First time accepted submitter erdos-bacon sandwich writes "Gender tests may be the most controversial obstacle the athletes face. The London Games tries a new approach based on testosterone. Of all the obstacles athletes have had to overcome to compete in the Olympics, perhaps the most controversial has been the gender test. Originally designed to prevent men from competing in women's events, it is based on the premise that competitors can be sorted into two categories via established scientific rules. But the biological boundaries of gender aren't always clear."