Professional running is usually a pretty esoteric world. Occasionally, however, a story pops up that also speaks to those who’ve never heard of LetsRun.com. The controversy surrounding hyperandrogenism—the condition in which a woman’s body produces atypically high levels of testosterone—in women’s track and field is one such story.

Crudely stated, the central question is whether it’s ultimately more fair to allow all female runners to compete against each other, regardless of their natural testosterone levels, or whether there should be an upper limit on testosterone—effectively forcing hyperandrogenic women to artificially reduce their levels if they wish to take part in the women’s division. Among other factors, the debate hinges on the following questions: If elite athletes in every sport can be said to benefit from some form of genetic advantage, why should naturally high testosterone levels be any different? And, crucially, who gets to arbitrate such matters?

Unfortunately, discussion on hyperandrogenism tends to devolve on social media. The following is not going to put an end to the mean-spiritedness the topic seems to inspire, but it’s an attempt to articulate some of the key arguments from both sides of the issue.

The Context of the Controversy

“Sex verification” of female athletes has a long and ignominious history that extends back through much of the 20th century. Chromosomal testing (itself an inconclusive method, since a woman can, for instance, be born with a Y chromosome and be “androgen insensitive,” lacking the ability to process testosterone) was implemented by the International Olympic Committee in 1968 and was preceded by invasive gynecological inspections. In other words, there’s a legacy here—and it’s not pretty.

At the center of the current dispute is South African middle-distance runner Caster Semenya. This is understandably not a position Semenya wants to be in, and she has been made to suffer largely because of her competitive success. When Semenya was 18, she won the gold medal in the 800 meters at the 2009 International Association of Athletics Federations (IAAF) World Championships. Her winning time of 1:55.45 was more than eight seconds faster than her best time from the previous year—an astounding progression by the standards of elite-level athletics. This meteoric improvement (and, most likely, Caster’s distinctly muscled physique) then prompted the IAAF to request that Semenya undergo a sex-verification test, which allegedly revealed that she had three times the amount testosterone typically expected in female athletes. (In a massive instance of indiscretion by the IAAF, news about the test broke while the world championships were still in progress.)

As a consequence, in 2011 the IAAF implemented eligibility rules affecting females with hyperandrogenism, using the rationale that higher levels of androgenic hormones is the most significant biological athletic advantage men have over women. Per the new rule, a woman was eligible for competition provided that she had “androgen levels below the male range” which the IAAF set at 10 nanomoles per liter of blood (nmol/L). As a justification for this limit, the organization cited a study that found that 99 percent of elite female athletes had androgen levels below 3.08 nmol/L; setting the threshold at 10 nmol/L was meant to include outliers, such as women with polycystic ovary syndrome (PCOS), and essentially ensure that only hyperandrogenic women (or women who were doping) fell outside the acceptable range.

In 2015, however, Indian sprinter Dutee Chand successfully challenged the hyperandrogenism rule through the Court of Arbitration for Sport (CAS) on the grounds that the IAAF needed more evidence proving the relationship between athletic performance and androgen levels. The rule has been suspended since that time, and the CAS gave the IAAF two years to bolster its case. That deadline falls at the end of this month, at which point the IAAF is expected to submit its evidence to have the hyperandrogenism rule reinstated.

“This Should Never Have Been an Issue of Men vs. Women”

On July 3, the first (and so far only) major piece of that evidence was released. The IAAF announced that it would be bolstering its case with a study published in the British Journal of Sports Medicine in which researchers took blood samples from 2,127 elite track and field athletes (male and female) at the 2011 and 2013 IAAF World Championships. After comparing androgen levels with competition results, the study found that women with high testosterone had an advantage ranging from 1.8 to 4.5 percent, while no such advantage was found in males with higher testosterone. One of the co-authors of the study, Dr. Stéphane Bermon, was quoted in an IAAF press release: “If, as the study shows, in certain events female athletes with higher testosterone levels can have a competitive advantage of between 1.8-4.5% over female athletes with lower testosterone levels, imagine the magnitude of the advantage for female athletes with testosterone levels in the normal male range.”

At what point does a competitive advantage become significant enough that it becomes unfair?

In a detailed dissection of the British Journal of Sports Medicine study, sports scientist Ross Tucker, who regards the hyperandrogenism rule as “the best solution to an impossible problem,” argued that the 1.8 to 4.5 percent range was well short of the benchmark that CAS had set in the Dutee Chand vs. IAAF case. Zeroing in on the language of that decision, Tucker notes that CAS appeared to require that the IAAF prove that female athletes with male levels of testosterone had an advantage “of commensurate significance to the competitive advantage that male athletes enjoy over female athletes.” That advantage, according CAS, would be somewhere between 10 and 12 percent—significantly more than what the recent study found that high-T women had over their peers. For that reason, Tucker thinks it’s unlikely that the IAAF will able to reinstate the hyperandrogenism rule unless it has further, heretofore undisclosed, evidence.

The problem, in Tucker’s view, is that the 10 to 12 percent benchmark was always too high.

“This should never have been an issue of men vs. women,” Tucker writes. “Rather, it should be about whether women who possess a Y-chromosome, and who produce T in the male range, have an unnaturally large advantage over women who do not have those male-level T values.”

Elite Athletes Are “Not Normal”

But aren’t all professional athletes the beneficiaries of some “unnaturally large advantage”?

The CAS case explicitly addresses the issue when it states:

“The Hyperandrogenism Regulations are based on an implicit assumption that hyperandrogenic females enjoy a significant performance advantage over their non-hyperandrogenic peers, which outranks the influence of any other single genetic or biological factor, and which is of comparable significance (if not identical magnitude) to the performance advantage that males typically enjoy over females.”

Definitively proving that high testosterone outranks all other biological advantages is hard to do. For those who believe that the hyperandrogenism rule is morally indefensible, this is part of an essential counterargument.

“Why seek out—or at least wilfully ignore—biological variations that confer advantage across a wide range of skills while penalizing women for more testosterone? Why single out hyperandrogenism as the only variation that confers an unfair advantage in sport?” writes Silvia Camporesi, a runner and professor at King’s College London who specializes in bioethics. Citing the examples of Michael Phelps and Simone Biles, among others, Camporesi points out that all elite athletes are essentially genetic outliers. In her view, it’s arbitrary to impose a ban on hyperandrogenic women.

One counterargument to the counterargument is that Phelps and Biles typically compete against other elite athletes who have similar biological advantages. This is not the case when it comes to Caster Semenya. According to some advocates of the hyperandrogenism rule, the degree of Semenya’s advantage is significant enough that to disregard it would be to disregard the very reason we have separate men’s and women’s categories in the first place.

Here’s Tucker, again:

The argument of “it’s a normal genetic advantage” remains. This argument has frustrated me from the very beginning of the debate, because qualitatively, a woman with a Y chromosome and high T levels is clearly not the same thing as a Jamaican sprinter with fast twitch muscle fibers, or an NBA player who is 208cm tall. Why? Because we have recognized that men and women are different, and created separate categories for them to compete in. We have NOT created categories for height in basketball, for fiber type in running, for foot size or arm length in swimming. We have female category for a reason, and it’s to protect the integrity of the sport and women’s competition against the most powerful genetic influence known to performance—the male chromosome.

Who Makes the Rules?

Contributing to the dilemma, no doubt, is that the “we” cited in the passage above has been predominantly male, if one looks at the histories of organizations like the IOC and the IAAF. Lofty ideals of “protecting the female category” are going to be viewed with suspicion when that “protection” used to entail forcing women to reveal their anatomy.

A parallel criticism is that the hyperandrogenism rule is less about promoting fairness in sport than about perpetuating a prescribed standard of femininity. Part of the argument here is that if Semenya, who was described in a 2009 New Yorker article as “breathtakingly butch,” looked more conventionally feminine by agreeing to “perform gender,” her case might have gone unnoticed. Advocates of this view include Camporesi and Katrina Karkazis, a bioethicist at Stanford University.

“It is also clear the increased scrutiny is reserved for women perceived as not feminine enough, which is the bedrock of what is in the [hyperandrogenism] policies,” Karkazis wrote in the Guardian after Semenya was snubbed by some of her fellow 800-meter runners when she won the gold medal at last summer’s Olympics.

As Karkazis notes in her article, the racial subtext to the hyperandrogenism rule also shouldn’t be ignored. Dutee Chand and Caster Semenya hail from countries—India and South Africa, respectively—with ugly histories of colonial subjugation. When Caster Semenya was born, in early 1991, South Africa was still in the process of dismantling apartheid; universal suffrage was still three years away. Against this backdrop, it’s easy to see why South Africans would be wary when a European-based organization like the IAAF wants to tell one of its athletes that she can’t compete because she doesn’t fit into its preset category of “female athlete.” (For more context here, Ariel Levy’s extensive 2009 profile of Caster Semenya is essential reading.)

Sports Are (Not) Life

The debates about hyperandrogenism are sure to continue, regardless of what CAS decides at the end of this month. The heart of the matter is the extent to which we are willing to accept different standards when deciding who gets to participate in women’s sports than we might for other places where sex-based categories exist. At a time when discrimination—and, more pointedly, discrimination against women—remains a persistent problem in, for example, the workplace or the outdoor industry, making the argument that certain women should be excluded from athletic competition in the name of fairness is going to be contentious, to say the least.

For the New Yorker’s Malcolm Gladwell, another person who falls in the pro-hyperandrogenism rule camp, it comes down to a belief that athletic competitions should, to some extent, be insulated from broader debates about gender politics.

“This is an argument that makes me—and most people—profoundly uncomfortable, because in all other walks of life we do not draw these kinds of hard lines,” Gladwell said in a discussion last year. “But the Olympics is not life!”

It’s certainly nice to think so.