The baffle of the sexes
Forget a simple XX or XY - what determines whether it's a boy or a girl is more puzzling than first thought.
By Peter Ellingsen.
In some ways it is the most basic question of all. Are you are a man or a woman? For centuries, it seemed simple. Men had male sex organs; women had female ones. This did not do a lot for hermaphrodites, who were born with both, but science seemed to solve the impasse by coming up with a subatomic rather than surface solution: men had XY chromosomes; women had XX chromosomes.
But in the 1990s, researchers, including Melbourne's Dr Andrew Sinclair, in a study of "intersex" people - those with ambiguous genitalia - unearthed a new gene that blew the old certainty out of the water.