SCIENCE, SPORT, SEX, and the Case of Caster Semenya

In April 2018, the top international governing body for the sport of track and field-the International Association of Athletics Federations (IAAF)-released regulations aimed at limiting the participation of some female athletes competing at the international level in middle-distance running events. The Eligibility Regulations for Female Classification specifically target women with certain differences of sex development (DSDs) and with naturally occurring testosterone levels that exceed those of most other female athletes. To be eligible to compete, such female athletes must lower their testosterone with medication or surgery. This IAAF mandate, which requires unproven medical interventions in otherwise healthy individuals, has prompted considerable debate. Biological sex is far more complicated than junior high school biology might suggest. Although most men have 46 XY chromosomes and most women have 46 XX chromosomes, biological science today recognizes that there are also 46 XX males and 46 XY females. The IAAF regulations apply only to female athletes with 46 XY sex chromosomes with certain DSDs and who compete in women's running events of distances between 400 meters and one mile. The approach taken by the IAAF to developing its latest version of female eligibility regulation is contorted and confusing. Earlier regulations released in 2011 focused on all women with high testosterone. These rules were suspended by the Court of Arbitration for Sport (CAS) in 2015, following a challenge by the Indian sprinter Dutee Chand, due to a lack of evidence on the relationship between naturally occurring testosterone and in-competition performance.