Researchers of human behaviour have identified an "orgasm gap": Men usually orgasm during intercourse, whereas women often do not. This book addresses this mystery. The two leading explanations are either that women are "psychologically broken" – Freud’s theory – or badly designed – the "by-product theory." However, there is a much more compelling third explanation. Evolutionary biology, anatomy, physiology, and direct sex research suggest women have evolved under their own selection pressures and orgasm is a fitness-increasing consequence of such selective factors. This is revealed in their patterns of orgasmic response, which are neither random nor inexplicable.Key Features Synthesizes decades of peer-reviewed sex research in anatomy, biology, physiology, and behavior Engagingly written based on feedback from students, peers, and interested lay persons Makes sense of the "orgasm gap" between men and women Provides a wider context of human sexual dimorphism and mutual sexual selection Balances sex research and real-world research and practical applications.