (2.01m), which is about 10’’ (25.4cm) taller than the average male. What this tells us is that height matters a lot in basketball generally and for making it to the NBA, but among NBA players it is not the sole determinant of scoring ability.
Lastly, Vilain states that “every sport requires different talents and anatomies for success.” I refer to this as the “all shapes and sizes” argument. It asserts that since male and female bodies have a lot of overlap—we all know some really tall females!—that fairness cannot really be determined based on one’s sex. While it is true that there is overlap in morphology between males and females, and that different traits are more or less important depending on the sport, it nevertheless remains a plain fact that in every sport the most elite female athletes of all time can be beaten by many thousands of males, and even many teenage boys.
There is no rule preventing female athletes from playing in the NBA, NFL, MLB, or NHL. These leagues are open to anyone who can compete. It is no coincidence that no female has ever had the proper “anatomies for success” in these leagues. At the extreme tail end of human athletic ability, there are simply no females.
In your view, because you have advised the NCAA on this as well as the International Olympic Committee, is there a reason to limit the participation of transgender athletes at the high school level or perhaps even at the collegiate level? Is there any good faith reason to do that?
I don't think so. First, I will say that there is a huge difference between elite sports and sports in schools. Sports in schools are supposed to be primarily about inclusivity, setting individual goals, collective goals and well-being. And it is not supposed to be about crushing the competition. But if we want to make it this way, then the rules still need to be inclusive, or at least not come up with arguments that are not based in science. So one of the major issues in school — and of course in the elite world — is that binary categories make it quite difficult to come up with reasonable eligibility regulations. And they do create a lot of frustrations. So one way out of this could be opening up categories. That would be a way to explore different ways, a path to do sports competitions, especially in schools. However, adding categories needs to be well thought out and done with equal access to benefits, such as scholarships. Otherwise, it would create categories of second class citizens, which is certainly not a good thing.
First off, Vilain states that “Sports in schools are supposed to be primarily about inclusivity, setting individual goals, collective goals and well-being. And it is not supposed to be about crushing the competition.” Since when is this the case? Who gets to determine this? Many school sports have try-outs, where only the best prospects make the team. And a school’s best athletes frequently go on to compete at multiple levels against other schools. Frequently, success in high school athletics translates into college scholarships. It simply isn’t the case that the sole purpose of school sports is inclusivity and emotional well-being.
Yes, sports are fun and enjoyment certainly should be part of it, but to suggest that it is the sole purpose is delusional. If you want to just have fun and not take the game or event too seriously, you can join a local recreation league, play with friends in a park, or set individual strength and speed goals. What Vilain completely discounts are the female athletes whose well-being is negatively affected when they are forced to compete against male athletes, or who set individual goals of winning and obtaining a college scholarship.
But Vilain says that even if the purpose was about winning and competition, school sports would still need to be inclusive, and that any arguments for excluding male athletes who identify as female from the female category must be based in science. For the science I refer to these two 2021 reviews that I mentioned in response to Vilain’s first answer. Vilain simply must know these reviews exist.
Vilain is right about one thing though, which is that schools do need to come up with reasonable eligibility criteria for DSD athletes. But just because some intersex conditions may present difficult edge cases doesn’t mean that some criteria are not more reasonable than others. If we agree that female sports should be a protected category, then a line must be drawn somewhere. Failing to draw a line anywhere means the category is not protected.
One of the groups that has come out against these types of laws is the National Women's Law Center. They wrote a brief against a bill in Idaho that seeks to ban transgender girls from participating in youth female sports. And in it, they write, "The law allows anyone for any reason to question whether a student athlete is a woman or girl. And then the student has to verify her gender by undergoing invasive testing, which could include a gynecological exam, blood work or chromosome testing." And one of the plaintiffs was a plaintiff named Jane Doe, who was a cisgender female athlete, but she doesn't normally wear skirts or dresses and has an athletic build. And they're saying that under a law like this, somebody could just ask or insist that this athlete undergo one of these exams to prove her gender, that that's inherently harmful and serves no legitimate purpose. What do you say to that?
You know, it's interesting because in the field of sports, there's a long history of discrimination that targets women that look different. Again, the science of whether testosterone in real life is actually providing an advantage in competition is not clearly established. But more disturbingly is that all these rules at the elite level have affected women — not all women, but women with a Y chromosome. And often, it's triggered by women who look different. So I'm a little disturbed to hear that these issues at the elite level are now reaching the middle and high schools and colleges.
Here Vilain again repeats the completely false claim that “the science of whether testosterone in real life is actually providing an advantage in competition is not clearly established.” As I explained above, this is just plain wrong. The review I linked to above demonstrate a “Strong dose-response relationship between testosterone dose and circulating concentration with muscle mass and strength” in both males and females.
The concluding remarks to this review are as follows:
The available, albeit incomplete, evidence makes it highly likely that the sex difference in circulating testosterone of adults explains most, if not all, the sex differences in sporting performance. This is based on the dose-response effects of circulating testosterone to increase muscle mass and strength, bone size and strength (density), and circulating hemoglobin, each of which alone increases athletic capacity, as well as other possible sex dichotomous, androgen-sensitive contributors such as mental effects (mood, motivation, aggression) and muscle myoglobin content. These facts explain the clear sex difference in athletic performance in most sports, on which basis it is commonly accepted that competition has to be divided into male and female categories.
Vilain also claims that regulations have affected “women with a Y chromosome.” For those unaware, a Y chromosome is the male sex chromosome. It is perfectly reasonable to have rules preventing male athletes with a DSD, like Caster Semenya, from competing in the female category. Different sporting bodies may choose to have different rules for DSD males, and that’s their prerogative, but to simply conflate having a gender identity of “woman” with being biologically female is either ignorant or dishonest.
You helped the NCAA shape their guidelines for the inclusion of transgender athletes in 2011. You also advise the International Olympic Committee on similar issues. What do you look at when determining what makes a certain sport fair, especially given an eye to both fairness and inclusivity?
If we want to think about fairness, we should look first at the principles of the Olympic charter. It says every individual must have the possibility of practicing sport without discrimination of any kind. And in the Olympic spirit, what's true for schools should be true for colleges and should be for the elite level. And there is really a long journey of athletes with gender variations that are facing increasing rulings that are often discriminatory and not based on science. And they should inspire us to consider the full complexity of interpretation of data and cherish our more treasured values, which I would say in science is evidence, and of course embrace inclusivity.
The word “discrimination” is frequently a major stumbling block for trans activists. They appear under the impression that discrimination is synonymous with bad and immoral. But this is an extremely novice take. Not all discrimination is wrong, and in many instances discrimination is necessary. When we decide as a society that we want people with disabilities to be able to obtain handicap placards and have the best parking spots, this requires us to discriminate based on mobility. When our government gives out unemployment checks, they must discriminate based on employment status. Discrimination is just a synonym for being able to distinguish between things, and in order to address injustice we must be able to determine its material basis.
Nobody is telling trans people they’re not allowed to play sports. That simply isn’t happening. All that people like me are insisting upon is that the female category be reserved for female athletes so that females can play on a more equal playing field with other female athletes. A male athlete who identifies as female can still play sports, they simply must do so in the category that aligns with their sex, because it is biological sex, not gender identity, that is relevant to athletic performance. This should not be a controversial position.
While Vilain argues for the ability of male athletes who identify as female to compete against biologically female athletes, he fails to address the central question about why events should be segregated by subjective gender identity in the first place. He seems to take it as a given that it is totally reasonable to segregate sports by subjective identity, yet segregating by objective anatomy is somehow beyond the pale. This is the elephant in the room for activists like Vilain who argue for the inclusion of biologically male trans women and girls in female sports.
Segregating sports by gender identity makes about as much sense as segregating them by political party or Myers-Briggs personality types. These simply have no relevant connection to athletic ability. However, I don’t believe I have ever observed a trans activist argue that sports should not be segregated at all. I’ll leave the reader to ponder why that might be.
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