Posted by: Chris | July 7, 2010

Biology and Destiny

Sex at Dawn, a new book by psychologists Christopher Ryan and Cacilda Jetha, purports to discuss the evolution of human sexuality.  But the focus of the book, at least from the reviews and the series of Q&A’s the authors have on their own website, seems to be in a very narrow subset of the same: dispelling the idea of biologically enforced monogamy, as well as promulgating some neo-tribalist pap along the way. 

Though I have couple problems with their theses, I cannot fault evidence they cite and the biological conclusions they come to.  Humans, like all great apes (and really all mammals), are by nature sexually polygamous.  Men especially seek out not only multiple mates over a lifetime, but also multiple mates simultaneously (this behavior, of course, is not unheard of in females, either: a female chimpanzee in estrous will often seek out as many males as possible to mate with).  They look not only to behavioral observations, but also physiological adaptions which belie our polygamous past, like sperm and penile modifications to improve ones chances of conception in inter-sperm competition.  Additionally, if the FAQs can serve as a representative sample, they also have a bunch of nifty fun facts to flesh out their thesis.  For example, the relationship between hormone levels and infidelity:

1. Why do middle-aged men risk so much for flings?

With the caveat that every situation is different, one factor we think deserves more attention is the role of testosterone (T) in middle-aged men’s eroticism. In their twenties, men’s T levels begin a long decline, often experienced as diminished passion and appetite for life. Suppressed T levels are associated with depression, heart attacks, dementia, and overall mortality rates from 88 to 250 percent higher. One of the few things that can reliably and immediately revive a man’s sagging testosterone is exposure to a new woman. One researcher found that even a brief chat with an attractive woman raised men’s testosterone levels by fourteen percent within minutes. In Sex at Dawn, we suggest that many men may be confusing the hormonal changes triggered by an affair with actual “love,” thus leading them to make ill-advised decisions catastrophic to their families, their marriages, and eventually themselves.

The only issue with the science of the book is the authors make their theories seem much more controversial than they are.  This all was presented, quite regularly, as the undisputed mainstream interpretation of things in undergraduate biology courses.  Indeed, I’ve read most of their fun facts first in staid textbooks.  I suspect the author’s posturing as non-conformist rebels pushing back against a fictional “biological monogomy” consensus has to do with a) inflating the publicity and importance of the book and b) their writing for a less biologically literate audience, for whom this approach may seem much less than conventional.

However, once the book moves towards applying these biological truths to human society and history and especially when they delve into prescription about human behavior, their ideas become much more suspect.  At the heart of my objections, I find the idea that the preceding research validates lifting social sanctions against polygamy absolutely ridiculous.  The authors argue that we should “seek peace with the truths of human sexuality” and that, to quote a reviewer, “we embrace a sexuality that does not diminish the energies wired into our essential selves.”

The problem here is, as biologically unnatural as it may be, enforced monogamy plays an incredibly important role in maintaining social stability and forms the bedrock for the greater organized society.  These authors seem to intentionally avoid the truism that Jon Rauch is fond of repeating: polygamy implies polygyny.  This is especially surprising since this flows from the very data Ryan and Jetha discuss.  Males, and especially mammalian males, due to biological forces that (if one were to be quite reductionist) flow back to gamete size, will necessarily have a greater appetite for sex, will seek out more partners, and will have less involvement with child-rearing.  This leads to an equilibrium state of a few males having many female partners and quite a few males missing out (as gender ratios are 50-50).  Indeed, this is the natural social organization of most mammal species, including all the non-human great apes.  

This arrangement, however, is simply unsustainable in human populations, especially those that reach a critical mass in which complex hierarchical and political organization is inevitable.  A large population of sexually frustrated, disempowered men capable of joint action does not produce a stable society.    Monogamy reduces intra-relationship conflicts as well, as there is no one to compete with for the affection of their partner.  I once read a defender of polygamy write that love is not some finite quantity to be divvied up amongst claimants, but an amorphous thing, that can be shared equally and fully to all, a parent does to their offspring.  I can only assume this person was an only child.  Child-rearing, too, suffers under polygamous and polyamorous relationships.  The broad consensus is that children need a stable home with two parents who have raised them from infancy.  The revolving door of parent-surrogates that non-monogamous relationships provide not only deprive children of the environmental regularity they require at home, it also exposes them to adults much more likely to abuse/neglect them (for the obvious Darwinian reason that the kids don’t carry their genes and the brain can’t be tricked into thinking otherwise).

Polygamy of the “free love” sort the authors prescribe is rife with further problems.  Any society that enforces life-bonding, including polygynous ones like the FLDS compounds, isolates the tensions, conflicts, and jealousies of sexual competition and tumult into a small subset of the population (from roughly post-pubescents to young adults).  Once people settle down, they live an uncontentious, if sometimes uncontented, life, punctuated by the occasional divorce or infidelity.  Monogamous social norms often interfere with individual compulsions and preferences, which the authors seem to value primarily (see their marriage should be a choice spiel in the Q&As), but they are necessary for maintaining social cohesion and harmony for reasons most biologists would find apparent, which of course buttresses individual wellbeing much more in the long run.

This gets to something I did not really bring up back when we had that Orwell inspired discussion about social norms curtailing honest behavior and free will.  I actually generally tend to sympathize with the adherence to social norms side of things, even (somewhat) in the case I brought up about false modesty.  However, I think the institution of marriage as an enforcer of monogamy is one of the best examples of the efficacy of social norms.  I suspect, if our only concern was individual preferences, then a Boazian system of bonding through contract law would, at least facially, maximize the utility of most people.  We certainly would not lard up marriage with such an irrational amount of mystique and expectation.  But society’s excessive obsession with pressuring those who aren’t married to do so and equally excessive sanctioning of those who succumb to their biological destiny and commit infidelity is what maintains the expectation of monogamy that undergirds society, and, in the end, prevents individual lives from being far worse off.  People like Ryan and Jetha will get exasperated with those who would condemn an adulterer who was only acting as nature intended, but the entirety of civilization rests upon resisting our natural inclinations, not just toward sex, but toward consumption, violence, and wanton enjoyment.

Ryan and Jetha are at least consistent in this regard: also seem to have a problem with the entirety of civilization.  Mixed into a book about the evolution of sex, they include a mess of neo-tribalist tropes, like the noble savagery of our hunter-gatherer ancestors and the original sin of agriculture:

It’s almost impossible for most of us to appreciate how radically different the social world of our ancestors was from what we experience today. Anthropologists agree that pre-agricultural societies almost universally share a passionate commitment to so-called “fierce egalitarianism.” Because they are nomadic, such people accumulate as little personal property as possible, thus resulting in cultures organized around sharing. Food, shelter, child-care, protection from predators . . . all are scrupulously shared.

With the advent of agriculture just 10,000 years ago (less than 1/20th of our existence as anatomically modern Homo sapiens), personal property became all-important. Families accumulated land, buildings, status, and wealth that they wanted to keep in the family. The only way a man could ensure his paternity was through strictly controlling his wife’s (or wives’) sexual behavior. Thus, female infidelity has been ruthlessly punished for millennia. Most evolutionary psychologists assert that male obsession with controlling female sexual behavior is intrinsic to human nature, but the evidence we present in Sex at Dawn shows it to be a response to economic conditions that arose with farming.

This is all, quite frankly, bullshit.  One, the male sexual domination of females and prevention of female infidelity did not begin with farming.  It does not even begin with humanity.  As we said earlier, most mammals and all great apes are polygynous.  They keep harems of females to mate with and violently ward off any males who might try to copulate with their females.  We are not even the most egregious offenders.  Elephant seals, for example, take huge harems, where one or two dominant males might control nearly the entire female population with the rest receiving none at all.  They maintain their domination of the females and protect against being cuckolded through continual perverse sexual selection for immense girth.  Male elephant seals can weigh up to five tons (making them the largest member of Carnivora, much much larger than any bear or large cat) and regularly outweigh females by a factor of 3, solely for the purpose of sexual control, to the detriment of their dexterity in water.  The average male spends nearly all their time fighting with other males or copulating with the females it owns (or trying to sneak in, for the vast majority without harems).  The “male obsession with controlling female behavior” is not only intrinsic to human nature, its intrinsic to nature more generally.  I also have no idea where the authors figured out that the advent of agriculture resulted in the average male hording a host of belongings that they would want to pass along.  I always assumed the advent of farming resulted in people becoming property, not gaining it.  The incentive for preventing other males from having sex with a female was the same as it ever was: so that you can have more kids and spread your genes as widely as possible.  To think these people call themselves Darwinists.

The noble savage side of the neo-tribalist coin is predicated more on misrepresentation of facts.  Its true that hunter-gatherers tended to be taller and possibly healthier than their early agriculture contemporaries (I am going to assume that Ryan and Jetha do not mean, despite their implications, to compare these bands to modern society).  They may also have lived longer lives, once they hit adulthood, thanks to fewer communicable diseases (though they were still quite disease-ridden, many human-borne diseases do not need large population sizes or farm animal hosts to proliferate).  But, as evolutionary psychologists both authors should be well aware, their sharing ways stemmed more from kinship ties than a poverty of possessions.  Indeed, relations between different bands or even between sufficiently distant relatives within bands were/are quite contentious and frequently violent, much more so than in agricultural societies, whose large populations necessitated the early adaptation of institutions for adjudicating disputes.    Similarly, patriarchy begins with agriculture because political hierarchies begin with the same, and, given our previously demonstrated tendency for male domination, patriarchy becomes the norm.

The population disparity brings up another wrinkle.  Consider: the shift towards agriculture almost uniformly produced surplus foodstores and sizable population growth compared to HG bands.  Either agriculturalists were having more children or they were more able to feed the mouths they naturally produced.  Since I cannot imagine hunter gather bands being less sexually active than agriculturalists (certainly not in the polyamorous utopia the writers envision) then the latter explanation seems correct.  HG bands must have suffered much higher infant mortality rates than early agricultural societies.  They lived a Malthusian existence at the carrying capacity for their environment, were the competition for food, especially at an early age, was intense.

One of the biggest ironies of this book is that it seems at first to be arguing from biological determinism, but its conclusions not only do not flow necessarily from biology but are regularly defeated by more obvious arguments from biological determinism. As one final example, the authors briefly endorse the most biologically bankrupt of the three adaptionist explanations for homosexuality (the male-bonding theory) because it coheres nicely with their sexually promiscuous man theories (the same can be said for their scientifically unsound support for the plasticity of sexual orientation).  Ryan and Jetha regularly make tenuous leaps from biological norms to dubious social explanations and historical reconstructions, consciously avoiding more direct conclusions, in order to confirm their pre-existing biases.  Biology may be destiny, just not the pat way they think it is.

A sidebar: I know have really been getting my Irish up about science writers lately.  I am not quite sure why, but I imagine we will return to the usual programming of something mildly amusing from the internet and overly long articles on video games soon enough.



  1. Hi. Happened upon your unusually thoughtful review of our book via the wonders of GoogleAlerts. Unfortunately, you’ve confused polygamy with omnigamy or more commonly, multi-male/multi-female mating. We don’t argue, as you assert, that humans are naturally polygamous. We argue that humans are naturally promiscuous. It’s very different, and not, as you assert, the mainstream scientific consensus at all, which is that we are, like gorillas, for example, a harem-based, alpha-male species OR long-term pair-bonding, as people like Owen Lovejoy have been arguing forever. Also, not all great apes are polygynous, as you state. In fact, of the six species of great ape, only gorillas are polygynous. Chimps and bonobos are promiscuous (and humans, if you buy our thesis), gibbons monogamous, and orangs dispersed.

    Anyway, I hope you get a copy and give it a read. You obviously are a deep thinker and we’d appreciate hearing your thoughts.


    • Dr. Ryan,

      I am honored that you both read and replied to my disjointed thoughts on your recent book, despite my prejudging it based on a collection of snippets, interviews, reviews, and the Q&A’s you published on Pyschology Today. I really appreciate the comments you left and I would like to address them as best I can.

      As a recent college grad, I suspect my impressions of how widespread the idea of the naturally promiscuous human are strongly colored by the stance of my professors, who treated the issue as simply settled science, and likely assigned textbooks who took a similar stance. My major advisor, for example, was fond of the likely-apocryphal stat that 1-in-20 children are the products of an affair. It is certainly possible, as you and your coauthor argue, that this notion is not as widespread as I was lead to believe. Either way, as I said in my post, the idea that Homo sapiens is a sexually monogomous, pair-bonding species is certainly the conventional wisdom more broadly, so treating your thesis as iconoclastic is not unjustifiable. Further, I would like to thank you for correcting my sloppy use of the word “polygamous.” I was indeed using it as synonymous with “non-monogomous,” which, as you point out, is not necessarily true.

      As for your point in the post below, I was calling into question the social, instead of sexual, organization and behavior of humans as compared to mammals. Though I again made sloppy use of some terminology, I remain more convinced with “most evolutionary psychologists [who] assert that male obsession with controlling female sexual behavior is intrinsic to human nature” compared to you and your coauthor’s theory that these behaviors (and the resultant patriarchy) stem from “economic conditions that arose with farming.” Despite their sexual promiscuity, chimpanzees still display male dominance over females and chimpanzee troops are still organized hierarchically. Males still fight over females and try to prevent other males from mating with females with whom they’ve copulated based on a fairly basic evolutionary calculus: it increases their chances of propogating their genes. I was surprised that the paragraph I cited resorted to a socially-imposed explanation, as these behaviors are an outgrowth of a lot of the physiological adaptations you reference elsewhere. I cited elephant seals as an extreme example of how these evolutionary pressures weigh on mammalian social organization because its the out-there example with which I am most familiar, but more extreme behaviors of male dominance are certainly not unheard in the primate order. Baboons, for example, are known to not only kill rivals’ children, but force females impregnated by others to miscarry so that they might copulate with them sooner. The idea that human male-dominant social organization requires material possessions to propogate thus seems silly to me when a) these traits are so common across much of Mammalia and b) the wealth of the average person does not change perceptibly following the transition to agriculture. Granted, I am still responding to a paragraph from your Q&A articles, so it will be interesting to see what the book itself says on the matter.

      I know my initial post meanders into the realm of the excessively (and not entirely sincerely) hyperbolic dismissal towards the end, so I want to reiterate that I think that ideas discussed in Sex at Dawn sound really interesting and certainly merit a wide audience. So congrats on publication and I look forward to reading the book.

  2. Why is “Nook thoughts” the only “Possibly related post?” I would be very disheartened by that.

  3. P.S. Just read the rest of your piece, in which you lay out whoppers like this:

    “This is all, quite frankly, bullshit. One, the male sexual domination of females and prevention of female infidelity did not begin with farming. It does not even begin with humanity. As we said earlier, most mammals and all great apes are polygynous. They keep harems of females to mate with and violently ward off any males who might try to copulate with their females. We are not even the most egregious offenders. Elephant seals, for example, take huge harems, where one or two dominant males might control nearly the entire female population with the rest receiving none at all.”

    You write in the loud voice of someone who thinks they know what they’re talking about, but in fact, you really don’t know much about apes (see my previous comment). If you want to make biological comparisons, start with the species closest to humans (chimps and bonobos–both promiscuous). Elephant seals?

  4. Hey Chris,
    You raise legitimate questions here concerning male dominance behavior in chimps and other primates, but when you read our book, you’ll see that these behaviors vary depending on the primates in question. It’s true, for example, that despite their promiscuity, male chimps sometimes try to control females sexually. But then on the other hand, the very closely-related bonobos show absolutely none of this behavior. Elephant seals, like gorillas, are not really very relevant at all, as their extreme body size dimorphism clearly indicates a long evolutionary history of a completely different mating system.

    In any case, thanks for your interest in our book. Drop me a line via our website, if you post comments after reading it (or maybe the magic of Google Alerts will remind me). I hope you enjoy the book (and that some of those professors of yours will start assigning it to their classes!).


  5. […] primary school reminds us that water has a ratio of hydrogen to oxygen that is not exactly monogomous.  I wonder if the Lure braintrust devise a well-known diatomic molecule for the bishops to […]

  6. […] Lure has been critical of sophistical evolutionary logic in the past, so when I came across Jesse Bering’s article about the […]

  7. […] all, uncoincidentally, echoes the more sociological (as opposed to biological) criticisms posed, by myself and others, to Savage’s compatriots Drs. Jetha and Ryan about the efficacy of trying to […]

  8. […] it is frustrating when people like Drs. Ryan and Jeffa (Lure interlocutors) advocate polygamy or at least less restrictive monogamy with references to biology and individual […]

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