What If We've Been Wrong About Human Sexuality? On Sex at Dawn

Most conversations about sexuality begin with a set of assumptions so embedded we rarely notice them. That jealousy is hardwired. That men are naturally promiscuous and women naturally selective. That monogamy is either our nature or our burden, depending on who you ask.

Christopher Ryan and Cacilda Jethá set out to question all of it in Sex at Dawn: How We Mate, Why We Stray, and What It Means for Modern Relationships (Harper, 2010).

The argument

Their central claim is archaeological and anthropological: human beings did not evolve as pair-bonded, sexually possessive creatures. Drawing on primate research, hunter-gatherer studies, and cross-cultural data, Ryan and Jethá argue that the sexual norms we take for granted — monogamy, jealousy as a sign of love, the idea that straying is a betrayal of our nature — are products of agricultural civilization and the property norms that came with it, not the deep evolutionary inheritance we imagine them to be.

The book makes a direct comparison to our closest primate relatives. Chimpanzees and bonobos share roughly 98% of our DNA. Chimpanzees are hierarchical and competitive. Bonobos use sexuality as social glue — to defuse tension, build bonds, and maintain connection within groups. Ryan and Jethá argue that pre-agricultural human sexuality probably looked more like the latter than we're comfortable admitting.

This is a genuinely provocative argument. It's also controversial among evolutionary biologists and anthropologists. The book has been criticized for selectively deploying evidence and oversimplifying the fossil and ethnographic record. It is best read as a challenge to unexamined assumptions rather than as settled science.

Why it matters anyway

Whatever its limitations as evolutionary history, Sex at Dawn performs a useful function: it surfaces the assumptions most of us carry about what's natural, normal, and inevitable in human sexuality — and holds them up for inspection.

The question "is monogamy natural?" is less interesting than the question it opens: where do my assumptions about sexual desire come from, and do I actually believe them, or have I simply inherited them?

That is a question about erotic identity. And it's one most people never ask with any seriousness.

Ryan and Jethá aren't arguing that everyone should abandon monogamy. They're arguing that we should stop using "human nature" as a conversation-stopper when the actual picture is far more complex, contested, and interesting.

The invitation

The most useful thing Sex at Dawn can do for a reader is create some distance between themselves and the sexual scripts they've absorbed. Not to reject those scripts — but to choose them (or not) with more awareness of where they came from.

What do you actually believe about desire? About fidelity? About what a sexual life is supposed to look like? Not what you've been told. What you actually believe, after looking at the evidence of your own experience.

Those are the questions Sex at Dawn is useful for opening, even if it can't definitively close them.

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Domain 1 of the EROS-Q — Erotic Meaning & Identity — explores the beliefs that shape your sexual life. Some were chosen. Many weren't. Request early access →