These ‘half-siders’ offer a unique opportunity to test the authority of gonadal sex hormones in shaping brains and behaviour. Gynandromorphs may be made up of two sexes, but they share just one bloodstream, which means they’re bathed in the same hormonal milieu. Is the solitary testis and its brawny androgens the supreme driver of sexual fate for the chimera’s entire brain, as the Organizational Concept predicts, or could the ‘passive’ feminine side somehow prevail?
