Book Review: Sex at Dawn by Christopher Ryan and Cacilda Jethá

Not my image.

I’ve wanted to read this book for a while, but it was always at the back burner.  However, a friend recommended this to me and so I quickly read this.  I’ve now read it twice.  Most of it was interesting and the authors present a radical thesis: early humans used to be promiscuous and nonmonogamous, much like our evolutionary cousins, the bonobos.  However, what ruined this lifestyle was agriculture.  They even have a website for more updates and contact info.  I’m glad that I’ve read the book, and I’ll be teaching a few chapters of this to my class.  It’s worth the read for its provocative thesis and their arguments for it.  However, I’m not fully convinced of their justification.  The book breaks up into five parts, but for simplicity, I’ll break it into three parts.

I. Questioning the Standard Narrative

We are relatives to the great apes: chimpanzees, bonobos, gorillas, orangutans, and the “lesser ape” gibbons.  Our closest relatives are the chimps and bonobos.  Chimps and bonobos are the most hypersexual of the great apes.  And since we are closely related to them, we also share this hypersexual tendency as well.  Before agriculture, everything our hunter-gatherer ancestors was shared—including sex.  We can still see this with chimps and bonobos.  In terms of humans, our consumption of pornography and our difficulties with long-term monogamy should give a clue.  Indeed, the authors contend that both humans and bonobos find nonreproductive sex “natural.”  What makes this funny is that “we look to chimps and bonobos for important clues [about our evolutionary development]: language, tool use, political alliances, war, reconciliation, altruism…but when it comes to sex, we prudishly turn away from these models to the distantly related antisocial, low-I.Q. but monogamous gibbon?  Really?” (p. 246)  A huge majority of animals only have reproductive sex.  Humans have recreational sex.  Thus, when the claim suggests that we are like animals.  This isn’t true.  We are far more hornier and have sex much more often then the animals.

The standard narrative is thus: men and women are monogamous to each other, but they secretly try to find other partners.  Thus, there is a sexual contract with an economic game theory where there is a desire to cheat but they don’t because of the risks.  However, sometimes they take the risk and try not to get caught (women are much better at this).  Why?  For the men, it’s to spread his seed and father many children as he can.  His genetic material is spread out.  For women, she wants a relationship with a settled man, but she wants to have a child that is very manly and rugged.  Thus, she sleeps with rugged men, but comes home to the nice guy because this nice guy gives her resources and protection.  Studies have even shown that during her most fertile moments, she makes herself more attractive and finds more rugged men more attractive.  These dark secrets that men and women keep from their spouses seem to make each other miserable.

Another feature of the narrative is that men share their food and resources with the women, and in return, the women gives her sexuality to the men.  So women are trading their sex for stuff.  The authors argue that this narrative didn’t enter into human consciousness until agriculture came about, which was about 10,000 years ago.  Furthermore, there are too many contradictions behind this narrative:

  1. Females are and are not sexual creatures.  Just quoting from the book itself: “[D]espite repeated assurances that women aren’t particularly sexual creatures, in cultures around the world men have gone to extraordinary lengths to control female libido: female genital mutilation, head-to-toe chadors, medieval witch burnings, chastity belts, suffocating corsets, muttered insults about ‘insatiable’ whores, pathologizing, paternalistic medical diagnoses of nymphomania or hysteria, the debilitating scorn heaped on any female who chooses to be generous with her sexuality…all parts of a worldwide campaign to keep the supposedly low-key female libido under control.  Why the electrified high-security razor-wire fence to contain a kitty cat?” (p. 39)
  2. Men and women love each other and mutually exploit each other.  Again, quoting from the book: “Conventional evolutionary theory assures us that all you scheming, gold-digging women reading this are evolved to trick a trusting yet boring guy into marrying you, only to then spray on a bunch of perfume and run down to the local singles club to try and get pregnant by some unshaven Neanderthal as soon as hubby falls asleep on the couch.  How could you?  But before male readers start feeling superior, remember that according to the same narrative, you evolved to woo and marry some innocent young beauty with empty promises of undying love, fake Rolex prominent on your wrist, get her pregnant ASAP, then start “working late” with as many secretaries as you can manage.  Nothing to be proud of, mister” (p. 58).
  3. Females have hidden fertility in order to reassure and confuse males.  With other animals, they go into heat and the male sex can tell that it is time for sex.  With humans, however, females have concealed ovulation and they can have sex any time.  This is also true of bonobos.  Recall that part of the narrative is that women aren’t interested in sex.  If so, then why did she evolve to have this sexual capacity?  Helen Fisher’s explanation is that since her fertility was hidden, he would have to stick around just to make sure that her progeny was also his, making sure that no other males mated with her.  However, Sara Hrdy suggests that this sexual feature wasn’t to reassure males, but to confuse them.  The female would have sex with many males so that none of them could be sure which one was the true parent.  Fisher’s model may work but only if the male was interested in having sex with one female, which already contradicts the standard model.
  4. One should be jealous of any infidelity because the parents don’t share DNA with the offspring, yet any infidelity with anybody related to the parents is off limits too.  The standard narrative suggests that jealousy would come about if there was any infidelity.  This is because it has an evolutionary advantage.  If there is any infidelity, then the offspring don’t share the same DNA with the original parents.  Thus, according to the standard narrative, jealously is a natural thing.  However, “if it’s a question of genes, a man should be far less concerned about his wife having sex with his brothers–who share half his genes–than with unrelated males.  Gentlemen, would you be far less upset to find your wife in bed with your brother than with a total stranger?  Ladies, would you prefer your husband have an affair with your sister?  Didn’t think so” (p. 141).  Indeed, I recall Shakespeare’s Hamlet where Hamlet’s father died and so his uncle married his mother, which no one was bothered by.  Of course, Hamlet was bothered by his uncle, but not because it was his uncle being with his mother, but because of the intricacies of his uncle killing his father.  Even within 600 years, relations of one parent marrying a relative of the spouse was normal, whereas by today’s standards, it’s not.  This suggests that jealously isn’t natural, but cultural.

Not only is it rationally unsound, but there are empirical examples to suggest that the standard narrative is false.  Many tribes and cultures have a promiscuous attitude about sex where jealousy isn’t there.  Indeed, the men in these cultures are more bound to one another because of a shared paternity.  There are some cultures where not only is adultery mandatory, but one has a moral duty to respond to these sexual advances, whether one is married or not.  There is another tribe where the see the growth of the fetus as accumulated semen from many men.  The more men the women has sex with, the stronger the fetus will be.  The Romans celebrated a marriage with a wedding orgy where the husband’s friends has sex with the bride.  The Mosuo don’t have a language for “husband” or “wife.”  Indeed, we consider any infidelity with shame.  The Mosuo consider fidelity with shame.  Vows of fidelity is considered inappropriate, so is jealousy.

Speaking of jealousy, this is not a natural emotion; rather it’s cultural.  We learn how to express emotions and when it’s proper to express them and what should be expressed.  It’s a social phenomenon.  Indeed, jealousy toward a possible sexual partner has been a major obsession.  When it comes to having many children or many things, we find no problem.  “We seem to manage [love] with parental love…, love of books, of food, of wine…, love of composers, poets, holiday beaches, friends…why is erotic love the one exception that everybody instantly acknowledges without even thinking about it?” (p. 148)

Thus, the standard narrative already claims that both males and females deceive each other and that we are by nature liars and cheaters to our partners.  This, says the authors, is a mistaken narrative and should be challenged.  This is how things are currently but not what it was back then.  Indeed, to project any sort of current experiences and cultural proclivities into our prehistory is what the authors call “Flintstonization.”

Not my image.

The other assumption is a neo-Hobbesian account of human nature: everyone is out for themselves and any sort of shared cooperation makes one the loser in any economic game theory.  After all, to have the offspring survive assumes this neo-Hobbesian outlook because the offspring survives through assured paternity and resources for the offspring.  The father knows that it’s his offspring; the mother gains protection and resources from the father.

Again, the authors contend that this assumption is a mistake.  We are assuming that our current conception of what the family is all about is a universal aspect of human nature.  Again, this is Flintstonization.  What if instead of each this every-man-for-himself narrative, there was a general sharing?  What if there was a group-wide sharing, which would offer more protection and have a much more effective way to mitigate the risks?  Indeed, what if paternity uncertainty actually helped the child, because all the men would share in parenting instead of just one?  Indeed, egalitarianism is found in nearly all hunter-gatherers.  This wasn’t because it was moral or noble, but it was because this generalized sharing was the most effective way to survive.  Thus, “the standard narrative is exposed as contemporary moralistic bias packaged to look like science and then projected upon the distant screen of prehistory, rationalizing the present while obscuring the past” (p. 149).

Women actually had as much access to food, protection, and social support as men did.  But then came the advent of agriculture and then women had to barter their reproductive capacity to have access to resources and protection.  Now, all of the sudden, women were seen as the lesser of the sexes.

The authors contend that we are mostly related to chimps and bonobos.  Indeed, we are equidistant from both of them.  So how to chimps and bonobos look at sex?  Chimps use violence to get sex; bonobos use sex to avoid violence.  Chimps have a very aggressive and hierarchical order where the dominant males take control of the food.  Thus, there’s much more aggression, warfare, rape, infanticide, and a Hobbesian type of nature.  With bonobos, it’s female centered.  There has never been a murder, rape, or infanticide since people have been studying bonobos.

Now when it comes to sexuality, humans are closer to bonobos.  Bonobos have sex face to face, they tongue kiss, they can look into each other’s eyes.

OBJECTION: How do you know?  Throughout the book where the authors mention how agriculture messed things up, they don’t offer much linkage.  There are nice graphs and quotes, but nothing concrete in terms of evidence.  They seem to extrapolating a lot by suggesting that by being related to the bonobos, we must be life them too.  If we are relatives to both chimps and bonobos, and chimps are more like Hobbesian creatures whereas bonobos are more like Rousseauian creatures, why lump humans closer to the bonobos, at least in terms of their sexuality?  Overall, I see the argument as such:
1.  We are related to species x.
2.  Species x does activity S.
3.  Therefore, We are more inclined to do S.

II. The Anatomical Evidence

It is here that the authors give 12 bits of evidence:

  1. Body-size dimorphism
  2. Sperm competition
  3. Testicle size
  4. Penis size
  5. Pornographic visualization
  6. Shape of the penis creates a vacuum in the female’s reproductive tract
  7. Growing infertility among males
  8. Time length for each sex to reach orgasm
  9. Female Copulatory Vocalization
  10. Genital Echo Theory
  11. Female’s body can reject sperm, even if the female is attracted to the male
  12. The structure of the cervix

With body-size dimorphism, it has been correlated with male competition with mating.  The bigger the dimorphism, the stronger the competition.  In the great apes, gorillas have the strongest dimorphism (males are about twice the size as females) whereas gibbons are virtually identical in size.  For humans, males are about 10-20% bigger.  Oh, and guess who else has a similar body-size dimorphism?  That’s right, our promiscuous cousins chimps and bonobos.

With sperm competition, if there is sperm of more than one male in the reproductive tract of the female, then the spermatoza themselves compete within the vaginal tract to fertilize the ovum.  Part of the sperm competition is that the first spurt contains chemicals to protect any other chemical attack such as chemicals from other mens’ sperm.  The final spurts contain a spermicidal substance to slow down later sperm that might come in.  Along with this, studies have shown that a man’s sperm production increases when he hasn’t seen his partner in a few days, regardless if he’s ejaculated during the absence.  Thus, that absence could’ve been an opportunity for the partner to see someone else.  Nature has equipped men to increase the sperm production just in case the partner was seeing someone else.

With testicle size, “[m]ales apes living in multimale social groups (such as chimps, bonobos, and humans) have larger testes, housed in an external scrotum, mature later than females, and produce larger volumes of ejaculate containing greater concentrations of sperm cells than primates in which females normally mate with only one male per cycle (such as gorillas, gibbons, and orangutans).  The theory behind this is that the more one has sex, the larger the testes will be.  And if there are several males with a lot of sperm competition to one ovulating female, they’ll need even bigger testes.  For monogamous apes (e.g. gorillas, orangutans, gibbons), the males have smaller testes.  This also happens with birds, butterflies, reptiles, and fish.  We have more sperm-producing tissue than any monogamous or even any polygynous primate would need.  It’s as if we were built to be promiscuous.

With penis size, it’s also correlated with promiscuity.  To have the sperm be delivered to the ovum, the longer and thicker the penis needs to be.  Indeed, out of all the great apes, humans have the longest and thickest penises.  Gorillas, since they keep a harem of females only have an inch long penis with testes the size of kidney beans, which are tucked up inside the body.  The promiscuous bonobo has a three inch penis with testicles the size of chicken eggs.  Humans are somewhere in between in terms of testicle size.  To have an illustration of this, go here.

OBJECTION: I can understand the length of the penis, but why thickness?  How is that an evolutionary advantage, especially with being promiscuous?  Unfortunately, the authors don’t talk about it.  However, this could just be a side-note.

With pornography, heterosexual men get really turned on where there are groups of guys having sex with one women.  Why?  The authors suggest it’s because this is the best environment where sperm competition is at play.  I was skeptical at first, but there is empirical studies that suggest multiple-men-one-girl porn is far more popular than one-man-multiple-women porn.

The shape of the penis is to create a vacuum in female’s reproductive tract, this vacuum pulls out any previous deposited semen away.  It’s as if the penis was a plunger to pull out other fluids, including other sperm.  And as soon as the man ejaculates, the head of the penis shrinks so that the suction of the vacuum isn’t in effect.

With growing infertility among males, infertility can be passed on.  If you have an infertile man vs. a fertile man, no doubt the fertile man is going to win in the sperm competition.  Infertile men wouldn’t have fathered any children under promiscuous species.  But because our culture has been brought up with monogamy as the norm, there are no fertile men to win out the infertile men; there’s no sperm competition.  Eventually, when the infertile men does impregnate a women, genes with reduced fertility won’t be reduced from the gene pool.  Thus, “sexual monogamy permits fertility-reducing mutations to proliferate, causing testicular diminishments that would never have lasted among our nonmonogamous ancestors” (p. 239).  In other words, monogamy has made males’s sperm weaker.  Infertility seems to be a growing phenomenon as well.  It could be that sexual monogamy may be a significant factor in contemporary infertility that we’re seeing today.  More than that, imposed monogamy may help explain why men’s testicle size has gotten smaller than the chimp and the bonobos.  In short, “[s]exual monogamy itself may be shrinking men’s balls” (p. 240).  As a related issue, monogamy seems to have drained away testosterone.  Married men show lower levels of testosterone than single men.  Fathers of young children have even less.

With time length for each sex to reach orgasm, it seems odd that if we are truly monogamous by nature, then why is it that men generally reach orgasm quicker than females do?  Yes, there are “mixed strategies,” but this gets us back to the standard narrative.  Instead, there is one other possible scenario on why humans evolved like this. It seems that when a man ejaculates, he’s done but the woman is just getting started.  Thus, another man can enter the picture and the woman can presume toward orgasm and more sperm, hence having sperm competition.  Indeed, female humans aren’t the only species to have orgasms.  Gibbons, the monogamous ape, do not have obvious signs of female orgasms.  Indeed, “[i]t’s worth repeating that primate species with orgasmic females tend to be promiscuous” (p. 268).  Now listen to that: orgasms are clues that we were promiscuous.

With female copulatory vocalization, when it comes to hearing people having sex, it’s typically the female that we hear.  Why is that?  If sex is considered a private matter, why do we hear the moans of other people having sex (especially the female)?  The authors contend that it doesn’t make sense for the female to call attention to herself during sex.  Other primates, do the same and this calls other males to come forward.  Hence, this call is a potential invitation for other males to come to this female.  It’s as if the female is saying, “Hey, I’m having sex right now.  Anyone who can hear me can join in?”  Thus provoking sperm competition.  These calls are hardly in monogamous or polygynous species.

OBJECTION:  I’m extremely skeptical with this bit of evidence.  It seems that a woman’s call during sex isn’t meant for other people to hear; rather, it’s for her partner.  The call is a way for the man to get aroused quicker and easier so that he can ejaculate.  The side-effect of this call is that other people hear it.  The authors seems to have this backwards.  Moreover, bonobos and chimps function in a hierarchical relationship where there are alpha males and alpha females.  Suppose a beta female was with an alpha male.  Couldn’t the call be more about bragging rather than calling more males to come forward?

With genital echo theory, it seems odd that female humans have breasts as soon as they hit puberty.  Other primates don’t develop breasts unless they’re nursing.  It seems that having breasts constantly would be a huge evolutionary disadvantage.  So why have them?  Going back a bit, early primates walked on all fours usually and their buttocks were the spot that aroused males.  However, when humans started walking upright, they couldn’t see the full range of the buttocks that well, so they needed to look at something else that resembled buttocks.  Genital echo theory suggests that as soon humans started walking upright, females developed breasts because the cleavage resembles the buttocks. This is why males are more attracted to a bigger bust, even though breast feeding has nothing to do with breast size.  Sounds good.  But why always?  Recall that human females have a hidden fertility.  Thus, “[a]s the human female is potentially always sexually receptive, her breasts are more or less always swollen, from sexual maturity on” (p. 261).

[T]he female’s body can reject sperm, even if the female is attracted to the male, the female may not be the best judge of the best potential contributer to her offspring.  This is why 35% of females reject sperm by perceiving them as antigens and the female can produce anti-sperm leucocytes.  At the same time, part of the women’s body can assist other sperm.  This suggests that the female reproductive system is capable of making some sort of judgment based on the chemical signature of men’s sperm.  Not every ‘high quality’ male would be a good match for any specific woman–even on a purely biological level.  Because of the complexities of how the two sets of parental DNA interact in fertilization, a man who appears to be of superior mate value (square jaw, symmetrical body, good job, firm handshake, Platinum AMEX card) may in fact be a poor genetic match for a particular woman.  So, a woman (and ultimately, her child) may benefit by ‘sampling many males’ and letting her body decide whose sperm fertilizes her.  Her body, in other words, might be better informed than her conscious mind.

Thus, paternity wasn’t dictated by external factors; rather, it was determined by the inner world of the female reproductive tract and every women has certain mechanisms to choose a potential father at the cellular level.  It’s as if the cervix is a filtering device for sperm, which suggests that it had evolved from a promiscuous ancestry.

III. The Upshot

Usually, the end of the book has an extremely generalized take on what we now know and what can we do from here perspective.  The authors contend that the standard narrative has made the sexes mutually exploit each other where they are designed to make each other miserable, predators to each other’s interests.  Instead, “[t]he assertion that human beings are naturally monogamous is not just a lie; it’s a lie most Western societies insist we keep telling each other” (p. 270).  More evidence suggests that women’s sexuality is much more malleable than men, and that both sexes seem to have dissatisfaction more often once they are within a monogamous relationship.  There may be a correlation with the increase of depression and violence lately, especially in the United States.  So what are you options if you hold on to monogamy?

  1. Cheat and try not to get caught.  This may be the worst option, however, because, well, it’s simply lying.
  2. Stick with it but resort to porn and anti-depressants.  Yet, with anti-depressants, one of the side effects is a decrease of libido so it seems to feed into this cycle.
  3. Serial monogamy.  This seems to be the most popular solution, but this seems like a cop-out.

So what to do?  Unfortunately, the authors don’t offer any positive advice, except for a generic “follow what you want to do and be true to yourself” sort of philosophy.  One cannot force people into a certain expectation, especially if it’s something that is not essential to us.  “What isn’t debatable is that conventional marriage is a full-blown disaster for millions of men, women, and children right now.  Conventional till-death-(or infidelity, or boredom)-do-us-part marriage is a failure.  Emotionally, economically, psychologically, and sexually, it just doesn’t work over the long term for too many couples…couples with “open marriages” generally rate their overall satisfaction (with both their relationship and with life in general) significantly higher than those in conventional marriages” (p. 308-310).

So what can I say with this book?  We need to understand what it means to have a fluidity of sexual fidelity, perhaps to what Dan Savage has called for monogamish.  Or at least accept the idea of nonmonogamy as a genuine lifestyle for people who accept it.

My questions have to do with whether Ryan and Jethá are right.  They’re specialties are in psychology and medicine.  Evolutioary psychology can’t really be varified, and so there is a lot of speculation.  The questions I have are whether the biology and evolution is correct in this book.  Since I’m not proficient in either one of them, I can’t say for sure.  There is another book that questions the whole argument of this book, which I’ll read and review later for this blog.

An evolutionary biologist has also questioned the premises of this book by stating that the evidence that Ryan and Jethá make is weak, and that they have left out some counterevidence for their claims such as the !Kung and Canela tribes.  Moreover, even the most liberal sexual societies and tribes still experience jealousy.  Even in these tribes, the word “promiscuous” still has a negative connotation, and is usually portrayed toward women.  The Inuit tribes to exchange wives, but without the wives say.

Moreover, the sexual dimorphism that Ryan and Jethá claim is misplaced.  If you ignore the fat, the sexes of humans are actually similar to the gorilla, a polygynous species.  And they wrongly conclude about testes size in a paper that they refer to.  Indeed, no evolutionary scientist agrees with “the standard narrative” that Ryan and Jethá portray.  From the article itself:

Men and women are genetic competitors with different available routes to reproductive success (another lamentable element of the “standard narrative,” e.g., p. 49, 58, 270). There is considerable cross-cultural variation concerning such things as extramarital sex, premarital sexual freedom, strength of marital bonds, and degree of female reproductive autonomy. And sperm competition likely posed a selective pressure on ancestral males (Shackelford, Pound, and Goetz, 2005). But to argue that the evidence points to the level of promiscuity argued by Ryan and Jethá is to turn a blind eye to disconfirming, inconvenient facts, while indulging in quite a bit of fantasizing. 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, 332).

It looks like evolution is right that we may not be strictly one-partner-only-for-a-life monogamous at heart, but neither are we promiscuous at heart either.  I won’t go into more details about Ellsworth article since this is meant for a book review.  However, I will read Sex at Dusk which is a full rebuttal to Sex at Dawn and I will do a book review sometime in the future.  Ryan and Jethá argue against a neo-Hobbesian view of human nature, but by doing so, they seem to promote a neo-Russeauian paleofantasy.

Would I recommend this book?  Sure, but not for the evolutionary data which may be factually inaccurate.  I would recommend it because the authors bring out a new theme of what sort of relationships we can have, what we could have, or what we would have if we are more honest with ourselves.  They don’t propose a nonmonogamous lifestyle out front, but they do suggest that maybe, being monogamous is something that isn’t programmed in us, but rather a cultural artifact.  I believe that is something worth thinking about.

About shaunmiller

I have just completed a visiting position as an assistant professor at Dalhousie University. My ideas are not associated with my employer; they are expressions of my own thoughts and ideas. Some of them are just musings while others could be serious discussions that could turn into a bigger project. Besides philosophy, I enjoy martial arts (Kuk Sool Won), playing my violin, enjoying coffee around town, and experimenting with new food.
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1 Response to Book Review: Sex at Dawn by Christopher Ryan and Cacilda Jethá

  1. Pingback: Book Review: What Do Women Want? by Daniel Bergner | Shaun Miller's Ideas

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