Sex at Dawn

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Sex at Dawn
Sex at Dawn Ryan Jetha 2010.jpg
First Harper Perennial paperback edition cover
Author Christopher Ryan,
Cacilda Jethá
Country USA
Language English
Subject Human sexuality, Anthropology
Publisher Harper
Publication date
June 29, 2010
Media type Print (hardback & paperback)
Pages 384
ISBN 978-0-06-170780-3
LC Class HQ12 .R93 2010

Sex at Dawn: The Prehistoric Origins of Modern Sexuality is a book dealing with the evolution of monogamy in humans and human mating systems. First published in 2010, it was co-authored by Christopher Ryan, Ph.D and Cacilda Jethá, MD (Portuguese pronunciation: [kɐˈsiɫðɐ ʒɨˈta]). In opposition to what the authors see as the 'standard narrative' of human sexual evolution, they contend having multiple sexual partners was common and accepted in the environment of evolutionary adaptedness. Mobile self-contained groups of hunter gatherers are posited as the human norm before agriculture led to high population density. According to the authors, before agriculture, sex was relatively promiscuous, and paternity was not a concern, in a similar way to the mating system of Bonobos. According to the book, sexual interactions strengthened the bond of trust in the groups; far from causing jealousy, social equilibrium and reciprocal obligation was strengthened by playful sexual interactions.

Scholars with expertise in human evolution have been very critical of the book. Their comments on the book have been negative and argue that humans have a history that involves more monogamy than Sex at Dawn acknowledges, that the book misrepresents the current state of research to the general public, and does so deliberately in aid of an "ideological" agenda.[1][2][3] The book has received generally positive reviews in the popular press, with many praising the book's willingness to confront conventional wisdom in an engaging way, and has won several awards, including from clinical researchers and sexologists.


The authors argue that human beings evolved in egalitarian hunter-gatherer bands in which sexual interaction was a shared resource, much like food, child care, and group defense.[1][2][3][4] In this, they agree to a degree with the work of Lewis H. Morgan who proposed in the 19th century that pre-agricultural humans lived in "primal hordes" in which property and paternity was communal.

They think that much of evolutionary psychology has been conducted with a bias regarding human sexuality. The authors believe that the public and many researchers are guilty of the "Flintstonization" of hunter-gatherer society; that is to say projecting modern assumptions and beliefs onto earlier societies. Thus they think that there has been a bias to assuming that our species is primarily monogamous despite what they believe to be evidence to the contrary.[4] They argue for example, that our sexual dimorphism, testicle size, female copulatory vocalization, appetite for sexual novelty, various cultural practices, and hidden female ovulation, among other factors strongly suggest a non-monogamous, non-polygynous history. The authors argue that mate selection was not the subject of much intragroup competition among pre-agricultural humans, as sex was neither scarce nor commodified; rather sperm competition was a more important paternity factor than sexual selection. This behaviour survives among certain existent hunter-forager groups that believe in partible paternity.

The authors argue as a result that conventional wisdom regarding human nature, as well as what they call the standard narrative of evolutionary psychology is wrong.[4] This "standard narrative" goes like this: Males and females assess one another’s mate value from perspectives based upon their differing reproductive agendas/capacities: "He looks for signs of youth, fertility, health, absence of previous sexual experience, and likelihood of future sexual fidelity. In other words, his assessment is skewed toward finding a fertile, healthy young mate with many childbearing years ahead and no current children to drain his resources. b) She looks for signs of wealth (or at least prospects of future wealth), social status, physical health, and likelihood that he will stick around to protect and provide for their children. Her guy must be willing and able to provide materially for her (especially during pregnancy and breastfeeding) and their children (known as male parental investment)." Assuming they meet each other's criteria, they mate and form a monogamous pair bond. Following this, "she will be sensitive to indications that he is considering leaving (vigilant toward signs of infidelity involving intimacy with other women that would threaten her access to his resources and protection)—while keeping an eye out (around ovulation, especially) for a quick fling with a man genetically superior to her husband. He will be sensitive to signs of her sexual infidelities (which would reduce his all-important paternity certainty)—while taking advantage of short-term sexual opportunities with other women (as his sperm are easily produced and plentiful)."[5] They clarify: "we don’t see [the elements of the narrative] as elements of human nature so much as adaptations to social conditions—many of which were introduced with the advent of agriculture no more than ten thousand years ago."[5]

The authors take a broad position that goes beyond sexual behavior, believing that humans are generally more egalitarian and selfless than is often believed. In an interview Ryan said, "we’re not saying that sharing was so widespread because everyone was loving and sitting around the fire singing “Kumbaya” every night. The reason that sharing was so widespread—and continues to be in the remaining hunter-gatherer societies in existence—is because it’s simply the most efficient way of distributing risk among a group of people." [4] However, with the advent of agriculture people's lifestyle changed completely, leading to the advent of private property and the accumulation of power. This fundamentally changed the way people behave and has left the modern human being in a situation where their instincts are at odds with the society they live in.

The authors do not take an explicit position in the book regarding the morality or desirability of monogamy or alternative sexual behavior in modern society, but argue that people should be made aware of our behavioral history so that they can make more informed choices.[6]


While the reception in the popular media to Sex at Dawn has been generally positive, reviews from academics with expertise in evolution and human sexuality have been mixed. Scholars with expertise in human evolution have been very critical while researchers/clinicians in human sexuality have been supportive.

Popular media reception[edit]

One month after publication, Sex at Dawn entered The New York Times best-seller list.[7] The book was praised by syndicated sex-advice columnist Dan Savage, who wrote: "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."[8][9] Newsweek's Kate Daily wrote, "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. ... [Sex at Dawn] 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. ... Funny, witty, and light ... the 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... 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."[10]

Eric Michael Johnson, writing in Seed Magazine, said "by looking at modern indigenous societies and comparing the findings of anthropologists with the latest results in behavioral psychology and biology, Ryan and Jethá piece together a remarkably coherent pattern from an otherwise fractured understanding of human sexuality." He further commented that the findings were not as novel as sometimes presented, noting that Sarah Hrdy "advocated a promiscuous mating system for humans in The Woman That Never Evolved" in 1999 and psychologist David Barash and psychiatrist Judith Lipton had detailed their own arguments in a similar vein in 2001.[11] However, this book updated the ideas with material not available a decade earlier and did so using a "relaxed writing style and numerous examples from modern popular culture, their discussion of these topics remains readily accessible even to those who may be encountering such ideas for the first time."[11] The book was chosen as NPR host Peter Sagal's favorite book of 2010,[12] and was chosen as one of the best science and technology books of 2010 by[13]

Harvard University immunology graduate student and science blogger Kevin Bonham wrote that "Ryan and Jethá conclude that pre-agrarian human societies were exceedingly promiscuous. Drawing on archeological, behavioral and anatomical evidence, as well as analysis of extant pre-agrarian human societies and our closest primate relatives, the authors build an argument with page after page of clear, convincing and often humorous discussion," but cautions "I can’t be certain that the authors aren’t cherry-picking examples that support their conclusions."[14] Megan McArdle writing on her blog at The Atlantic was critical, stating that "it reads like an undergraduate thesis--cherry-picked evidence stretched far out of shape to support their theory. The language is breathless rather than scientific, and they don't even attempt to paper over the enormous holes in their theory that people are naturally polyamorous." [15]

Reception from experts in the field[edit]

The book received the 2011 Ira and Harriet Reiss Theory Award from the Society for the Scientific Study of Sexuality.[16] It also won the 2011 SSTAR Consumer Book Award (Society for Sex Therapy and Research).[17] However, according to Ryan, the book was rejected by Oxford University Press after 2 of 3 peer reviews by primatologists were negative during the publisher's internal peer review process.[18]

The book has been criticized for its alleged "biased reporting of data, theoretical and evidentiary shortcomings, and problematic assumptions" in a pair of book reviews by Ryan Ellsworth, graduate student in anthropology[3][19] at the University of Missouri, in the peer reviewed journal Evolutionary Psychology. Ellsworth argues that the book misrepresents the state of current research on sexual behavior. In particular, Ellsworth criticizes the authors for drawing too many conclusions from too little evidence, charging that "if promiscuity even slightly approaching bonobo levels were characteristic of (post-Homo erectus) ancestral sexuality, there would be much more evidence for it than Sex at Dawn manages to drum up. Ryan and Jethá conjure up a phantom of human nature that vanishes in the face of scrutiny—a naïve vision of a human that never evolved." Ellsworth notes that while promiscuity has certainly been part of human behavior, it is "doubtful that this is because we are promiscuous at heart (this may apply to the behavior of most women more than the desire of most men), shackled by the trappings of a post-agricultural dilemma of our own devices, unable to return to the ancestral days of sexual communism." Writing that he could find no previous academic reviews of Sex at Dawn, Ellsworth faults his fellow academics for failing to give the book the attention he believes it deserves, because its popularity may result in "a distorted portrayal of current theory and evidence on evolved human sexuality" gaining credibility with the general public.[2][3]

Christopher Ryan has argued that Ellsworth's review made some valid points, but that overall it misrepresented the argument of Sex at Dawn. Ryan did not believe that he and Jethá had argued that human sexuality was the same as bonobo sexuality; rather, that coitus was more frequent than is generally acknowledged, and that a typical human being would have had multiple partners within relatively short periods of time (i.e. each estrus cycle of a female). He argues that the main thrust of the book is to discredit "the standard narrative," which he believes it does. He believes reviewers read too much into the book, which he thinks does not argue specifically in favor of a particular, universal model of human sexuality, except to say that there is rather less monogamy than traditionally believed.[18] Ryan also alleged that the academic review process "shuts down alternative views" and that some of the negative reaction from academics was due to the fact that many felt threatened by new ideas which could threaten reputations or positions.[18]

In an approving Chronicle of Higher Education review of Sex at Dusk — a rebuttal to Sex at Dawn written and self-published by Lynn Saxon — David Barash, author of The Myth of Monogamy: Fidelity and Infidelity in Animals and People wrote that Ryan and Jethá "ignore and/or misrepresent reams of anthropology and biology in their eagerness to make a brief for some sort of Rousseau-ian sexual idyll that exists—and/or existed—only in their overheated libidinous imaginations."[1] Barash quotes Saxon's critique that "Sex at Dawn is almost all about sex and not much about children, yet evolution is very much about reproduction – variation in reproductive success is evolution" and argues that he finds it annoying that Sex at Dawn "has been taken as scientifically valid by large numbers of naïve readers … whereas it is an intellectually myopic, ideologically driven, pseudo-scientific fraud." In short, "just as multiple sexual partners can increase the fitness of a philanderer, the same behavior on the part of one’s partner can reduce the other’s fitness. Hence, sexual jealousy is a very widespread and fitness-enhancing trait, as is a roving eye."[1] Ellsworth also discussed Saxon's arguments in a follow-up review. He agreed with many of her criticisms of Sex at Dawn, including what she regards as the book's superficial discussion of bonobo and chimpanzee sexuality, an over-emphasis on the importance of sperm competition, ignoring the role of philopatry and emigration, complicated human inter-group relationships, and major omissions from the paleoanthropological record among others. Ellsworth agrees with Saxon that the omissions must be intentional, in service of an ulterior "ideological" agenda since they claim the information they point to is available in the sources cited by the book.[3]


  1. ^ a b c d Barash, David (21 July 2012). "Sex at Dusk". The Chronicle of Higher Education. Retrieved 27 July 2012. 
  2. ^ a b c Ellsworth, Ryan (2011). "The Human That Never Evolved". Evolutionary Psychology. 3 9: 325–335. Retrieved 24 May 2012. 
  3. ^ a b c d e Ellsworth, Ryan (2012). "The myth of promiscuity: A review of Lynn Saxon, Sex at Dusk: Lifting the Shiny Wrapping from Sex at Dawn". Evolutionary Psychology. 3 10: 611–616. 
  4. ^ a b c d Seidman, Barry F.; Arnell Dowret (March–April 2011). "Speaking of Sex". Humanist Magazine. Retrieved 7 February 2013. 
  5. ^ a b Ryan, Christopher. "Inquisition". Retrieved 15 March 2013. 
  6. ^ Christopher Ryan, Ph.D. & Cacilda Jethá, M.D. "Frequently Asked Questions about Sex at Dawn". Sex at Dawn Official Website. Retrieved 7 February 2013. 
  7. ^ "Hardcover Nonfiction Bestseller list". The New York Times Sunday Book Review. August 8, 2010. Retrieved 8 July 2011. 
  8. ^ Savage, Dan (July 8, 2010). "Sex at Dawn". 
  9. ^ Patel, Khadija (2011-03-17). "'Sex At Dawn': shattering the monogamy myth, and more". Daily Maverick. Retrieved 2013-06-14. 
  10. ^ Dailey, Kate (July 26, 2010). " 'Sex at Dawn: The Prehistoric Origins of Modern Sexuality' ". Newsweek. 
  11. ^ a b Johnson, Eric Michael (29 June 2010). "Sexy Beasts". Seed Magazine. Retrieved 17 January 2013. 
  12. ^ Sagal, Peter (2 December 2010). "Favorite Books Of 2010: Peter Sagal On 'Sex At Dawn'". National Public Radio. Retrieved 17 January 2013. 
  13. ^ "Best Science and Technology Books of 2010". 
  14. ^ Bonham, Kevin. (17 June 2011) Let’s talk about sex (at dawn), We Beasties. Science Blogs.
  15. ^ Mcardle, Megan (30 August 2010). "Is Monogamy Unnatural?". The Atlantic. Retrieved 25 June 2014. 
  16. ^ "The Ira and Harriet Reiss Theory Award". Retrieved 9 November 2012. 
  17. ^ Ryan, Christopher (2011-02-19). "Top Ten Sex at Dawn Posts From 2010". Psychology Today. Retrieved 2013-06-14. 
  18. ^ a b c Christopher Ryan (14 March 2013). "21 - Special Sex at Dawn Episode (B): Response to Criticism" (Podcast). Tangentially Speaking. Retrieved 14 March 2013. 
  19. ^ "Ryan Ellsworth". Retrieved 25 July 2013. 

External links[edit]