Cacilda Jethá has an Asian face, a European mind, and an African soul. Born into an Indian family in Mozambique, she fled civil war to Portugal as a child. After studying medicine in Lisbon, she returned to Mozambique in the 1980s where she was the only physician in a vast rural district. She conducted research for the W.H.O. on the sexual behavior of rural Africans to develop more effective AIDS-prevention efforts.

Before meeting Cacilda and co-authoring the New York Times bestseller, Sex at Dawn: The Prehistoric Origins of Modern Sexuality, Christopher Ryan spent most of his life doing odd things in unexpected places—among them, gutting salmon in Alaska, teaching English to prostitutes in Bangkok and self-defense to land-reform activists in Chiapas, Mexico. After completing a PhD in psychology in 2003, Christopher began writing about universal human concerns from a multi-cultural perspective. His work appears in major media all over the world. He speaks to international audiences about human sexuality, prehistoric life, and the counter-intuitive disadvantages of civilization.