What can we learn about men and women from people who have lived as both? It’s a fascinating question, and it produces answers that are more than just anecdotal. After all, if a woman transitions to a man and finds that at last he’s taken seriously, promoted faster and paid more, it can’t be because he suddenly has a higher IQ or is better at his job. And if a man who becomes a woman finds that she’s no longer valued at work and can’t get a word in edgeways at meetings, it can’t be her ability or CV that’s to blame.

When Joan Roughgarden was a middle-aged professor of biology at Stanford University in California in 1998, and decided to change her name from