Since the very beginning of women’s sports, there has been a struggle to define who, exactly, gets to compete in the women’s category. A century later, this struggle is still very much alive. Host Rose Eveleth will explore a question that goes far beyond sports: What is fair and who decides?

Would you alter your body for the chance to compete for a gold medal? That’s the question facing a small group of elite athletes right now. Last year, track and field authorities announced new regulations that mean some athletes can’t compete in the female category unless they lower their body’s naturally occurring testosterone levels. In this episode you’ll meet one of those runners, Christine Mboma, a reigning Olympic silver medalist, and hear about the difficult choice she faces.

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We go back to the beginnings of women’s inclusion in elite sports. It turns out that men had an odd variety of concerns about women athletes. Some doubted these athletes were even women at all. And that skepticism resulted in the first sex testing policies.

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We meet Kenyan sprinter Maximila Imali, who—like Christine—has been sidelined by DSD policies. She makes a different choice from Christine: to fight the regulations in court. And we learn about an earlier fight, when scientists, athletes, and journalists spent thirty years trying to end an earlier version of sex testing.

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In 2009, South African sprinter Caster Semenya won gold at the World Championships. But instead of a celebration, she endured endless speculation about her body, her biology, and her gender. And soon, sports organizations would launch a new round of regulations, lead to multiple court cases, and require sporting organizations to justify their claim that DSD athletes have an unfair advantage.

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A battle over science and ethics unfolds. World Athletics releases and then tweaks multiple policies impacting DSD athletes, while critics cry foul. In this episode, World Athletics doubles down on its claims, Caster Semenya challenges the rules again, and we dig deep on a big question: what constitutes an “unfair” advantage on the track?

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Christine and Max are some of the most recent female athletes in this century-long history to face tests, stigma, and restrictions. But they are unlikely to be the last. In this episode, we find out whether Christine qualifies for the Paris Olympics, as well as the fate of Max’s court case. And we explore the broader implications of the sex binary in sports. Is there a better way for sports to be categorized?