If reproduction is the engine that drives evolution, why engage in non-conceptive sex? In his attempt to tackle this question, Paul Vasey employs concurrent cross-species and cross-cultural perspectives. For the past decade he has conducted research on the development and evolution of female homosexual behavior in free-ranging Japanese macaques at Arashiyama, Japan. He also studies the development and evolution male same-sex sexual attraction in humans at fieldsites in Samoa, Japan and Canada. Since 2003, he has worked in Samoa with members of the fa’afafine community—biological males who live “in the manner of a woman.” Dr. Vasey is a member of the Editorial Board of the Archives of Sexual Behavior. His work has also been the subject of various documentaries on television (National Geographic’s Ultimate Explorer, Discovery Channel) and the radio (U.S National Public Radio, Canadian Broadcasting Corporation, Radio Netherlands).