Genitals to genes: the history and biology of gender verification in the Olympics.

From 1968 to 1998, female Olympic athletes were expected to prove their "femininity," ostensibly to stop male "ringers" from passing themselves off as female competitors. Rumours that men were competing in drag had been around since at least the 1936 games. The sex tests started out as simple anatomical examinations--the "nude parade," but rapidly progressed to cellular-based tests (the presence of a Barr body), and eventually to molecular-based tests (the absence of the SRY gene). Women went from being defined by genitalia to cellular characteristics, and finally, by genotype but ironically, as the tests become more sophisticated, both sensitivity and specificity suffered. This paper reviews the science underlying the sex tests, their history, and the controversy that accompanied them.