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Why Is Sex Fun? The Evolution of Human Sexuality
Jared Diamond explains why human sexuality—concealed ovulation, recreational sex, female menopause, private sex, exclusively female lactation, and male roles—is bizarre by animal standards, and how these traits evolved through natural selection acting on the conflicting reproductive interests of women and men.
A profile of this book is on the way.
What it’s about
Most of us assume our sexual habits are 'natural,' but Jared Diamond shows that by the standards of the 4,300 other mammal species—and even our closest ape relatives—humans are the weird ones. Why do we have sex for fun on days when conception is impossible? Why do women hide their ovulation even from themselves? Why do women undergo menopause while men stay fertile? Why don't men lactate even though they physiologically could? Drawing on evolutionary biology, primatology, anthropology, and comparative studies, Diamond reveals that each of these puzzles is solved by asking how a trait helped ancestors transmit their genes—and how it emerged from the built-in conflict between the differing reproductive strategies of the two sexes. Provocative, witty, and rigorous, this book argues that our strange sexuality was as essential to becoming human as our big brains and upright posture.
The through-line
- Who it’s for
- A curious reader who wants to understand why human sexuality and relationships work—and feel—the way they do.
- The problem
- Human sexual behaviors like concealed ovulation, recreational sex, menopause, and unequal parental roles seem natural but are actually deeply puzzling and unexplained. The reader feels confused, sometimes distressed, by the built-in conflicts and self-destructive urges of sex, marriage, and parenting.
- The plan
- Distance yourself from your species-ist, human-centric view of what is 'normal' sexuality.
- Learn how natural selection and the battle of the sexes shape reproductive strategies.
- Examine each human sexual peculiarity—lactation, recreational sex, men's roles, menopause, body signals—as an evolutionary puzzle.
- Apply evolutionary and comparative reasoning to see how each trait helped ancestors transmit genes.
- Use that understanding to gain distance from your instincts and interpret your own and your partner's behavior more wisely.
- The payoff
- The reader understands why their body and desires feel the way they do. · The reader interprets a partner's behavior with more insight and less bewilderment. · The reader gains intellectual distance from instinct-driven, self-destructive sexual behavior.
See our guide
Additional reading
- The Evolution of Human Sexuality · Donald Symons
A foundational text applying evolutionary theory to human sexual behavior, covering many of the core themes discussed in Diamond's book.
- Primate Societies · Barbara B. Smuts et al. (eds.)
A comprehensive reference on the social behavior and mating systems of primates, providing the raw data for the comparative method used throughout the book.
- The Ant and the Peacock: Altruism and Sexual Selection from Darwin to Today · Helena Cronin
A detailed history and explanation of the theory of sexual selection, which underlies the discussion of body signals in Chapter 7.
- Sex, Evolution, and Behavior · Martin Daly and Margo Wilson
An accessible textbook on evolutionary psychology that covers the logic of sexual strategies and parental investment.