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Sex at Dawn: How We Mate, Why We Stray, and What It Means for Modern Relationships Paperback – July 5, 2011
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“Sex at Dawn challenges conventional wisdom about sex in a big way. By examining the prehistoric origins of human sexual behavior the authors are able to expose the fallacies and weaknesses of standard theories proposed by most experts. This is a provocative, entertaining, and pioneering book. I learned a lot from it and recommend it highly.” — Andrew Weil, M.D.
“Sex at Dawn irrefutably shows that what is obvious—that human beings, both male and female, are lustful—is true, and has always been so…. The more dubious its evidentiary basis and lack of connection with current reality, the more ardently the scientific inevitability of monogamy is maintained—even as it falls away around us.” — Stanton Peele, Ph.D.
A controversial, idea-driven book that challenges everything you (think you) know about sex, monogamy, marriage, and family. In the words of Steve Taylor (The Fall, Waking From Sleep), Sex at Dawn is “a wonderfully provocative and well-written book which completely re-evaluates human sexual behavior and gets to the root of many of our social and psychological ills.”
- Print length402 pages
- LanguageEnglish
- PublisherHarper Perennial
- Publication dateJuly 5, 2011
- Dimensions8.06 x 5.33 x 1.04 inches
- ISBN-109780061707810
- ISBN-13978-0061707810
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What's it about?
Challenges conventional wisdom about human sexual behavior by examining prehistoric origins, exposing fallacies of standard theories.
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No creature needs to be threatened with death to act in accord with its own nature.2,942 Kindle readers highlighted this
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Because of private property, for the first time in the history of our species, paternity became a crucial concern.2,304 Kindle readers highlighted this
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Monogamy is not found in any social, group-living primate except—if the standard narrative is to be believed—us.2,082 Kindle readers highlighted this
Editorial Reviews
Review
“Sex At Dawn has helped me understand myself and the world so much more clearly.” — Ilana Glazer, co-creator of Broad City
“Sex At Dawn is the single most important book about human sexuality since Alfred Kinsey unleashed Sexual Behavior in the Human Male on the American public in 1948.” — Dan Savage
“Funny, witty, and light ... Sex at Dawn is a scandal in the best sense, one that will have you reading the best parts aloud and reassessing your ideas about humanity’s basic urges well after the book is done.” — Newsweek
“Sex At Dawn challenges conventional wisdom about sex in a big way... This is a provocative, entertaining, and pioneering book. I learned a lot from it and recommend it highly.” — Andrew Weil, M.D., author of Healthy Aging
“Sex At Dawn is a provocative and engaging synthesis... that has the added benefit of being a joy to read.... A book sure to generate discussion, and one likely to produce more than a few difficult conversations with family marriage counselors.” — Eric Michael Johnson, Seed Magazine
“You clearly have an exciting book on your hands, whether people agree with it or not: these are issues that will need debating over and over before we will arrive at a resolution.” — Frans de Waal, author of The Age of Empathy
“A wonderfully provocative and well-written book which completely re-evaluates human sexual behaviour and gets to the root of many of our social and psychological ills.” — Steve Taylor, author of The Fall and Waking From Sleep
“One of the most original books I’ve read in years, Sex at Dawn manages to be both enormously erudite and wildly entertaining―even, frequently, hilarious. . . . A must-read for anyone interested in where our sexual impulses come from.” — Tony Perrottet, author of Napoleon's Privates
“This paradigm-shifting book is a thoroughly original discussion of the origins and nature of human sexuality... These authors have a gift for making complex material reader-friendly, filling each chapter with humor and passion as well as dozens of revolutionary insights.” — Stanley Krippner, Ph.D.
“Christopher Ryan and Cacilda Jetha have written the essential corrective to the evolutionary psychology literature...” — Stanton Peele, Ph.D.
From the Back Cover
In this controversial, thought-provoking, and brilliant book, renegade thinkers Christopher Ryan and Cacilda Jethá debunk almost everything we “know” about sex, weaving together convergent, frequently overlooked evidence from anthropology, archaeology, primatology, anatomy, and psychosexuality to show how far from human nature monogamy really is. In Sex at Dawn, the authors expose the ancient roots of human sexuality while pointing toward a more optimistic future illuminated by our innate capacities for love, cooperation, and generosity.
About the Author
Christopher Ryan, PhD, is a research psychologist. He lives in Barcelona, Spain.
Cacilda Jethá, MD, is a practicing psychiatrist. She lives in Barcelona, Spain.
Product details
- ASIN : 0061707813
- Publisher : Harper Perennial; Reprint edition (July 5, 2011)
- Language : English
- Paperback : 402 pages
- ISBN-10 : 9780061707810
- ISBN-13 : 978-0061707810
- Item Weight : 14.3 ounces
- Dimensions : 8.06 x 5.33 x 1.04 inches
- Best Sellers Rank: #21,268 in Books (See Top 100 in Books)
- #13 in Medical Psychology of Sexuality
- #18 in Psychology & Counseling Books on Sexuality
- #56 in Sex & Sexuality
- Customer Reviews:
About the authors

Discover more of the author’s books, see similar authors, read author blogs and more

Christopher and his work have been featured just about everywhere, including: MSNBC, Fox News, CNN, NPR, The New York Times, Playboy, The Washington Post, Time, Newsweek, The Atlantic, Outside, Salon, Seed, Big Think, and Andrew Sullivan’s Daily Dish.
Chris has been a featured speaker all over the world, from TED in Long Beach, CA to Ciudad de las Ideas in Mexico, to the Festival of Dangerous Ideas at the Sydney Opera House. He's consulted at various hospitals, provided expert testimony in a Canadian constitutional case, and contributed to publications both scholarly and popular.
Even before co-authoring the New York Times best-seller, Sex at Dawn: How We Mate, Why We Stray, and What it Means for Modern Relationships, with partner-in-crime, Cacilda Jethá, MD, he was on a wild ride. After receiving a BA in English and American literature in 1984 he spent several decades traveling around the world, pausing in unexpected places to work at decidedly odd jobs (e.g., gutting salmon in Alaska, teaching English to prostitutes in Bangkok and self-defense to land-reform activists in Mexico, managing commercial real-estate in New York’s Diamond District, helping Spanish physicians publish their research). In his mid-30s, Chris decided to pursue doctoral studies in Psychology.
Drawing upon his multi-cultural experience, Chris' research focused on distinguishing the human from the cultural, first by focusing on shamanism and ethnobotony—studying how various societies interact with novel states of consciousness and sacred plants—and later, by looking at similarly diverse cultural perspectives on sexuality. His doctoral dissertation analyzed the prehistoric roots of human sexuality, and was guided by the world-renowned psychologist, Stanley Krippner, at Saybrook Graduate School, in San Francisco, CA.
More at ChrisRyanPhD.com
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Cacilda Jethá has an Indian face, a European education, and an African soul. She was born in Mozambique to a family that had immigrated two generations earlier from Goa, India. As a child, she fled civil war to Portugal, where she received most of her education and medical training before returning to Mozambique in the late 1980s. A young physician determined to help heal her country, Cacilda spent seven years as the only physician serving some 50,000 people in a vast rural district in the north of the country. While there, Cacilda also conducted research (funded by the World Health Organization) on the sexual behavior of rural Mozambicans in order to help design more effective AIDS prevention efforts.
After almost a decade in Mozambique, Cacilda returned to Portugal, where she completed her medical residency training in both psychiatry (at the prestigious Hospital de Julio de Matos in Lisbon) and occupational medicine.
She and Christopher Ryan currently divide their time between Portland, Oregon and Barcelona, Spain. She speaks Portuguese, French, Spanish, Catalán, English, and some rusty Swahili.
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Learn more how customers reviews work on AmazonCustomers say
Customers find the humor in the book to be appreciated and conversational. They also describe the book as fascinating, playful, and excellent. Readers praise the writing style as extremely well written and approachable. They find the content informative and thought-provoking, offering a fresh perspective on modern relationships. However, some customers feel the plot is repetitive and disappointing with a promising start.
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Customers find the book fascinating, amusing, and helpful. They also say it's refreshing and liberating.
"...It is a fascinating read, which covers a lot of ground and makes some very compelling arguments...." Read more
"...The whole thing is amazing and forces one to reexamine the merit and utility of monogamy, among various other cultural beliefs...." Read more
"...and groups, low levels of chronic stress and high levels of overall satisfaction for most of our ancestors.”..." Read more
"...with every argument in this book, but it's certainly liberating and refreshing to encounter an honest discussion of our favorite subject: Sex...." Read more
Customers find the book extremely interesting and informative. They say it asks serious and compelling questions, presents substantial anthropological, biological, and social data, and provides surprising facts. Readers also say the argument makes a lot of sense.
"...is a fascinating read, which covers a lot of ground and makes some very compelling arguments...." Read more
"...First, the book is extremely well written. Complex subjects are analyzed and explained clearly and concisely, and wonderful examples and metaphors..." Read more
"...But did they convince me? No. They didn’t. They ask serious and compelling questions, such as: “Might the contemporary pandemics of fracturing..." Read more
"Really interesting perspective on human sexuality. It made me realize that we as people aren't "broken" for "failed" past relationships." Read more
Customers find the writing style extremely well written, approachable, and light. They also mention that the author uses a great deal of street language to get the points across in a more interesting and eye-opening way. Customers also say that the book presents interesting and alternative takes that are easy to follow.
"...First, the book is extremely well written...." Read more
"...ideas contained in this highly entertaining and very approachable book...." Read more
"This is an amusing and light read, salted with sarcastic quips and, of course, covering a salacious topic...." Read more
"...We are evolving away from our primordial past. It’s an awkward, dissonant, difficult, fascinating journey...." Read more
Customers appreciate the humor in the book. They also say the author uses humor in a fun way that doesn't sound like he's trying.
"...It's also quite funny in places, which was quite welcome...." Read more
"...The authors also display a delightful sense of humor at various points during exploration of topics most people don't feel comfortable discussing..." Read more
"...Frankly, I’m not sure. I love their playful writing style and applaud their disruptive arguments. But did they convince me? No. They didn’t...." Read more
"This is an amusing and light read, salted with sarcastic quips and, of course, covering a salacious topic...." Read more
Customers find the book's sexual content fine, fantastic, and interesting. They also say it's well-researched and presented, with scientific information and historical narratives.
"...I did have some informative scientific information and historical narratives that I enjoyed learning from...." Read more
"...It's an amazing look at sexuality, relationships, history and makes me really think hard about the path we feel forced to follow when it comes to..." Read more
"Bery thiught povoking and entertaining book. Changed my perspective on monogamy and dicersity of approach to sex. Highly recommended book." Read more
"...It is very informative full of quotes, history and a lot of amusing commentary and snark. Open your mind and read this !" Read more
Customers find the book meticulously presented and researched. They also say it sheds light on the complexities of where we come from. Readers appreciate the author's sense of humor and way of presenting his points. They say the cover looks good.
"...and explained clearly and concisely, and wonderful examples and metaphors are frequently offered to emphasize points...." Read more
"...humanity to embrace and much of the science is valid and sheds light on the complexities of where we come from biologically, which is not strict..." Read more
"...thing about this book is that it is undeniably fair in its thorough description of the opposing viewpoint, often taking several pages to illustrate..." Read more
"...The downside is covered here with wonderful clarity and no easy answers,its an honest book about man's hunter gathering past and our close..." Read more
Customers have mixed opinions about the book's argument quality. Some find it well-argued, while others say it's incoherent and poorly written.
"...I love their playful writing style and applaud their disruptive arguments. But did they convince me? No. They didn’t...." Read more
"...question which the authors argue we are not, but with logic which is not convincing. The most likely answer is, some are and some are not...." Read more
"...This book was a bit of a mixed bag for me. I thought they made some good arguments, but the language often got a little jokey informal trying-to-be-..." Read more
"...Unfortunately, the arguments are completely specious...." Read more
Customers find the plot poorly written, repetitive, and lacking a standard narrative. They also say the thesis is interesting, but the conclusion misses its logic at the end and ends too quickly.
"...The fact is that there is no standard narrative that I know of in the contemporary scientific literature...." Read more
"...– while Sex at Dusk starts very slow, is more academic and relatively more boring...." Read more
"...It’s an awkward, dissonant, difficult, fascinating journey. Growing up always is, even as a species...." Read more
"...case studies, the subsequent material seems sort of of dull and repetitive...." Read more
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Okay, okay, I know what this looks like, but I can explain! Quiet, Chad, let me handle this. I can explain! I'm just - please, stop crying and listen - I'm just fulfilling my evolutionary heritage and helping to cement social bonds with... um... the pizza boy, but that'snotthepoint!! That's not the point! Look, before you do anything, y'know, drastic, you just need to read this book....)
Humans are really good at figuring things out. As far as we go, we have a real knack for taking things apart and figuring out how they work. Though determined curiosity and perseverance, we know what's happening at the center of the sun, we know how the continents slide across the surface of the earth, how plants turn sunlight into potatoes. We can smash atoms and cure disease and peer back to the moment of creation itself. There is almost nothing that humans cannot comprehend if we put our minds to it.
Except ourselves.
Don't get me wrong - we have made great strides in philosophy and psychology, and come very far in understanding human origins and our spread across the planet. But there is a fundamental problem that we have when we study ourselves, and that is that we cannot do so objectively. Try as we might, it is impossible to completely put aside our own biases, judgments and backgrounds when we study how humans behave and try to understand why they do what they do. They are still there, if you look for them, and nowhere are they more evident than in the search for the origins of foundations of human sexuality.
The standard model, as it's often called, goes something like this: ancient men and women established a pattern of monogamy based on mutual self-interest. The man would keep to one mate in order to be absolutely sure that he was dedicating his efforts towards raising his own kids and not someone else's. If a man had multiple partners, he wouldn't be able to provide for them all, and his genetic investment would die out. So, in terms of efficiency, it is much better for the man to keep himself to one woman, focusing all his attention on the children he knows he has fathered and making sure they live to have children of their own.
As far as women are concerned, they require the resources that the men bring. When pregnant, a woman's physical capacities are reduced and she is in a vulnerable state, so by staying monogamous, she is essentially purchasing security and resources that would otherwise be unavailable to her in a world that brought quick and merciless death to the weak. If she slept around, the man wouldn't be sure that the child she bore was his, and would therefore have less interest in taking care of the both of them. Thus, monogamy is the best bet to assure the survival of herself and her child.
This is the story that's been told for a long time, and it's considered by most to be the truth. Christopher Ryan and Cacilda Jetha, however, disagree. Not only do they think the standard model is wrong, but they think it is nothing more than a relic of our own modern biases and hang-ups. The process, they say, can be referred to as "Flintstonization."
As you know, the characters in "The Flintstones" were more or less just like us. They went to work, they had houses and appliances and domestic disputes. They had the same issues and amusements as we did, because we overlaid our own society onto a prehistoric setting. Now in cartoons, that's good entertainment, and in the right hands it can be used as powerful satire and commentary. In science, though, it's just no good.
Starting with Darwin, people have imagined prehistoric humans to have the same sexual values that we have: a demure, reluctant female who is very choosy in deciding which male she will mate with. A bond forms, and they are faithful to each other until the end of their days. Later researchers, looking at our ape cousins, have plenty of observational research to support the idea that very early humans were monogamous. They look at chimps and gorillas and baboons and confirm what they had always suspected - that our natural sexual state is one of monogamy.
The logical conclusion, then, is that our modern attitude towards sexuality, with the rising rates of divorce and teen sexuality, represents a deviation from the way things "should" be, and must therefore be fixed. A loveless marriage, a man's roving eye, a woman who cuckolds her husband, serial monogamists, all of these, according to the standard model, result from our attempts to go against our nature.
Or is it the other way around?
Ryan and Jetha have put together a very compelling argument that the standard model of pre-agricultural human sexuality is not only wrong, but dangerously so. By looking at modern foraging tribes and the way they live, as well as doing a comparative analysis of humans against our nearest ape cousins, they have come to this conclusion: our "natural" sexual state is one of promiscuity. Back in the day, communities were small and tightly bonded, and sex was one of the things that held those bonds tight. Rather than one man and one woman struggling to protect their own genetic line, their entire community made sure that children were cared for and raised well. Everyone was everyone else's responsibility, and in a world of plenty there was no reason to try and enforce any kind of sexual exclusivity.
It was only with the rise of agriculture that it became important to know what was yours, as opposed to someone else's, and that quickly extended from fields and livestock to wives and children. Now that people were keeping their own food and making sure to divide their lands from their neighbor's lands, sharing went out of style. With so much work put into growing crops, that's where the standard model of economic monogamy settled in, and it's been with us ever since. The advent of agriculture changed everything, and not everything for the better.
In addition, the very biology of humans, from the way sperm behaves to the shape of the penis, to the anatomy of the clitoris to the noises women make in the throes of orgasm - all of these point to an evolutionary history of sexual promiscuity. The evidence of our bodies tell us that being locked into a lifetime monogamous pair-bond is not what we evolved to do.
Ryan and Jetha know that their view of the fundamental nature of human sexuality will not be popular, mainly because it completely undermines our vision of who we are. So much law, tradition, education, entertainment and just plain common sense relies on humans being naturally monogamous. It's something that seems so obvious to us that we cannot imagine a society built any other way. Unfortunately, if Ryan and Jetha are right, society is the problem. We have established a cultural norm that goes completely against our biological and evolutionary nature, and which makes people miserable on a daily basis.
I bought this book mainly to stop Dan Savage from nagging me about it. If you listen to Savage's podcast - and you should - you will soon realize that monogamy is something that a lot of people aren't good at. We look at other people with lust in our hearts, we cheat, we stay in relationships where we're sexually miserable just because that's what we "should" do. For most people, our sexual urges are to be fought against, with everything from self-restraint to social shame to law itself. It seems like staying monogamous is one of the hardest things for many people to do.
This, of course, raises the question: if it were natural, would it really be so hard?
It is a fascinating read, which covers a lot of ground and makes some very compelling arguments. It's also quite funny in places, which was quite welcome. In discussing the standard model the authors note that this is, fundamentally, prostitution, wherein the woman uses sex for material resources. This sexual barter system has been assumed to be true for years, leading the authors to write, "Darwin says your mother's a whore. Simple as that." They also put in some special notes for adventurous grad students in the field of sexual research (especially genital to genital rubbing, something popular in bonobo apes, but which is rarely studied in humans) and re-titling the extremely popular song "When A Man Loves a Woman" as "When a Man Becomes Pathologically Obsessed and Sacrifices All Self-Respect and Dignity by Making a Complete Ass of Himself (and Losing the Woman Anyway Because Really, Who Wants a Boyfriend Who Sleeps Out in the Rain Because Someone Told Him To?)"
I don't really know what can be made of the serious information proposed in this book. No matter how it may seem, the authors are not proposing a dissolution of marriage or compulsory orgies or anything like that, nor is this book a "Get Out of Cheating Free" card. We've spent thousands of years putting these restraints on human sexuality, and they're not going to come off anytime soon. The best we can do right now is to be aware of where our ideas about relationships come from, and stop to think about the difference between what is true and what we wish were true. This understanding might help to save relationships that would otherwise work. People cheat not because they're scum or whores, but because they're human. Being monogamous is really hard not because we're weak or flawed, but because it's not what our bodies want for us.
The search for a better understanding of human nature should lead us to being better humans, and nothing should be left out. Not even our most sacred beliefs. Not even sex.
------------------------------------------------
"Asking whether our species is naturally peaceful or warlike, generous or possessive, free-loving or jealous, is like asking whether H2O is naturally a solid, liquid or gas. The only meaningful answer to such a question is: It depends."
- Christopher Ryan and Cacilda Jetha, Sex at Dawn
------------------------------------------------
(Okay? Okay, baby? So you see, I wasn't really cheating - okay, I was, but you can see why, right? I was just acting in accordance with my fundamental humanity, following the biological impulses as determined by millions of years of evolution when we... Hey, where are you going? Where are you? Oh, hell, he's going for the shotgun. Run, Chad, leave your pants, you don't have time, run!)
**SPOILER ALERT** Discussion of the main themes and revelatory points follows.
First, the book is extremely well written. Complex subjects are analyzed and explained clearly and concisely, and wonderful examples and metaphors are frequently offered to emphasize points.
The authors also display a delightful sense of humor at various points during exploration of topics most people don't feel comfortable discussing openly.
The thing that blew me away the most was his discussion of how agriculture changed the world more than any other single event or series of events. With the advent of farming, human societies invented concepts of land ownership and private property. This led to the formation of hierarchical societies, which was necessary to wage war for land and other limited resources--a circumstance that did not exist among hunter-gatherer societies, they say, because no one claimed to own the land or anything else. There simply were no wars for land or resources among prehistoric people; they lived in a world of abundance and would have had no reason to organize to control territory; nor did they store food; they were "immediate return" hunter-gatherers, meaning they consumed what they found or acquired daily.
I can't find any flaws with the theories or logic.
Another reader did, however, writing: “ ‘If human sexuality developed primarily as
a bonding mechanism in interdependent bands where paternity certainty was a
nonissue, then the standard narrative of human evolution is toast.’ If the standard
narrative of human evolution is, in fact, ‘toast,’ how does their competing worldview
better help explain contemporary human sexual relations?” The book answers this
question with the detailed discussion of agriculture referenced above, noting the
many social, cultural and legal consequences that resulted from land ownership,
hoarding of food, farming, and the need to preserve and pass on private property to
heirs.
The authors further argue that monogamy is simply a cultural construct that arose with agriculture as the logical consequence of abandoning communal living. Once everyone stopped cooperating mutually for each other's survival and farming began, a psychological shift from abundance to scarcity occurred, as resources suddenly became limited, had to be cultivated, hoarded, and sold, rather than gathered communally and distributed equally.
Sexuality followed the same path. By imposing monogamy, men could have some reassurance of their paternity, which became increasingly important, because fathers passed property to their children (unlike in communal times), so paternity certainty became vital to ensure that property was passed to true heirs, not another man's children.
The whole thing is amazing and forces one to reexamine the merit and utility of monogamy, among various other cultural beliefs.
Fun and fantastic read.
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Reviewed in Spain on February 9, 2024















