"Sex at Dawn" by Christopher Ryan challenges the traditional understanding of human sexuality and monogamy. Drawing on anthropology, evolutionary psychology, and scientific research, the book argues that humans are not naturally monogamous, and that our ideas about sex and relationships are shaped by culture rather than biology.

The book explores the sexual practices of our primate ancestors and prehistoric human societies to show that humans have a strong propensity for non-monogamous behaviors. Ryan and his co-author Cacilda Jethá discuss the mating habits of bonobos, our closest relatives, who engage in frequent sexual activities with multiple partners as a means to strengthen social bonds.

Furthermore, the authors contend that sexual jealousy and possessiveness are culturally conditioned responses rather than innate emotions. They argue that our sexual nature is more in line with what they call "serial monogamy," where individuals form long-term pair bonds but occasionally engage in casual sexual encounters.

Throughout the book, Ryan and Jethá challenge societal norms around fidelity, infidelity, and the inherent nature of monogamy. They argue that the prevalence of extramarital affairs and divorce rates are indications of the misalignment between our sexual desires and societal expectations.

"Sex at Dawn" urges readers to reevaluate their assumptions about human sexuality and relationships, encouraging a more open and honest discussion about our sexual needs and desires. By examining our evolutionary past and looking critically at our current societal norms, the book aims to offer a fresh perspective on human sexuality and challenge the prevailing narrative surrounding monogamy.