Sex at Dawn Reviewed in Journal Evolutionary Psychology

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I was stuck in anthropology/evolutionary theory mode on the train to Austin from the Ancestral Health Symposium in LA. I used a large portion of the time to chip away at rereading Sex at Dawn. My intent was to fulfill my longstanding desire to present a significant critique of the ideas presented in the book. When I first read it, I hadn’t yet launched this site, and didn’t take it too seriously. Unfortunately, it’s become a “bestseller” and is not infrequently referred  to by readers as a potential challenge to my ideas. My criticisms are many (and still forthcoming), but a review just came out in the journal Evolutionary Psychology [pdf] that I feel good about pointing everyone to in the interim.

Just one of my personal quibbles with the book that may give you a little context for my disdain before dumping some of the salient points from review on you. After the authors spend significant time building a largely ad hominem case against Darwin’s ability to comment on sex, they depart from the true picture of modern views on evolved human sexuality by pushing the boundaries of antiquated scholarship beyond their breaking point. Rather than compare Darwin’s ideas to those of modern evolutionary psychologists or anthropologists, they look to Lewis Henry Morgan. Mr. Morgan was indeed a renowned anthropologist, but his death in 1881 precludes him from access to mountains of anthropology relevant (and from other disciplines that are perhaps even more relevant) to questions of natural and sexual selection. Yet, the authors ballyhoo his 19th century authority in an attempt to use his opinions on evolutionary theory to cast aspersion on its modern iteration. Sorry folks, the fact that he was cited by Darwin, Marx, and Freud does not make him well qualified to weigh in on matters of 21st century evolutionary biology. Unfortunately, this sort of faux-authority as literary device to support the Sex at Dawn narrative is a common tactic employed by the authors. The review in Evolutionary Psychology doesn’t add any favorable comments on the scholarship or conclusions forwarded in the book.

The following are quotes from Ryan M. Ellsworth’s piece in Evolutionary Psychology. [bolding for emphasis mine]

One of the more shocking claims in the book is that sexual jealousy isn’t a natural human emotion. I agree with the review that the literature referenced is subjected to a cursory and selective treatment:

In a cursory and selective treatment of the literature, Ryan and Jethá portray sexuality and the relations between males and females in partible paternity societies as carefree, unencumbered by the jealousy and other difficulties and conflicts that attend more restrictive cultural mores. Promiscuous sex creates and promotes webs of affection and affiliation. Further, the institution of partible paternity means that male parental care is diffused, resources are distributed among a wider social network, and children benefit from the investment of multiple fathers. In sum, “Belief in partible paternity spreads fatherly feelings throughout the group”. What the authors fail to mention is that male sexual jealousy and sexual conflict are not absent from even the most sexually liberal of partible paternity societies.

The next two quotes are perhaps most informative regarding the selective and misleading use of the ethnographic record:

It is interesting indeed that Ryan and Jethá approvingly cite some horticultural societies (all partible paternity cultures in South America; the Trobriand Islanders; Tahitians; Mohave) as affirming evidence of the sexually promiscuous nature of humans, and a purported lack of universal concern over paternity, while at the same time rejecting other horticultural societies as representative of ancestral humans in their discussion of warfare on the grounds that they are not foragers. They are attempting to have their cake and eat it, too.

In fact, of all the societies they offer as supporting evidence of a human nature of promiscuous sexuality, only one can truly be considered a foraging population: the Inuit, and it is unfortunate that Ryan and Jethá give only a brief anecdotal nod to the Inuit practice of spouse exchange, leaving out the fact that “Among the North Alaskan Eskimo, wife exchanges were arranged between the husbands, and the wives were not consulted”.

I agree with their assessment that the notion of private property is an emergent property of agricultural civilization, but disagree that sexual jealousy is entangled with either notions of private property or agriculture:

Despite their proclamation that with the dawn of agriculture and the derivative notion of private property, “for the first time in the history of our species, paternity became a crucial concern”, and their description of an “anthropological record so rich with examples of societies where biological paternity is of little or no importance” , the survey of the ethnographic record given by Ryan and Lethá does not lend itself readily to these suggestions. It fares little better in providing support for a promiscuous human nature.

It appears that men everywhere take a proprietary attitude toward female sexuality and strive to monopolize the reproductive resources of their mates. Cross-culturally, adultery (particularly female infidelity) is the most common cause of divorce. Sexual jealousy is the predominant precipitating factor in lethal and nonlethal violence against women, and competition among men over women or the resources needed to attract them has been the cause of much bloodshed in our species. These facts simply are not compatible with the narrative put forth in Sex at Dawn.

When the facts don’t fit the narrative, sometimes you have to change the facts:

Another piece of evidence given for a history of promiscuity is human male testicular size. As noted by Ryan and Jethá, the volume of human testicles relative to body mass is intermediate between gorillas and chimps, and this has been used to argue both sides of the debate over human promiscuity. Recognizing that human testes size doesn’t implicate the levels of bonobo-like promiscuity they see as characteristic of ancestral humans, they resort to the hypothesis that human testes might have been shrinking since the end of the Pleistocene (more so in some racial and ethnic groups than in others) as a result of the increased monandry accompanying an agricultural mode of subsistence. Fair enough, but this is a very difficult hypothesis to test. Luckily, Ryan and Jethá claim that it has already been confirmed! Referring to a paper… reporting that certain genes involved in sperm and seminal fluid production in the lineages of humans, chimps, and bonobos appear to have undergone quite rapid evolution changes. Ryan and Jethá remark that this study… “confirm a prediction made by Roger Short…[that] ‘Testis size might be expected to respond rapidly to selection pressures”’. But nowhere in the… article do the authors mention anything about genes influencing testes size.

Logical problems aren’t uncommon in the text:

Scattered throughout Sex at Dawn are references to mate preference shifts and other cycle-related behavioral changes associated with human estrus. None of the recent evidence on estrus adaptations, however, suggests a history of promiscuity (defined by Ryan and Jethá as a number of ongoing, nonexclusive sexual relationships). Rather, their manifestations are highly contextualized and specific—estrus is not a generalized increase in sexual interest or desire.

This is why I ultimately can’t recommend the book. While I do find the book interesting, its audience seems to be a general public with no serious knowledge of the underlying anthropology or evolutionary theory. The references provided seem to build a convincing case absent the context of a prior understanding of the referenced material. As such, I think this book has already persuaded many people of ill-conceived  ideas, and will likely continue to do so.

Is this book likely to open the eyes of scientists and make them realize that the emperor has, for so long, not been wearing any clothes? Will it initiate a major revision of perspective and research on the evolution of human sexuality among scientists? The answer to both is “no.” But, as mentioned at the beginning of this review, books like Sex at Dawn inform the wider public of the goings-on in academia. In this case, a distorted portrayal of current theory and evidence on evolved human sexuality is presented, and for this reason it deserves more attention from those on the inside.

Perhaps Dr. Ryan’s comment on the review via twitter is the most appropriate summation: “An academic review of S@D (critical, but not terribly unfair).”  - Chris Ryan, PhD.

If you have any comments on the monogamy vs. polygamy question, whether or not sexual jealousy is a real emotion, or other related topics, please share below.