This case explores the question of whether gender identity is determined strictly by genetics (nature) or social variables (nurture).  It is based on a true story about a man who was raised as a girl and later rejected the female gender identity.  The case is designed to help students think scientifically about sex and gender and introduce them to the concept of sexual differentiation. Although developed for an undergraduate course in human anatomy and physiology as an introduction to discussions of the reproductive system, it could be used in a general biology course as a way of giving students practice with critical analysis and making predictions based on theories as well as in a developmental biology course as a way to apply information from animal models to human sex and sexuality.