The Olympic stadium was quiet on Wednesday morning, and spectators in the sparsely filled stands seemed to pay little notice to South African runner Caster Semenya as she cruised to an easy win in her first-round heat of the 800 meters. But on Saturday evening, when Semenya will contest the 800-meter final, she’ll have the world’s eyes on her. “There is no more certain gold medal in the Rio Olympics than Semenya,” wrote Ross Tucker, an exercise scientist in South Africa, on his blog, The Science of Sport. “She could trip and fall, anywhere in the first lap, lose 20m, and still win the race.”

If she does indeed dominate, some sports fans will be cheering Semenya, while others will be less inclined to celebrate, believing that she has an unfair advantage over her rivals. Semenya made headlines in 2009 amid rumors that track’s governing body, the International Association of Athletics Federations, had required her to undergo tests to confirm that she was female. Media accounts have reported that she has hyperandrogenism, a condition that causes higher-than-average testosterone levels — an allegation that neither Semenya nor the IAAF has publicly confirmed.

Semenya’s case is the latest saga in sport’s checkered history of sex testing, a task that is purportedly aimed at creating an even playing field but — as I’ve discussed previously — raises serious questions about how athletics organizations treat women. Her muscular build, deep voice and remarkable results had raised suspicions among some of Semenya’s rivals about whether she was really a woman. “Just look at her,” said Mariya Savinova, a Russian runner now tangled in her country’s doping scandal.

Savinova’s comment highlights what’s wrong with making competitors in women’s events prove that they’re women: It encourages people to police who looks “feminine enough” and sanctions discriminatory behavior that can have life-threatening consequences. Indian middle-distance runner Santhi Soundarajan attempted suicide after failing a gender test in 2007 and being shunned by her community.

Even if you think sex testing is necessary to ensure that women’s athletics are fair, the rules would need to be enforced uniformly. Testimony presented at a hearing on the IAAF’s sex testing procedures last year showed that “to date, [the testosterone limit] has only been used against women from developing countries” and that the rules created “an inconsistent and unfair patchwork of compliance by different countries around the world.” It’s notable that the women who’ve made the news for being scrutinized under the testosterone rule have been people of color.

Sport has a long history of humiliating women deemed “too masculine.” To ensure that men were not masquerading as women in order to compete and win at women’s sports, competitors were subjected to sex tests such as nude body inspections and chromosome testing. Eventually officials realized that these tests couldn’t definitively distinguish between male and female competitors, because sex is not a binary trait but exists along a continuum. For instance, people with androgen insensitivity syndrome are born with XY chromosomes but develop female anatomy, because their bodies don’t respond typically to testosterone. Others are born with female genitalia but have male sex anatomy internally. These are just two examples of the wide range of variations found across the spectrum.

After an especially shameful 1980s episode in which Spanish hurdler María José Martínez-Patiño was publicly shunned and outed as having androgen insensitivity syndrome, the blanket tests were dropped, and instead women deemed suspicious could be called in for testing. This is what happened to Semenya. The invasion of privacy and testing she endured created a push for a less ostracizing way to ensure that athletes vying in women’s competitions were women, and in 2011 the IAAF settled on a new approach, which the International Olympic Committee also adopted in 2012.

Rather than allow inspections of women’s bodies, the new rule set an upper limit on testosterone. Women could compete only if their testosterone levels were below 10 nanomoles per liter — a cutoff devised by sampling woman athletes with polycystic ovary syndrome (a condition associated with elevated testosterone levels) and adding five standard deviations to it. Tucker wrote on his blog that this limit is “threefold higher than a level that applies to 99 in 100 women participants.”

The argument for testosterone testing says that we divide sport into men’s and women’s categories because men have a practically unconquerable natural advantage over women. World records for men’s track and field and road running events are an average of 12.6 percent faster than the equivalent women’s events, and we give women their own class, akin to a weight class in combat sports, so they can have a chance to excel.

The argument against testing is that the competitive advantage that men have over women arises from biological factors linked to sex, but sex is a biological trait without hard and fast borders. And that we can pretend that we divide competition by sex, but what we’re really doing is separating athletes by gender, which is an identity that has a social and cultural context as well, and those contexts may confer distinct advantages and disadvantages, too. Under this system, there’s an obligation to recognize Semenya under the gender identity that she has inhabited since birth, and to do so without subjecting her to invasive and humiliating inspections or tests. Her identity should not be up to strangers to decide.

The debate over whether hormone testing is fair doesn’t have a scientific answer, only science-informed ones. There’s pretty good evidence that testosterone, a muscle-building hormone that men typically produce in greater quantities than women, is a performance-enhancing substance — that’s why it’s so popular among dopers. Joanna Harper, an athlete, scientist and transgender woman, found that her running performance dropped within weeks of starting therapy to reduce her testosterone levels, and she has documented similar changes in other male-to-female transgender runners. Insofar as you can pin the male advantage to a single factor, testosterone is it.

Science shows that testosterone gives athletes an advantage, but it can’t tell us how much advantage is too much or how to categorize athletes who are women by gender but also have male sex traits — those are philosophical questions, not scientific ones. But it’s hard not to see sexism in the answers that the IAAF is providing. As espnW columnist Kate Fagan tweeted recently, “I shall steal line from someone on Twitter: I know Semenya is a woman because people are trying to control her body.” Women with high testosterone levels have been pressured to undergo life-changing surgery and medical interventions in exchange for the right to compete.

The IAAF’s testosterone limit is necessarily arbitrary, and when Indian sprinter Dutee Chand faced scrutiny and demands to undergo treatment to reduce her testosterone levels, she pushed back. The medical interventions would be invasive, would be potentially irreversible and would come with side effects that could “interfere with the way my body has worked my whole life,” she wrote in a letter to the secretary general of the Athletics Federation of India, asking to have her eligibility reinstated. “I was born a woman, reared up as a woman, I identify as a woman and I believe I should be allowed to compete with other women, many of whom are either taller than me or come from more privileged backgrounds, things that most certainly give them an edge over me.”

The case ended up in the Court of Arbitration for Sport, which suspended the policy in July 2015 and gave the IAAF two years to return with science to show that women with naturally occurring testosterone over the 10 nmol/L limit have an unfair advantage. The ruling meant that Chand, Semenya and other hyperandrogenic athletes could compete without altering their hormones.

The decision was greeted in some corners of the internet as a sign of the apocalypse — the end of women’s sports as we know it. Hyperandrogenic athletes, this line of reasoning held, were being given a chance to compete in their identified gender at the expense of other women.

You can think of this as a version of the classic trolley car problem in which a runaway trolley car is speeding down the tracks, and a human operator has an opportunity to pull a lever to direct the car down another track — but both options will result in casualties.

When some testing advocates look at this problem, they see that sending the car down the track with no sex or hormone testing will mow down female athletes and women’s sports. Send the trolley down the track with testing, and you tear down Semenya, Chand and other athletes with unusually high testosterone levels.

Stated this way, it seems like a straightforward equation. Someone will get run over, but if you pull the lever in favor of testosterone testing, the only people hurt are the women with naturally high levels. If it’s strictly a numbers game, you’ve found a solution that harms the fewest people.

But that’s not what I see on the tracks. Instead, I see that pulling the lever in favor of testosterone testing sends the trolley down a track that will harm not only women with high testosterone levels, but also every other woman athlete who looks too “manly” or otherwise does not conform to someone else’s notions of what a woman should be. I see the trolley barreling down a track that will crush the culture that I want sport to strive for — one that celebrates women athletes of all shapes, sizes, forms and talents.

Although there’s been a lot of mansplaining about why a testosterone limit is warranted, this isn’t just a black-and-white case of sexism, since woman athletes (including Martinez-Patiño, the Spanish hurdler who was shunned after testing in the 1980s) have also spoken in favor of the rules. Tucker and Harper, high-profile proponents of hormone limits, have carefully acknowledged the cultural and social factors at play, but I don’t think they give these other considerations enough weight. When you’ve had people tell you that your body is too muscular or you’re not feminine enough (as I have), a system that makes it OK to enforce a particular kind of female body feels vindictive.

There are consequences of an institutionalized process that seeks and targets women for looking like men (whatever that means). At the conclusion of a hearing on her case, Chand gave a brief statement telling the panel that “she fears that if she loses her appeal, she will have to leave her village.” This fear isn’t ungrounded. She also recounted the story of a young female friend who’d been forced out of her village after people refused to recognize her as a girl because of her appearance.

It’s easy to sympathize with the women competing with Semenya. Her talents can seem insurmountable. But it’s wrong to prohibit her from competing with the body she was born with. She is not the first woman (or man) to dominate the competition. Once in a while someone comes along who’s an extreme case. Usually, we celebrate this.

At Chand’s Court of Arbitration for Sport hearing, accomplished British runner Paula Radcliffe testified in favor of the hormone limit, saying that the rule fell under similar regulations “designed to ensure success is determined solely by talent and dedication, and not by ‘unfair’ advantage.”

But what is “unfair?” Radcliffe also possesses extraordinary talent, and it’s hard to tease out and compare the boost that different advantages confer. Her marathon world record has remained untouched for more than a decade. Radcliffe herself has faced allegations of doping, abetted by a culture of doping that has made every performance suspect. Sex testing creates a similar atmosphere of suspicion, but the difference is that dopers are deliberately cheating. Hyperandrogenic women are simply competing with the bodies they were born with in the gender with which they identify and belong.

In support of the hormone limit, the IAAF argued that dismissing conditions that produce unusually high levels of testosterone as “naturally occurring advantages would compromise the integrity of sport,” since that would be “analogous to having a system, where weight classifications exist, but then waiving the weight limit for certain individuals who cannot reduce their weight enough to fit into the required category.” The problem with that analogy is that in the case of a weight system, the person too heavy for a particular weight class has another class to compete in. What happens to Semenya under these rules if she doesn’t want to alter her body? The IAAF has said that a woman ineligible under the rules could compete with the men, but that feels a lot like shunning.

Perhaps the most uncomfortable truth that this controversy forces us to confront is that there’s no such thing as a level playing field in sport. As much as we like the idea of athletes winning through hard work, guts and spirit, the fact is, much of it comes down to born talent. Most competitors never had a chance.

In the end, the real question to ask is: What is the purpose of sport? Is it more important to provide uncomplicated stories that make us feel uplifted, or to celebrate extraordinary human effort and performance? My vote goes to the latter. Participating in sports taught me to feel powerful in my body, and I’m glad that no one put limits on how strong I could be. When Semenya takes to the line on Saturday, I’ll be cheering for her every step of the way.

This was an edition of Strength in Numbers, my column exploring the science of sports and athleticism. Got feedback, suggestions or a news tip? Email me, leave suggestions in the comments section or tweet to me @CragCrest.