These complexities hold in track and field events, too. Even the International Association of Athletics Federations’ own analysis of testosterone and performance, involving more than 1,100 women competing in track and field events, shows that for three of the 11 running events, women with lower testosterone actually did better than those with higher levels.

In other words, for most sports, testosterone levels do not correlate with superior performance. And yet even in the face of overwhelming evidence, the myths are so deeply ingrained in our assumptions about gender and athletics that the highest governing body in sports believes otherwise.

The obvious result is discrimination against female athletes such as Semenya who have naturally high levels of testosterone. But the harm doesn’t stop there.

The athletics association insists that Semenya can still compete, as long as she undergoes medically unnecessary interventions to lower her testosterone level. (Because the testosterone rules have not yet gone into effect, she was able to run — and win — the women’s 800-meter race at a meet in Doha on Friday.) The association underplays the risk of such measures, saying women with high testosterone can lower their levels dramatically by taking an oral contraceptive.

But hormonal contraceptives are often not enough to get testosterone down to the arbitrary permissible level. This means athletes must take stronger drugs, and endure chronic, significant side effects.

The Court of Arbitration for Sport expressed concern about these side effects, saying they could make compliance a “practical impossibility” for athletes. In fact, for that reason the court said its decision was provisional, and that the harms would need to be tracked.

Nevertheless, the International Association of Athletics Federations president, Seb Coe, gave reason for worry when asked whether he would delay the regulations for the 1,500-meter and the mile races — regulated events for which the court said there was no evidence of a difference in performance among athletes with different testosterone levels. Showing a blatant disregard for caution, Coe simply replied, “No,” leaving us to wonder who will monitor the degree of harm, and how will problems be reported and recorded as they arise. How much harm will be acceptable to the court before it reconsiders its position?