“Before the war on drugs, the war on terror, or the war on cancer, there was the war on female sexual desire. It’s a war that has been raging far longer than any other, and its victims number well into the billions by now.”
Are we really designed for monogamy? Like, truly, at a biological level — is lifelong pair-bonding actually what humans evolved to do?
That’s the central question of Sex at Dawn by Christopher Ryan and Cacilda Jethá, and the answer they give is a resounding NO. And honestly? After reading this book, I think they make a compelling case.
Now before you freak out — this isn’t a book about cheating on your partner. It’s a book about understanding what we ARE as a species, so we can stop beating ourselves up for feelings and impulses that are completely natural.
The Standard Narrative Is Wrong
Here’s the story we’ve all been told. Man meets woman. Man provides food and protection. Woman provides exclusivity and offspring. They pair-bond for life because it’s the “natural” thing to do. Every evolutionary psychology textbook, every romantic comedy, every religious sermon — they all reinforce this idea.
Ryan and Jethá call this the “standard narrative,” and they spend the entire book tearing it apart.
Their argument? For the vast majority of human history — we’re talking HUNDREDS OF THOUSANDS of years — our ancestors lived in small, egalitarian bands where food, childcare, and yes, sexual partners were shared. Monogamy as we know it didn’t show up until agriculture, property, and inheritance entered the picture roughly 10,000 years ago.
That’s a blink of an eye in evolutionary terms.
Our Closest Relatives Tell the Story
One of the most fascinating parts of the book is the comparison between humans, chimps, and bonobos. We share roughly 98% of our DNA with both species, but their social and sexual behaviors are wildly different.
Chimps are aggressive and male-dominated. Bonobos? They resolve conflict through sex. Literally. Tension in the group? Sex. Found a new food source? Celebratory sex. Two strangers meet? You guessed it.
Ryan and Jethá argue that our anatomy and social instincts align far more closely with the bonobo model. The evidence — from the shape of human genitalia to the female capacity for multiple orgasms — all points toward a species that evolved for MULTIPLE mating partners, not exclusive pair-bonds.
Uncomfortable to read at first. But the data is hard to argue with.
Agriculture Changed Everything
This was the part that really clicked for me. Before agriculture, there was no concept of “mine.” No land ownership. No inheritance. No reason to control who a woman slept with, because paternity didn’t matter when the whole group raised every child together.
Then we started farming. Suddenly there was surplus. Surplus meant property. Property meant inheritance. And inheritance meant you NEEDED to know which kids were yours. That’s when everything changed — female sexuality became something to be controlled, monitored, and punished.
The authors connect this directly to the rise of patriarchy, sexual shame, and the obsession with virginity that persists in many cultures today. Ten thousand years of cultural programming built on top of millions of years of biology that says something completely different.
No wonder we’re all so confused.
Jealousy Is Cultural, Not Hardwired
This was a big one for me. We assume jealousy is this primal, unstoppable force — “of COURSE you’d be jealous, it’s natural!” But Ryan and Jethá present evidence from dozens of indigenous societies around the world where sexual jealousy barely exists or is considered a character flaw rather than a virtue.
Think about that for a second. Entire cultures where possessiveness over a partner’s body is seen the same way we’d see someone freaking out because their friend had dinner with someone else.
The authors aren’t saying jealousy isn’t real. They’re saying it’s largely LEARNED, reinforced by a culture that treats people as property. And once you see that distinction, you can’t unsee it.
The Disconnect We All Feel
Here’s where the book gets personal. Ryan and Jethá argue that the massive rates of divorce, infidelity, porn consumption, and general sexual frustration in modern society aren’t signs that something is wrong with US. They’re signs that something is wrong with the SYSTEM we’ve built around sexuality.
We’ve created a model — lifelong monogamy with a single partner who must fulfill every emotional, sexual, and companionship need — that goes against millions of years of evolutionary wiring. Then we shame people when they inevitably struggle with it.
That doesn’t mean monogamy can’t work. It clearly does for many people. But understanding that it’s a CHOICE rather than an inevitability is genuinely liberating. You’re not broken if you find other people attractive. You’re a human being navigating a system that wasn’t designed with your biology in mind.
Where I Push Back
Look, the book isn’t perfect. Ryan and Jethá sometimes oversimplify. They paint prehistoric life as a bit too utopian — like an endless communal paradise with no conflict, no competition, and unlimited coconuts. Real life was probably messier than that.
They also cherry-pick their examples from indigenous cultures that support their thesis while glossing over ones that don’t. It’s convincing in the moment, but if you read critically, you’ll notice the gaps.
And the book doesn’t offer much in terms of practical advice. Great, so we’re not wired for monogamy — now what? Ryan and Jethá leave that question mostly unanswered, which can feel frustrating after 300 pages of arguments about why the current system doesn’t work.
Final Thoughts
Sex at Dawn is one of those books that genuinely shifts your perspective. Whether you agree with every claim or not, it forces you to question assumptions about relationships, jealousy, and human sexuality that most of us have never even examined.
It’s well-written, engaging, and occasionally hilarious. Ryan has a sharp wit, and the book moves fast despite being packed with anthropological and biological evidence.
If you’re interested in evolutionary psychology, human sexuality, or just understanding why modern relationships feel so damn complicated — pick this one up. It won’t give you all the answers, but it’ll give you MUCH better questions.
4/5 — highly recommended for anyone curious about the evolutionary roots of human behavior.
Thanks for reading.
— Leonidas
