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

This review originally appeared in Seed Magazine: http://seedmagazine.com/content/article/sexy_beasts/

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.

For Ryan and Jethá there is little doubt that human beings are an exceedingly sexual species. As an example they detail how in 1902 the first home-use vibrator was patented and approved for domestic use in the United States. Fifteen years later there were more vibrators than toasters in American homes (today this number could be as high as fifty million nationwide). In 2006, according to U.S. Pornography Industry Revenue Statistics, people around the world--the majority of whom were probably men--spent an estimated $97 billion on pornographic material ($13.3 billion in the U.S. alone), a figure that exceeded the annual revenue of Microsoft, Google, Amazon, eBay, Yahoo!, Apple, and Netflix combined. To judge human sexuality based on consumption patterns, as Stephen Colbert would say, "the market has spoken." When this is combined with estimates that people engage in hundreds, and sometimes thousands, of copulations per child born (more than any primate, including chimpanzees and bonobos) there's little denying that the human animal is one sexy beast.

But why should a species often described as monogamous be so hypersexual? Monogamous animals by definition don't have to compete for reproduction and, as a result, are generally characterized by a low level of sexual activity. But according to Ryan and Jethá humans top a very short list of species that engage in sex for pleasure. "No animal spends more of its allotted time on Earth fussing over sex than Homo sapiens," they write. In fact, the animal world is filled with species who confine their sexual behavior to just a few periods each year, the only times when conception is possible. Among apes the only monogamous species are the gibbons whose infrequent, reproduction-only copulations make them much better adherents of the Vatican's guidelines than we are. In this way, Ryan and Jethá argue, repressing our sexuality should not be confused with reining in an "animal" nature; rather, it is denying one of the most unique aspects of what it means to be human.

The suggestion that humans did not evolve as a monogamous species is not as radical an idea as it may sound. In The Descent of Man Charles Darwin wrote, "Those who have most closely studied the subject [particularly the anthropologist Lewis Henry Morgan] believe that communal marriage was the original and universal form throughout the world." Yet ever since the nineteenth century anthropologists have struggled over how to identify the mating system of human beings. In 1967 George P. Murdock's Ethnographic Atlas reported that only 14.5% of modern preindustrial societies could be classified as monogamous. Yet, in the West, researchers commonly refer to humans as "serially monogamous," based on the pattern of repeated monogamous marriages throughout men and women's lifetimes. But with over half of divorces occurring because of infidelity and one in 25 dads unknowingly raising children that they didn't father, this is not a picture that fits comfortably with monogamy of any sort, serial or otherwise.

However, 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. From societies that believe that multiple men are necessary for a successful pregnancy (what researchers refer to as "partible paternity") to those where not having an extra-marital tryst will cause a man to be labeled "stingy of one's genitals" by his female suitors, the authors conclude that marriage may be an established social arrangement among many hunter-gatherers but it's one in which sexuality is decidedly fluid. A range of physiological evidence from Western populations is further offered to support this position, from the year-round libido in both sexes, to the unusually large size of men's genitalia compared to other apes, to the shifting sexual strategy during various stages in women's reproductive cycle (and lest we forget multiple female orgasms?). All suggest that our species is adapted for several concurrent sexual partners.

This is, of course, not a new idea in human evolutionary research. Primatologist Sarah Hrdy advocated a promiscuous mating system for humans in The Woman That Never Evolved (1999) while psychologist David Barash and psychiatrist Judith Lipton detailed their own argument in The Myth of Monogamy (2001). In Sex At Dawn Ryan and Jethá cover some similar ground as these previous authors but provide a great deal of additional material that was unavailable a decade ago. They also emphasize the ways in which monogamy has been used as a means of controlling women in patriarchal societies and make a number of insightful connections between the invention of agriculture 12,000 years ago and how sedentary societies influence the structure of human mating. However, with 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.

Sex At Dawn is a provocative and engaging synthesis of the latest research on human sexual evolution that has the added benefit of being a joy to read. While the authors' conclusion that healthy relationships can be both committed and open may come as a shock to some readers, others will likely find it refreshingly honest. As their example of WWII fighter pilots emphasizes, human sexuality has numerous social as well as emotional functions and there has never been only a single path chosen by the human species. In offering a fresh look at a fascinating and controversial topic Sex At Dawn is a book sure to generate discussion, and one likely to produce more than a few difficult conversations with family marriage counselors.

Eric Michael Johnson received his masters degree in primate behavior and is now pursuing his PhD in the history of science. He writes on issues of science, politics, and history at The Primate Diaries.

This was a terrific read -- a sweeping (and well written, and funny) look at recent anthropological, zoological, and biological research all leading to a mind-bender of a conclusion: our prehistoric ancestors were wall-to-wall horndogs, men and women alike, with "multi-male/multi-female" sexual relations the likely norm for 95 percent of anatomically modern humans' existence. The nuclear family centered on a pair-bonded husband and wife, and the monogamy that comes with it, probably only date to the last 8,000-10,000 years, since the advent of agriculture.

Ryan and Jethá dismantle the more common Men-are-from-Mars, Women-are-from-Venus view -- i.e. men have a biological imperative to impregnate as many women as possible while keeping their wives monogamous so they (the men) support only their own genetic offspring, while women want to bond with wealthy, high-status males for their resources, but also to sleep around with the bad boys for their genes. R&J make a strong case that this sort of arrangement could only make sense in post-agricultural societies where concepts of property and paternal lineage become important, but that it would be meaningless in the hunter-gatherer groups that were the only form of human society for almost 200,000 years. When they get into the section on "sperm competition," things get reaaaally trippy.

The book kind of leaves you hanging as far as what this information means for modern humans, but that's probably a virtue. We have after all changed quite a bit from prehistoric times, and it's not as though our evolutionary history has to dictate our moral or social behavior today. Nowhere do the authors say everybody should walk out of their marriages and form hippie communes or anything like that. Instead, they say their goal is to start a conversation -- about sex, and how our prehistoric urges may help explain why so many people have trouble staying with one partner over their whole lives. It's a conversation-starter, all right.

I was tempted to take one star away because I felt throughout like they weren't presenting opposing views in the best light, but hey, it's a polemic. And it's a fun one, too. So let the arguments begin.

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. what gets expressed) is a function of genotype (the genes), the environment (the sum of all external influences, food, temperature, etc), and ontogeny (our development). In its simplest form, any given genotype has a phenotype that responds in complex and varied ways relative to the environment -- this is known as a "norm of reaction" ([...]). When barley is grown a low altitude it behaves very differently form when it's grown a high altitude -- so it makes little sense to ask "what is the true nature of barley" because there is no such thing. Seeking the "true nature" of a species is a holdover from ancient notions of Greek essentialism, which we now know is fundamentally wrong. It is just as "natural" for an all-sharing-commune to also share sex freely, or for a married couple (where the husband invests considerable paternal care) to desire sexual exclusivity (even if this is not always achieved), or for new brides to willingly join in the polygynous family of a wealthy and powerful man -- i.e., depending on the environment, we should expect humans to behave quite differently, and each case is just as "natural" as any other. There is no single "human nature" to be discovered -- at best, we can say that there is a norm-of-reaction to be discovered.

Humans have clearly evolved complex and distinct behaviors capable of responding differently in each distinct environment. That by itself is remarkable, and although Ryan and Jethá are convincing when then claim that bonobo-like behaviors were common in human pre-history, they fail to show that human pre-history did not also include quasi-monogamy (as is now dominant), serial-monogamy, and various degrees of polygyny. Given the wide range of habitats that humans lived in (tundra, boreal forest, rain forest, savannah, estuaries, island archipelagoes, etc) it certainly should not surprise us that humans have adapted to a multitude of different circumstances. Ryan and Jethá argue that a history of intense sperm competition is written on our bodies -- and that may well be true, but it's not incompatible with quasi-monogamy, serial-monogamy, or polygyny. Who can say how many children, born to the king's concubines, were actually fathered by the game-keeper? And if, as some studies claim, some 10% to 20% of kids are not actually the children of the fathers who think they are his children, that by itself is more than enough selection pressure to evolve larger testicles. Finally, the two-fold size difference in European and Asian testicles would seem to imply that some radically different mating systems were present in the pre-agricultural years during the separation of these two populations.

Finally, Ryan and Jethá are guilty of the naturalistic fallacy -- believing that what is "natural" is also good. They may deplore the frustrated husbands who seek out porn to quiet their bonobo impulses, but how about the frustrated bullies who suffer in prison for merely exercising their evolution-given muscles to resolve a dispute? Surely many a dispute in pre-history was resolved by men using brute force to the reproductive advantage of the winner, which is why men are more muscular than women. Does that make it unfair for us to outlaw crime or domestic abuse? Why should promiscuity be any more "natural" than bulling?

Nonetheless, the general point that humans need to learn to relax about social morays is a good one. We are certainly capable of far greater latitude in our mating behaviors than what our priests, politicians, and grandmothers would have us believe. The advent of reliable contraception and an increasing number of self-sufficient women in the workplace ought to allow society to attenuate urges of sexual jealousy and liberalize our relationships -- but without having to give up our privacy, possessions, and suburban homes in favor of communes.