Summary

Sex at Dawn explores the fascinating and controversial idea that human beings are not naturally monogamous. Authors Christopher Ryan and Cacilda Jethá challenge the traditional narrative of human sexual evolution, arguing that for most of our existence, humans lived in small, egalitarian groups where sexual relationships were fluid and non-exclusive. They call this the "standard narrative" and present an alternate model, suggesting that humans, like our closest primate relatives, chimps and bonobos, evolved to be sexually promiscuous, with sex serving as a social bonding mechanism and a way to reduce conflict within groups. The book delves into various aspects of human sexuality, examining anatomical evidence, social behaviors in different cultures, and the impact of agriculture on human relationships.

Ryan and Jethá question the conventional belief that male parental investment is the cornerstone of human family structures. They cite numerous examples of societies with partible paternity, where a child is believed to have multiple fathers, showing that paternity certainty may not be as crucial to human nature as some evolutionary psychologists claim. They also discuss the role of mothers and alloparenting, challenging the assumption that the nuclear family is the only natural human family structure. They point to evidence suggesting that prehistoric human life was characterized by communal child care, with mothers receiving help from others in raising their children.

A major theme in the book is the impact of agriculture on human relationships and sexuality. The authors argue that the shift to settled agriculture about ten thousand years ago brought about significant changes in social structures, leading to the rise of private property, political hierarchies, and a decline in the status of women. They contend that these changes also had a profound impact on human sexuality, shifting from a more relaxed and casual approach to a more possessive and restrictive one.

Ryan and Jethá also discuss the complexities of male and female sexuality, exploring topics such as female copulatory vocalization, the Coolidge effect, and the differences in erotic plasticity between men and women. They argue that women's sexuality is often more fluid and contextual than men's, challenging the stereotype of the coy female. The book also delves into the sensitive topic of paraphilias, suggesting that these behaviors may be more prevalent in men due to differences in erotic plasticity.

Throughout the book, Ryan and Jethá challenge conventional views on marriage, monogamy, and jealousy, arguing that these concepts are not as universal as often assumed. They discuss various forms of marriage and sexual relationships found in different cultures, highlighting the diversity of human sexual behavior. The book concludes with a call for a more open and honest approach to human sexuality, urging readers to confront the sky together and find alternative relationship models that fit our evolved nature.