Sex at Dawn: The Prehistoric Origins of Modern Sexuality
Christopher Ryan, Ph.D. & Cacilda Jethá, M.D.
'Sex at Dawn: The Prehistoric Origins of Modern Sexuality'

Kate Dailey July 26, 2010

Forget what you think you know about the origin of species. Sex at Dawn sets out to prove that our prehistoric ancestors were happy and healthy, thanks in no small part to lots of egalitarian, polyamorous, noisy group sex.

What’s the Big Deal?

This book takes a swing at pretty much every big idea on human nature: that poverty is an inevitable consequence of life on earth, that mankind is by nature brutish, and, most important, that humans evolved to be monogamous. We’ve discussed the
perils of evolutionary biology in this space before, but this book sets out to destroy almost each and every notion of the discipline, turning the field on its head and taking down a few big names in science in the process.


Buzz Rating: Rumble/Roar

Among the scientific set and the intellectuals who think our culture has too many sexual hangups, this book is buzzing.
Andrew Sullivan and Dan Savage spent days on their blogs extolling the virtues of this book, leading to several heated discussions among commenters. The book got writeups in Salon, Glamour, The Washington Post  (twice), The Philadelphia Inquirer, and The Times of London.

One-Breath Author Bio
Ryan is a research psychologist, and has a blog at Psychology Today.  Jethá is a practicing psychiatrist.
Don’t Miss These Bits

Whither the bonobo? When discussing our evolutionary origins, science has a habit of focusing on chimps alone, which are aggressive and cruel. But the authors point out that the peaceable bonobo is just as closely related and may actually have more in common with humans in terms of “socio-sexual behavior and infant development” (page 77). The libidinous bonobos, however, are routinely ignored by researchers, “simply because bonobos raise doubts about the naturalness of human long-term pair bonding” (page 75).

2. Life in the Stone Age was pretty fantastic. Our ancestors were foragers, wandering to find the next savanna when food got scarce. Humanity was so scattered that they rarely had to fight over the best feeding grounds. A varied diet and constant roaming resulted in excellent health: adults grew to be about six feet tall and live long into their 60s and 70s. Foraging tribes show “no evidence of hypertension, heart disease, or cancer. No anemia or common cold. No internal parasites. No sign of previous exposure to polio, pneumonia, smallpox, chicken pox, typhus, typhoid, tuberculosis, malaria, or serum hepatitis” (page 206). The nomadic lifestyle meant they had no sense of property or ownership, so few real reasons for conflict. (John Lennon, are you listening?). Also: group sex.

3. And now we come to the orgy. “Survival of the fittest” applied to our ancestors only at a spermatic level. “The idea is simple. If the sperm of more than one male are present in the reproductive tract of the ovulating female, the spermatozoa themselves compete to fertilize the ovum. Females . . . have various tricks to advertise their fertility, thereby inviting more competitors” (page 220). Rather than men competing with one another to win “entrance” to a coy female looking for the best mate, the book argues that lots of men had sex with the same woman and let their sperm duke it out in the vaginal canal. Even to this day, the initial spurt of human ejaculate contains chemicals that “protect the sperm from chemicals in the later spurts of other men’s ejaculate. These final spurts contain a spermicidal substance that slows the advances of any latecomers” (page 228). That explains, the authors argue, why women take so long to get revved up and men finish so quickly. It explains why women are louder during sex (the so- called female copulatory vocalization [page 255])—it served as a mating call of sorts for men in the area. The survival benefits were immense: since there was no way of telling who fathered which child, children were raised by the community of foragers rather than single monogamous pairs. Everyone had lots of orgasms (women most of all). Women weren’t used as property or bartering chips, which led to more equality between the genders. That’s why men today are more interested in pornography featuring group sex scenes with multiple men and one woman, and why many people have a hard time staying faithful. It’s just not natural. Whew!

Hidden Agenda
It’s not so much hidden: the authors want people to stop deluding themselves about the ease of lifelong commitment. As Ryan said in one of his guest “Savage Love” columns, “Our greatest ambition for Sex at Dawn is that it will encourage young people like you to clarify their sexual nature before signing on to long-term commitments they can’t get out of later without making a huge mess.” The authors have been careful to say that they’re not encouraging everyone to take up with multiple partners, but to be realistic about how humans are designed to operate.

Swipe This Critique
Evolutionary psychology was on shaky ground before this book came out, and Sex at Dawn further rattles the foundations—not by irrefutably disproving those theories (men rape because it’s in their genetic blueprint to spread their seed; women have sex just to keep their sole mate from straying), but by showing how easy it is to piece together prehistoric clues to “prove” a variety of competing conjectures. That said, Ryan and Jethá do an admirable job of poking holes in the prevailing evo-psych theories and are more apt to turn to biological, rather than psychological, evidence. That doesn’t mean their thesis is bulletproof. But it does mean there’s a lot of value in reconsidering basic assumptions about our beginnings that we widely accept today as gospel.

Factoid File
“Testify” is rooted in the practice of swearing an oath by placing one’s hand on another man’s testicles (page 234).


Prose: A. Funny, witty, and light, it makes the 400-plus pages of genetic and anthropological interpretation fly by.

Construction: A. The authors spend a fair amount of time establishing how life might have existed for prehistoric humans when they weren’t having sex, providing their theories with more depth and nuance.

Shock Value: A. This book 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.