From Caster Semenya to Martina Navratilova: the best books on sporting outliers

Sports writer Alex Hutchinson picks the best books that explore sex, gender and the nature-nurture debate The essential goal of sport, according to the bioethicist Thomas Murray, is the "virtuous perfection of our natural talents". But what counts as "natural" - and who decides? These questions swirl beneath the surface of Caster Semenya's unsuccessful challenge to track and field's gender rules. If the answers seem simple and obvious, you probably haven't read science journalist David Epstein's...