Hurdling over sex? Sport, science, and equity.

Between 1968 and 1999, the International Olympic Committee (IOC) required all female athletes to undergo genetic testing as part of its sex verification policy, under the assumption that it needed to prevent men from impersonating women and competing in female-only events. After critics convinced officials that genetic testing was scientifically and ethically flawed for this purpose, the IOC replaced the policy in 1999 with a system allowing for medical evaluations of an athlete's sex only in cases of "reasonable suspicion," but this system also created injustice for athletes and stoked international controversies. In 2011, the IOC adopted a new policy on female hyperandrogenism, which established an upper hormonal limit for athletes eligible to compete in women's sporting events.

The riddle of sex: biological theories of sexual difference in the early twentieth-century.

At the turn of the twentieth century, biologists such as Oscar Riddle, Thomas Hunt Morgan, Frank Lillie, and Richard Goldschmidt all puzzled over the question of sexual difference, the distinction between male and female. They all offered competing explanations for the biological cause of this difference, and engaged in a fierce debate over the primacy of their respective theories. Riddle propounded a metabolic theory of sex dating from the late-nineteenth century suggesting that metabolism lay at the heart of sexual difference.