Caster Semenya of South Africa reacts during the women’s 800-meter round-one heats, on day 12 of the Rio 2016 Olympic Games. Semenya has been the subject of heated controversy — and the victim of breaches of her medical privacy — over the fact that she appears to have certain “male” characteristics. Photo: Shaun Botterill/Getty Images

For those closely following the Olympics, this year’s events have provided something of a crash course on the science of sex differences. That’s largely due to the success of Caster Semenya, a South African track star set to compete in tonight’s 800-meter semifinals, who is widely believed to have an intersex condition that gives her certain “male” characteristics.

As Daniel Engber explains in an excellent Slate rundown:

Among athletes with intersex conditions, none is as prominent nor as magnificently gifted as Semenya. Seven years ago, while still a teenager, she destroyed her rivals in the 800 meters at the track-and-field world championships. Shortly thereafter, a clumsy, ad hoc, and supposedly secret assessment of Semenya’s true biological sex made its way into the press: She’d been found to have internal testes in place of a uterus and ovaries, as well as high levels of testosterone. Semenya addressed the controversy in early 2010: “I have been subjected to unwarranted and invasive scrutiny of the most intimate and private details of my being,” she said.

It is the high level of testosterone that has garnered the most attention from the International Olympic Committee. In the past, Engbar explains, athletic governing bodies would simply swab female athletes’ cheeks and check their saliva for markers of a Y chromosome; if a given athlete had one, she wouldn’t be allowed to compete as a woman (there are intersex people who due to their appearance are labeled females at birth, and go on to live as women, and who have either XY or XXY chromosomes).

But, as it turns out, a Y chromosome doesn’t always confer a biological advantage. While it’s true that female athletes with so-called androgen insensitivity syndrome, which brings with it XY chromosomes, appear to be over-represented in Olympic events, even here things are tricky: “It’s very difficult to say whether AIS confers an athletic advantage,” Rob Ritchie, a urological surgeon who has written about Olympics sex-testing, told Time in 2009. The author of the article, Eben Harrell, continued: “Those who have complete AIS, despite being genetically male, display fewer signs of the presence of testosterone than the average female, who produces and absorbs a small amount of the hormone. There is such a condition as partial AIS, however, in which a person has some sensitivity to testosterone and so develops masculine features — such as larger muscles — alongside feminine features.” So even a set of XY chromosomes is not enough to state, with certainty, that a female athlete enjoys a marked advantage over the competition.



Plus, some female athletes who do appear to have an advantage — “perhaps resulting from a sex-hormone-producing adrenal tumor or a genetic condition such as congenital adrenal hyperplasia,” as Engbar put it — don’t have a Y chromosome.

As a result of this method’s shortcomings, Engbar writes, things eventually graduated to “a more flexible standard for women who had been flagged for testing, relying on a host of factors including each athlete’s internal and external anatomy, psychology, hormone levels, and genetics.” These were the invasive tests Semenya endured, the results of which were leaked without her consent. One focus of this testing has been on athletes’ levels of the “male” hormone, testosterone. For a period, female athletes with raised levels of T (well, technically functional testosterone, but we’ll get to that distinction in a moment) were forced to artificially lower their levels in order to compete in women’s events. “Semenya appears to be a member of [this group],” writes Engbar. “Her performance tailed off in the years that followed — she finished in silver-medal position in the 800 meters at the 2012 Olympics, with a time nearly 2 seconds slower than she’d run in 2009.”

Another high-profile athlete who got swept into the new testing regime, the Indian sprinter Dutee Chand, challenged the testosterone standard, and the Court of Arbitration for Sport ruled in her favor, shelving the standards until at least next year. So in this year’s Olympics, Semenya, Chand, and other female athletes with high levels of T are competing unhindered.

There doesn’t seem to be much disagreement that Semenya and Chand have been treated unfairly by governing bodies that have tried to clumsily cobble together new testing systems and standards on the fly, or that Semenya’s privacy was violated in various ways. Where there is at least some debate is about the question of whether athletes with conditions like Semenya and Chand’s are enjoying an unfair advantage, given that the point of dividing sports by sex is to account for certain biological differences between women and men — differences that are sometimes fuzzy at the level of the average human, but can be heightened at the level of elite athletics. If a woman has enough of the characteristics which would account for a male athlete being faster and stronger than a female one, should she still be able to compete with women who don’t have those characteristics?

During one installment of a regular New Yorker conversation about Olympics track and field between Malcolm Gladwell and Nicholas Thompson, Thompson asked Gladwell whether Semenya should be able to compete in the women’s category. “Of course not!” Gladwell responded. “And why do I say ‘of course not’? Because not a single track-and-field fan that I’m aware of disagrees with me.” But if Gladwell is right, where should the guidelines lie, given the incredible complexity of sex differences? What makes Semenya different from any other top athlete whose biological wiring gives them an advantage — which is to say, from any other top athlete?

To learn more about this controversy, Science of Us spoke with Alice Dreger, the author of Galileo’s Middle Finger: Heretics, Activists, and the Search for Justice in Science (about which I wrote a review-essay, here). Dreger has a long history of working on intersex and intersex-adjacent issues. The former head of the Intersex Society of North America, she has consulted for the International Olympic Committee and the International Association of Athletics Federations, as well as the Canadian Centre for Ethics in Sport. “And in my free time,” she noted, “I dope with testosterone so that I can legitimately buy men’s shaving products, which are cheaper than women’s.” (All links below were added by me.)

My sense is that you agree with what other people have written: that the IOC has done a rather poor job handling this issue. What’s the short explanation for why they’ve had so much trouble here?

They think there is one trait they can use to distinguish males or females in a way that will be fair. There isn’t. For any trait you pick, there is someone for whom it won’t make sense. Also: Males and females are not qualitatively different, they’re quantitatively so, and they overlap. You can’t have what the IOC and other organizations want — the claim that “we’re not determining people’s genders” — while also telling some women they can’t participate as women.

Before we get to the specifics of Semenya, we should get one thing out of the way: All else being equal, having more testosterone — whether from an internal or external “source” — is likely to give you an advantage in many athletic competitions, right? I’ve seen several articles questioning how much of the difference between male and female athletic performance can be attributed to the fact that males produce more testosterone — one of them was in the New York Times, by Rebecca Jordan-Young and Katrina Karkazis. And you responded in a letter to the editor you co-wrote with David Epstein, the author of The Sports Gene.

Yes, testosterone matters. You also have to have the receptors in your cells to react to it. So it does not seem to confer any advantage on women with complete androgen insensitivity syndrome. But for everyone who is androgen-sensitive, testosterone does seem to make a difference. Joanna Harper, a transgender athlete and scientist, has done a nice study of runners who have transitioned male-to-female, showing how dramatically their running times drop with lowering of T.

One of the objections that people like Jordan-Young and Karkazis have is that lowering the T of someone like Caster Semenya will take away a natural advantage. Exactly. It does. That’s proof that T matters. And that’s one thing that really bugs me: The IOC/IAAF says, “You can still play if you let us lower your T,” but the fact is that women who have high T and get it lowered can legally play under the rules, but in fact they can no longer compete adequately. So they lose everything. It’s rather heartbreaking.

I’ve had some folks in the IOC/IAAF say to me, “Yes, but we treated their medical problem.” Please. They didn’t really have medical problems.

So in the case of Semenya, we know: 1) She has a very high level of T; 2) it is likely conferring her an advantage; and 3) she has been subjected to a lot of rather invasive, inhumane testing, as track’s governing bodies have tried to figure out what to “do” about her. Is your stance that nothing should be done? That she’s just a woman with high T, who should enjoy that benefit the same way LeBron James or Marshawn Lynch or anyone else gets to enjoy their athletic freakishness?

I don’t think we officially know 1 or 3. We can infer them, but she hasn’t publicly said very much compared to, say, Dutee Chand, who has very bravely stood up. But we can infer 1, 2, and 3. All women make T. Why should men be allowed to have it without limitations, while women are not?

If the answer is “because we labeled her wrong at birth,” that’s really about sex, and not about gender. And in that case, I think what the IOC and IAAF are doing is not creating a division between men’s and women’s sports, but a division between two biological classes: high T and low T. I’ve told them as much and said they should be honest about it.

There are a few sports in which we have biological classes — wrestling weight classes, for example. There are some sports (not in the Olympics) divided by age from birth — like high-level running, for example. You can do it if you want to do it. You can divide people by biological markers. But if that’s what you’re doing, don’t call it gender divisions. Call it biological testosterone classes.

But isn’t that what a gender division is: a sloppy proxy for a whole constellation of, in part, biological markers? And the problem is, no one ever bothered to figure out exactly what they are or what the boundaries should be, since people wrongly assume it’s always easy to tell?

Gender is a sloppy proxy for a whole constellation of biological markers and lived experiences and cultural norms and, and, and … throw in some capitalism here, in pretty hefty doses, since gender sells as a way to sloppily sell sex. But if the people in charge of sports (who are mostly men) want to use a single biological marker to decide who counts as a woman, they are going to have a very difficult time justifying that — particularly when that marker is something like testosterone, which all women naturally produce. Because it doesn’t make sense for anyone who has the smallest clue about how sex develops and what gender is. Which at this point in history, the IOC and IAAF really do have. So there’s no excuse for still being stupid.

One area where this is bound to get contentious is with the increasing prevalence and visibility of trans athletes. We accept, rightly, that people get to choose their own gender ID, and we don’t police that designation based on whether they have or haven’t had various medical interventions like hormone-replacement therapy. Is this standard going to complicate the discussion about sex differences in athletes, especially when it comes to male-to-female trans athletes?

Yes, it is going to complicate it. But working with the Canadian Centre for Ethics in Sport, I came to the conclusion that we just have to live with that if we are going to claim we are dividing by gender.

Live with it how?

If we are going to say that people get to be divided by gender, and we take gender seriously, then we let people play according to their gender, not according to biological haves or have-nots. You have to understand I don’t really care about sports, so I’m comfortable with that. I get that a lot of people are not comfortable with it.

So in the end — as a non-sports fan, at least — you’re comfortable with individual athlete’s gender ID, and nothing else, determining which group they compete in?

Yes. In this way, I agree with all the same facts as Epstein, with whom I’ve somewhat collaborated on beating back at stupid “feminist” claims about testosterone not mattering — but I think he and I end up in different places on the question of whether gender identification is adequate for deciding who gets to play as a woman or a man.

Part of the problem here, of course, is that, in many ways, male and female athletes are still treated differently. They aren’t truly treated as equivalent categories, right?

There’s a whole bullshit level going on with regard to doping. Basically, athletes who identify as men can get TUEs (Therapeutic-Use Exemptions) to get extra testosterone for “medical purposes.” I suspect Lance Armstrong got himself one after testicular cancer, for example. (Although I don’t know if he’s governed by the World Anti-Doping Agency.) I don’t think a woman could ever get such an exemption. It’s seen as a man’s hormone.

So, for example, one “allowable” condition, WADA told me when I asked a few years back, is Klinefelter syndrome — having XXY chromosomes, which lowers your T production. Such men are typically very tall. So if they can show they have XXY, they’re allowed to dope with extra T. A woman born with low T? She’s not allowed to dope. Even if she can show her T level is well below that of an average woman. It proves they think it is a “man’s” hormone. That’s just stupid, horseshit biology, and very much lacking in a justice understanding, from my point of view. I like my T.

(Update: In my question to Dreger about male-female differences in testosterone levels, I worded things too strongly, and readers might have come away with the idea that Rebecca Jordan-Young and Katrina Karkazis were arguing testosterone hardly matters at all. in fact, the debate between them, Dreger, and Epstein had more to do with how much of the difference between male and female athletic performance could be attributed to testosterone levels. I’ve updated my wording of the question to more accurately capture the debate between the two sides.)