Track and field history was made in Zagreb on Tuesday night as Francine Niyonsaba became the first athlete who has identified herself as having a difference of sex development (DSD) to officially break a world record. The Burundian did it in style, shattering the old 2,000m best by more than two seconds as she crossed the line in 5:21.26. While the 2,000m is not run frequently, Niyonsaba’s performance will inevitably reignite the debate over athletes with DSDs, given they are barred from competing internationally between 400m and 1600m unless they take medication to reduce their high testosterone. Niyonsaba, who won the silver medal over 800m at the 2016 Rio Olympics before moving up in distance due to the World Athletics rules, has had an astonishing year – winning the Diamond League title at 5,000m and running the fifth-fastest outdoor 3,000m time ever. But in Croatia she produced the cherry on the cake. Going through halfway in 2:41.37 put Niyonsaba on pace to break the world record of 5:23.75, set indoors by Ethiopia’s Genzebe Dibaba in 2017. The 28-year-old then powered to glory with a final lap of 63 seconds to break the record. While Niyonsaba is a popular athlete, others in the sport including the two-times 400m Olympic champion Shaunae Miller-Uibo have questioned why World Athletics does not extend its rules regarding DSDs to other events. In 2019, the court of arbitration for sport (Cas) ruled that 46 XY DSD athletes “enjoy a significant sporting advantage … over 46 XX athletes without such DSD” due to their biology. Cas added: “Individuals with 5-ARD have what is commonly identified as the male chromosomal sex (XY and not XX), male gonads (testes not ovaries) and levels of circulating testosterone in the male range (7.7-29.4 nmol/L), which are significantly higher than the female range (0.06-1.68 nmol/L).”