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Sex at Dawn: How We Mate, Why We Stray, and What It Means for Modern Relationships [Kindle Edition]

Christopher Ryan , Cacilda Jetha
4.3 out of 5 stars  See all reviews (440 customer reviews)

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Sold by: HarperCollins Publishers

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Book Description

Since Darwin's day, we've been told that sexual monogamy comes naturally to our species. Mainstream science—as well as religious and cultural institutions—has maintained that men and women evolved in families in which a man's possessions and protection were exchanged for a woman's fertility and fidelity. But this narrative is collapsing. Fewer and fewer couples are getting married, and divorce rates keep climbing as adultery and flagging libido drag down even seemingly solid marriages.

How can reality be reconciled with the accepted narrative? It can't be, according to renegade thinkers Christopher Ryan and Cacilda Jethå. While debunking almost everything we "know" about sex, they offer a bold alternative explanation in this provocative and brilliant book.

Ryan and Jethå's central contention is that human beings evolved in egalitarian groups that shared food, child care, and, often, sexual partners. Weaving together convergent, frequently overlooked evidence from anthropology, archaeology, primatology, anatomy, and psychosexuality, the authors show how far from human nature monogamy really is. Human beings everywhere and in every era have confronted the same familiar, intimate situations in surprisingly different ways. 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.

With intelligence, humor, and wonder, Ryan and Jethå show how our promiscuous past haunts our struggles over monogamy, sexual orientation, and family dynamics. They explore why long-term fidelity can be so difficult for so many; why sexual passion tends to fade even as love deepens; why many middle-aged men risk everything for transient affairs with younger women; why homosexuality persists in the face of standard evolutionary logic; and what the human body reveals about the prehistoric origins of modern sexuality.

In the tradition of the best historical and scientific writing, Sex at Dawn unapologetically upends unwarranted assumptions and unfounded conclusions while offering a revolutionary understanding of why we live and love as we do.

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Editorial Reviews


“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.”


"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

Product Details

  • File Size: 1467 KB
  • Print Length: 420 pages
  • Page Numbers Source ISBN: 0061707805
  • Publisher: Harper Perennial; Reprint edition (March 27, 2012)
  • Sold by: HarperCollins Publishers
  • Language: English
  • ASIN: B007679QTG
  • Text-to-Speech: Enabled
  • X-Ray:
  • Lending: Not Enabled
  • Amazon Best Sellers Rank: #9,699 Paid in Kindle Store (See Top 100 Paid in Kindle Store)
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Customer Reviews

Most Helpful Customer Reviews
587 of 637 people found the following review helpful
5.0 out of 5 stars Sexy Beasts July 4, 2010
This review originally appeared in Seed Magazine: [...]

When we think of the first swinger parties most of us imagine 1970s counter-culture, we don't picture Top Gun fighter pilots in World War II. Yet, according to researchers Joan and Dwight Dixon, it was on military bases that "partner swapping" first originated in the United States. As the group with the highest casualty rate during the war, these elite pilots and their wives "shared each other as a kind of tribal bonding ritual" and had an unspoken agreement to care for one another if a woman's husband didn't make it back home. Like the sexy apes known as bonobos, this kind of open sexuality served a social function that provided a way to relieve stress and form long-lasting bonds.

For the husband and wife team Christopher Ryan and Cacilda Jethá in their new book Sex At Dawn, this example is one of many that suggests the human species did not evolve in monogamous, nuclear families but rather in small, intimate groups where "most mature individuals would have had several ongoing sexual relationships at any given time." We are the descendants of these multimale-multifemale mating groups and, even though we've constructed a radically different society from our hunter-gatherer forebears, the behavioral and psychological traits our species evolved in the distant past still manifest themselves today. Ryan, a psychologist, and Jethá, a psychiatrist, argue that understanding human sexual evolution this way helps to explain our species' unique creativity inside (as well as outside) the marriage bed. It may also shed light on why fidelity has been such a persistent problem for both men and women throughout recorded history.
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539 of 603 people found the following review helpful
3.0 out of 5 stars Amusing but flawed. March 26, 2011
Format:Hardcover|Verified Purchase
This is an amusing and light read, salted with sarcastic quips and, of course, covering a salacious topic. It endeavors to refute the "common wisdom" of just about every field (history, biology, anthropology, etc.) on the subject of human mating systems, and while it appears to succeed here and there, it is largely done by attacking an exaggerated straw man, or by refuting overstatements made in popular science books or in newspaper articles. The lion's share of sources includes the likes of Matt Ridley, Desmond Morris, E. O. Wilson, and Richard Dawkins -- authors who (1) are rarely actively pursuing primary scientific research in what they write about, and (2) are writing for the general public, with, naturally, a tendency to exaggerate and generalize -- so these popular texts are easy targets. At times, Ryan and Jethá demonstrate an imperfect understanding of evolution (e.g. no evolutionary biologist needs to ask the rhetorical question at the end of the middle paragraph on p. 53); at other times they allow inconsistencies to slip by unaddressed. For example, if the true state of hunter-gatherer humans is to share everything, show no jealousy, and for women not to barter with sex, how is it that the bride and groom at a Canela marriage must be instructed not to be jealous (p. 138), or that a Canela bride-to-be participates in orgies in exchange for meat (p. 120)? Overall, it's an entertaining, quick read, but not without flaws in some of its claims and conclusions.

The biggest shortcoming of this book is its epistemological framework: it seeks to uncover our true "human nature," but "human nature" itself is a flawed concept, and early sociobiologists were long-ago admonished for using this term. Biologists know that phenotype (i.e.
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144 of 169 people found the following review helpful
By AronH
Format:Paperback|Verified Purchase
I have a copy of the book. I was amazed with the number of errors, the amount of misinformation, the flawed assumptions, and even more so with the degree to which the book has received positive reviews. I believe that this is at least partly because this book appeals to individuals who have already made up their minds on this topic.

However, the audience aside, this books seems to appeal to us because we know that having sex with one partner doesn't necessarily make us immune to thoughts of having sex with someone else. So we conclude that there must be something wrong with the idea that human beings develop bonds. We therefore assume that this book is correct in asserting that we are a promiscuous species.

Unfortunately, it seems too many of us have forgotten that the scientific idea of bonding never implied that we automatically become immune to feeling sexually attracted to alternative partners. In the field of biology and attachment, sexual bonding creates what is called a "partner preference." Note that the key term here is "preference"!

PLEASE, see the 1994 study "Oxytocin Administered Centrally Facilitates Formation of a Partner Preference in Female Prairie Voles (Microtus ochrogasfer)" for just one example of this concept of partner PREFERENCE.

Funny thing is...we already know that, in the absence of alcohol, neurologically active hormones like Oxytocin are implicated in bonding. We also already know that Oxytocin affects the development of a woman's attachment to her romantic partner. I have no idea how the authors missed this. It's probably because they were never academically qualified to write a book on this topic in the first place.
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Most Recent Customer Reviews
5.0 out of 5 stars wow, truly a ground breaking book
This book has changed my perspective on so many things. It has alleviated much of my wonderings regarding sexuality contradictions and taboos. Read more
Published 16 hours ago by Nb
5.0 out of 5 stars This book is a book
I did not read this but I bought it for a friend and she gives it five stars funk dat
Published 21 hours ago by Steven Anthony Furio
2.0 out of 5 stars Provocative but ultimately badly written
They write like Slate: great titles, great opening sentences, but shoddy research, no follow through, no sense that they really read or understood what they were reading. Read more
Published 2 days ago by Beatrice Izzey
5.0 out of 5 stars Never thought about that....
Human behavior has always fascinated me, hence I've always been fascinated by Human Sexual behavior, mine as well as others. Read more
Published 3 days ago by brus
2.0 out of 5 stars A fantasy view of our sexual nature
This book is a direct attack on monogamy. The arguments range from fallacious to the ridiculous. Since the hunter/gatherers shared food, they must have shared mates! Read more
Published 5 days ago by John Colwell
4.0 out of 5 stars Great ideas, but maybe too much about primates.
A new way to look at the world of sex, but maybe a bit too much about primates. I know it was the foundation, but that part lagged a bit. A book that may be revolutionary. Read more
Published 8 days ago by John Oshea
5.0 out of 5 stars Everyone should read this book.
I wish that we would come together as a collective and look at our views on sexuality, acknowledge were they come from, and move on to a healthier outlook.
Published 13 days ago by motormadam
5.0 out of 5 stars it opened my eyes
I've heard and read so much about monogamy as the "natural" human sexuality and couldn't explain why people (men and women) cheat so much.. Read more
Published 14 days ago by Eliane Barreto
5.0 out of 5 stars A mindset-altering book.
I am now working through Sex at Dawn, a somewhat controversial book by the anthropological psychologist Christopher Ryan and medical doctor Cacilda Jetha. Read more
Published 15 days ago by Adam Ford
5.0 out of 5 stars Could reading for any serious relationship!
My wife and I enjoyed the book immensely. we each had our own copies so we could mark them up. It has sparked many entertaining discussions.
Published 18 days ago by Kenneth P. Hutchison
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More About the Author

Christopher Ryan, Ph.D.
Christopher received a BA in English and American literature from Hobart College in 1984 and an MA and Ph.D. in research psychology at Saybrook University twenty years later. He spent the intervening decades traveling around the world, living in unexpected places working at very 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). Somewhere along the way, he decided to pursue doctoral studies in psychology. Drawing upon his multi-cultural experience, Christopher's research focused on trying to distinguish the universally human from the cultural. His doctoral dissertation analyzes the prehistoric roots of human sexuality, and was guided by the world-renowned psychologist, Stanley Krippner.

Based in Barcelona since the mid 1990s, Christopher has lectured at the University of Barcelona Medical School and worked as a consultant at various local hospitals. He's given presentations around the world (in both English and Spanish), and published peer commentaries, scientific and popular articles as well as book chapters. His work can be found in publications such as Behavioral and Brain Sciences (Cambridge University Press), SAGA: Best New Writing on Mythology (White Cloud Press), and a text book used in medical schools and teaching hospitals throughout Spain and Latin America.

Check out Christopher's blog at


Cacilda Jethá, M.D.
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 reside together in Barcelona, Spain, where she is a practicing psychiatrist at Hospital San Joan de Déu and in private practice. She speaks Portuguese, French, Spanish, Catalán, English, and some rusty Swahili.

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