Evolutionary psychology, sexual dimorphism, and ideology

November 26, 2014 • 8:41 am

(Note to non-biologists: “sexual dimorphsim” refers to any trait or behavior that differs between the sexes, like the ornamented tail of the male peacock, the brighter color of the male painted bunting—and of many birds—and the bower-building behavior of male but not female bowerbirds.)

There are some science-friendly folk (including atheists) who simply dismiss the entire field of evolutionary psychology in humans, saying that its theoretical foundations are weak or nonexistent. I’ve always replied that that claim is bunk, for its “theoretical foundations” are simply the claim that our brains and behaviors, like our bodies, show features reflecting evolution in our ancestors. While some evolutionary psychology studies are weak, and I’ve been a critic of them, the discipline as a whole is growing in rigor and should certainly not be dismissed in toto.

Those who still do, though, should answer this question:

Why are human males, on average, bigger and stronger than females?

This is true not only in our species, but in our three closest relatives: chimpanzees, orangutans, and gorillas, as well as in most primates (there are a few exceptions, like gibbons).

The most obvious answer is male-male competition: our male ancestors competed with each other for females, and bigger bodies made for more successful competitors. That size difference can be useful in both direct physical competition (as in mule deer!) or simply in dominance, like establishing territories, or even in showing you have “better genes”.  (In fact, mate choice based on size may still operate in humans if females prefer bigger or taller males as opposed to smaller ones like me.) And if males competed for females, that reflects a difference between the sexes in reproductive strategy—that is, in behavior.  Finally, if the physical result of this behavioral difference remains in our species, why would the behavioral difference itself not remain as well, with males competing for female attention? Various psychological and sociological studies in fact show this to be the case in modern humans.

The theoretical underpinnings of the behavioral difference have long been understood and supported with data: the difference in parental investment that usually makes males less discriminatory in choosing mates than are females (sperm is cheap; pregnancy and suckling expensive). The theory also makes substantiated predictions. One of them is this: in those species (both primate and nonprimate) in which males have a larger variation among individuals in reproductive success (i.e., those having “harems” versus those that are more monogamous), the species having more variation (more “polygynous”) should show a bigger size difference between males and females. For in those species in which a male can garner lots of females, leaving a lot of males as chaste bachelors, there will be stronger selection for males be larger. And that is what we find.

So those who dismiss evolutionary psychology wholesale must still explain why in every human society males are on average larger than females. (The answer probably doesn’t involve an ecological difference between the sexes in our ancestors, as such ecological differences don’t seem to exist in our closest primate relatives.) And if you admit that those differences in body size reflect ancient evolution, why do opponents of evo-psych claim that the differences in behavior that produced the physical dimorphism are no longer with us?

This is not to justify any sex differences in behavior as “right” or “moral.” That is the naturalistic fallacy.  But the left-wing opposition to evolutionary psychology as a valid discipline in principle, especially when it involves differences in sexual behaviorseems to me based more on ideology than on biology. Ideologues cannot allow any possibility that males and females behave differently because of their evolution. Such people think that this would buttress the view that one sex would be “better” than the other.

But what evolved does not mean what’s right or what’s inevitable; and everybody with two neurons to rub together knows that. Humans may have evolved to be xenophobic and even violent towards members of “outgroups,” but we have the ability through culture and learning to overcome such a tendency. And, in fact, overcoming xenophobia happens to be both more useful and more ethical in a world of wide interactions between people and nations—interactions much different from those experienced by the small social groups of our African ancestors.

Biology is not ideology, but neither should ideology dictate biology.


295 thoughts on “Evolutionary psychology, sexual dimorphism, and ideology

    1. Indeed, and by coincidence I started reading some of the comments from the bottom and they seem to have taken a more serious if well deserved approach, but here I am going to just ask, tongue in check: is this then the reason why my wife preferred me over other dudes, since I’m 1.84m tall (about 6’1″) and she is 1.60m (5’3″)? And perhaps the same reason why she panics when seeing a spider? Is she “less evolved”?

      1. My wife has never deviated from saying I’m her choice because I am tall. At least that was the minimum requirement. We have a grandson now, and she is a bit miffed by reversion to the mean.

        Possibly off-topic aside. I once had a co-worker, female and gay. She was one of the tiniest people I’ve met. I asked hey why she drove a certain huge SUV. She said, because they didn’t make a bigger one.

        I interpret this to mean that women feel safer when protected by a big man. I suspect that might offend some people, but I’m just reporting.

        1. As a smaller woman (though not really all that small) I think it’s a bit of an advantage. Men can yell at me and since they could all beat my ass if they wanted to, I’m not really more intimidated by big men.

          Once, when I told a male friend about how to alpha males were trying to compete with each other in a meeting and basically talked over everyone in order to do so, derailing the meeting, he told me I should’ve stood on a chair and added, “I would’ve”. 🙂

        2. I think there is something to that feeling of being protected by a big man, or at least not being bigger than your man, which has never been a problem for me ’cause I’m pretty small.

          1. Have to admit I like big men. I’m 5’3″ and small-boned. I spent many very happy years with a man who’s 6’5″ and big with it. His size attracted me, but it was his mind, intellect, and sense of humour that kept us together.

            I was told by doctors though that if we had children I’d have to have a caesarean. In different times having his children might have killed me I suppose.

          2. You’re one of those women the tall girls would have told you to “get away from our men!” 🙂

          3. When I was young I had a very obvious crush on a tall (over 6ft) man, and I was 5ft nothing at the time (bit shorter now). A lot of older folks kept telling me I needed to find someone closer to my own height. It took me a long time to figure out what they were hinting at. I couldn’t see a problem.

        3. I asked hey why she drove a certain huge SUV. She said, because they didn’t make a bigger one.

          In the words of Cynthia Payne (or the script-writer for her “auto-“biography), “BCSD.” Which originally stood for “Big Car, Small Dick.” But Madame Syn made more money from BDSM than Sapphism, though I’m sure she’d have not had any compunction about servicing your lady friend. For a suitable fee. In Diner’s Card vouchers.

      2. ‘Is she “less evolved”‘

        Than you, for instance?

        If 1) she her behavior is different than yours 2) some of this difference is due to difference in genes and 3) those difference in genes is due to the effects of natural selection, the she is highly evolved. Same as you, I would bet.

  1. Why are human males, on average, bigger and stronger than females?

    …The most obvious answer is male-male competition

    Huh. I thought the most obvious answer was anabolic steroid use. Take a woman, and inject her with small amounts of steroids every day from the age of 12 until she’s 20, and I bet you’ll get a woman the same size and strength as the average man.

    IOW it’s what Gould called a spandrel. Males use testosterone to produce sperm (or at least, the two are related). Side effects of having testosterone in our system include making us slightly bigger, stronger, and also it cuts down on our life span. No sexual dimorphism hyopthesis or evolutionary psychology hypothesis is really needed here.

    1. I should amend my post: I don’t question the possible link between size and competitive advantage in many species. But in humans the sexual dimorphism is so slight (8% difference in height, at least in the US), that it doesn’t make sense to me to try and come up with an additional explanation for it, besides the obvious ‘side effect of production of sex hormones necessary for male reproduction’.

      1. I don’t see the dimorphism as very slight at all. The difference in height is just the start. Distribution and amount of muscle makes men look intimidating. Male shoulder width, beards and body hair it seems to me are consistent with an aggressive display meant to make other males think twice.

        1. I agree – I’m a small but strong female and really small men could easily kick my ass due to how much stronger they are because of muscles that I couldn’t ever have unless I was doping with hormones.

          Further, it makes sense that the sexual dimorphism when it comes to size among males and females would not be incredibly exaggerated because mating would be a nightmare (I’m thinking mostly for the woman but that’s just my female perspective).

          1. I’m a small but strong female and really small men could easily kick my ass due to how much stronger they are

            My quiz-partner’s missus has recently gained a black eye (or something) in some Brazilian martial art whose name I forget, but translates into English approximately as “kicking him in the head until he cries”. She’s not exactly big-boned either.
            Get lessons.
            When she tells me that “it ain’t what you got, it’s how you use it to make them cry”, I feel disinclined to argue. Particularly since she normally has a foot inches from my nose at the time. I do hate spilling my beer.

        2. I don’t see the dimorphism as very slight at all. The difference in height is just the start.

          Compared to the examples typically given from other species, it’s slight. Take the white-tail deer, for example (just because Jerry just put pictures of them here). The size difference by weight is 50%. That’s 2-3 times the as big a dimorphism as in humans, where the weight difference is more like 18%. If humans were as dimorphic as deer, the average male would be 240 pounds.

          And in many other species where we posit sexual dimorphism as a strategy, it’s even bigger than that. In sea lions its more like 50% by length and 300% by weight. That would be the equivalent of the average human male being 400 pounds and about 8 feet tall.

          Our dimporhism is both relatively tiny (even if it’s significant when you’re talking about person-on-person individual combat), and adequately explained by daily steroid “use”).

          1. “Our dimporhism is both relatively tiny (even if it’s significant when you’re talking about person-on-person individual combat)… “.

            Person-to-Person combat, or the threat of it only requires enough size to intimidate. The limitation is in energy expenditure to add muscle and perhaps aggressive emotions. This limit will naturally be species specific. And, for humans it seems that balance is struck at about a 15% mass differential.
            You walk into a bar and see a hot chick seated two seats away from a, smallish, somewhat mousy man. All 6′ 2” of you have to decide whether to seat your 220 lb mass next to the winsome lass, or to find something at a bit of a safe distance. The rest is history…

          2. http://www.putslab.psu.edu/pdfs/puts_10_beautybeast.pdf

            Beauty and the beast: mechanisms of sexual selection in humans

            From page 5/161
            “All of these types of evidence support the prediction that male contests have been important in human evolution. Men
            are larger, stronger, faster, and more physically aggressive than women, and the degree of sexual dimorphism in these
            traits rivals that of species with intense male contests. The relatively modest 8% stature dimorphism in humans (Gaulin & Boster, 1985) and a difference of about 15–20% in body
            mass (Mayhew & Salm, 1990) might suggest that male contests are reduced compared with our closest relatives. However, human sex differences in size underestimate sex
            differences in the traits most relevant to contests. This is partly because women are unique among primates in having
            copious fat stores (Pond & Mattacks, 1987), perhaps for building the large, fatty brains of human offspring (Lassek & Gaulin, 2008), and as sexual ornamentation (see below). When fat-free mass is considered, men are 40% heavier (Lassek & Gaulin, 2009; Mayhew & Salm, 1990) and have
            60% more total lean muscle mass than women. Men have 80% greater arm muscle mass and 50% more lower body muscle mass (Abe, Kearns, & Fukunaga, 2003). Lassek and Gaulin (2009) note that the sex difference in upper-body
            muscle mass in humans is similar to the sex difference in fatfree mass in gorillas (Zihlman & MacFarland, 2000), the most sexually dimorphic of all living primates.

            These differences in muscularity translate into large differences in strength and speed. Men have about 90% greater upper-body strength, a difference of approximately three standard deviations (Abe et al., 2003; Lassek & Gaulin,
            2009). The average man is stronger than 99.9% of women (Lassek & Gaulin, 2009). Men also have about 65% greater lower body strength (Lassek & Gaulin, 2009; Mayhew & Salm, 1990), over 45% higher vertical leap, and over 22%
            faster sprint times (Mayhew & Salm, 1990). Contrary to earlier claims, sex differences in anaerobic sprint speeds are not narrowing (Cheuvront, Carter, Deruisseau, & Moffatt,
            2005; Seiler, De Koning, & Foster, 2007).”

            It’s an interesting article well worth a read.

      2. There are plenty of species in which males (who still, of course, produce sperm) are smaller than females. This is common in birds and fishes.

        I think you’ve got it backwards.

        1. Gotta look at the evolutionary ecology. Relative sizes relate to ecological roles, social ecology, and information (including good genes) signaled in courtship. Pat answers are usually wrong.

      3. I don’t think height is a good, or sufficient, metric to judge dimorphism. For instance, height and volume scale differently.

        The average difference of body mass of males vs females is significantly higher than 8%. From one source of average body masses from several countries, male body mass was overall just over 20% higher than female body mass.

        In addition to that males on average have significantly lower body fat than females, meaning that, on average, more of the males body weight is muscle compared to females.

        Some personal observations regarding strength. There have been periods of time where my wife and I have trained together until we have both reached a peak and leveled out. We have months of meticulous records of work outs from most of those periods and have played with the data several times just out of curiosity. I am about 5’8″ and my wife is about 5’6″. On major lifts, lifts which engage primary muscle groups, such as squats, dead lift, bench press, military press, I was capable of lifting between 2 and 3.5 times more than she was.

        Some other interesting things. That comparison is of heavy workouts, higher weights, low reps, long rest periods. On endurance work outs, lighter weights, high reps, no more than 60 second rests, the strength differences were significantly less. Also, on some minor lifts, lifts that focus on individual, smaller muscle groups, she was nearly as strong as I. For example calf raises. I swear, she must have been cheating on those.

        1. You could squat or deadlift that much more than your wife?

          So if a young, well-trained 5’6″ female can squat about 100 kilos (not an unreasonable assumption), you are saying that you could squat at a minimum 200 kilos or 440lbs in old money?

          Not out of the realm of possibility, especially if you compete, but I have to say that I can count on one hand the number of times I’ve seen men squat more than 405lbs properly in a commercial gym. Or even three wheels for that matter. And for a guy that is most likely under 200lbs, your lifts are very impressive.

          1. Both of us were / are pretty decent, at least when we are in condition. I couldn’t agree more about squats. It is a rarity to see someone do proper squats. At her peak my wife’s workout weight for a heavy workout was 185 lbs. Mine was 385 on an okay day, 405 on a good day. Typically 6 or 7 reps per set, hips below the knees. When I was in my mid 30’s I could pretty reliably go 485 for a single lift and weighed 180-185 lbs, depending on my home-made chocolate chip cookie habit. Even now my regular work out weight is 315, and I weigh about the same. 185 that is. Lately, my lower back has become a limiting factor in many things.

            But the biggest difference between my wife and I was on leg press. I think there must have been a mental aspect to it. Lowering hundreds of pounds onto yourself, squishing yourself, can be uncomfortable mentally.

          2. I loved the leg presses when I did them. I think it didn’t bother me because I have insanely flexible hips from doing ballet while I was growing. If it squishes me, it won’t really hurt.

          3. I can see how that would be helpful.

            I think also that many people never push there limits enough to experience that they can make the lift even when it feels like they can’t. But that could just be me. Pretty much any time I am making even a moderately heavy lift, it feels very heavy and part of me is thinking “shit, this doesn’t feel possible.” The only reason I go ahead and do it is because I have past experience that even when it feels like that, I can still do it.

            And after a while you learn that how you “feel” is not a good way to predict performance. Many of my best days have been when I felt at my worst, and vice versa.

          4. That’s one nice thing about bodyweight exercises. The failure modes are must less dramatic.

            Do a one-leg pistol squat and the worst that’s going to happen is that you won’t have the strength to get back up with the single leg and you’ll have to just sit on the floor. Do a two-leged squat with your body’s weight on the weights…and that much weight is understandably going to make anybody nervous, at least as you approach your repetition limit. But it’s the same force on the muscles in either case.

            (And if, as in your case, you need even more force than that, start by adding pauses of increasing length at the bottom of the movement, or switch legs at the bottom and add an hop at the top.)

            Same sort of thing applies to other movements. Not many people have the strength to do one-armed pushups with feet elevated, let alone with pauses at the bottom. Doing bench presses with comparable free weights is absolutely going to require spotters and still involve fear of being crushed (whether justified or not), but the pushups you can do without worry alone at home without any equipment.


          5. You can achieve great results with body weight exercises and isometric exercises. And you can do them just about anywhere with no specialized equipment. But you can’t achieve the same level of strength as you could via weight training. The pause technique you describe is also a standard technique in weight training.

            It just depends on what your goals & preferences are. Weight training may be more dangerous, but really, it is not dangerous in general terms. And, I like that kind of fear, within certain limits.

          6. Oh, certainly; there shouldn’t be any more danger involved in weight training than there is in any other sport.

            But there’s certainly at least the impression of danger of holding some ludicrous amount of metal over your head, just as there’s going to be climbing up the face of a cliff or the like.

            If you’re a bit of an adrenaline junkie, that can certainly be a good thing…but I’d wager that, for most people, that’s a reason to avoid such high-intensity training in the first place. Which is a damned shame, because it’s far and away the most effective path to physical fitness.

            Thus, bodyweight: similar gains without even the perception of danger, plus no need for equipment — and, therefore, elimination of pretty much all the excuses people use to not do that sort of exercise.

            Don’t have time to go to the gym? Don’t want to buy lots of equipment you don’t have the space to store? Don’t want to be ogled by strangers when you just want to get some exercise? No worries; wherever you are right now, you’ve got more than enough gear for as intense of an ass-kicking workout as you might want.

            As the man puts it, You Are Your Own Gym.


          7. Well…barring injury or the like, and unless you make an awful lot of money as an heroin chic runway model, there isn’t a person alive who wouldn’t benefit significantly from regular strength building exercises.

            Only a very few will become elites who can compete in the Olympics for strength competitions or the like, but that’s not surprising…nor exactly relevant. Everybody benefits from education, too, even though only a few go on to be top-level scientists or authors or what-not.

            …besides, life is much more fun when you’re strong and healthy than weak and sick….


          8. Yeah, I bulk up easily. I’m a big fan of high reps, low weights. Plus, doing regular things that get you fit. I think walking is an overlooked exercise. Keeping your legs strong is important. Sadly, it is also important for keep your bum on shape which includes squats, which I hate.

          9. Walking is a superlative activity, something that everybody should do and almost everybody should do more of. It’s not sufficient exercise in and of itself, but it’s definitely essential.

            And no treadmills! Get out there in the real world, ideally a park but at least the local neighborhood. Uneven terrain is going to make for far superior exercise, and walking is at least as important for the mind as it is for the body. Staring at the same patch of wall (or a TV) for an extended period of time isn’t going to do you any good, but taking in the sights and sounds and smells of your environment will.

            (Not that it’d occur to me that you, Diana, would do the treadmill thing…but far too many other people have wasted good money on those blasted contraptions. They have a place in the physical therapist’s repertoire, especially when coupled with a suspension harness, as well as in the cardiologist’s office, and that’s it.)


          10. I actually do a treadmill work out – interval training for 20-30 minutes. As much as I like walking outdoors, I live in the country and it can be perilous – also it’s dangerously cold in the winter.

            Now that I’m off work though, I may do more walking (when it’s not a hurricane outside or -30 C).

          11. Bruce Trail, Grand Valley Trail, Oak Ridges Trail…We do them all year, snowshoes when necessary. Did our first of the season last week with cleats on in about 2″ snow. Last year was a pain after the ice storm, though…If this California girl can handle the cold, you dyed-in-the-wool Canuck certainly can;-)

          12. I have a lot of body pain with lots of migraines so I’m often loathe to walk outside though I find the cooler temperatures – Fall & Spring the best times. Otherwise, the bugs love me in the summer (I think it’s because I sweat more than most when I exercise) & winter is cold then you bundle up & get too hot, though I have to say, winter is better than summer when you’re in the woods because there are no bugs and you can often spot wildlife more easily. It’s been a while since I’ve gone for a walk. I’ll have to start again in the new year if I’m able.

          13. My bum sympathises after the squats we did at the gym yesterday. Squash is a great game for bums, but also hard on the knees. Don’t play any more.

          14. I know a guy who messed up his feet playing squash. Hurt his toes with all the running & sudden stopping.

          15. 485 with hips below knees, even just for one repetition, is a damn-sight more than decent.

            We are talking regular old free-weight squats in the squat rack?

        2. But see my last response above. While you’re right about height and weight scaling differently, its also true that weight differences in dimorphic animals is huge compared to the weight difference humans.

          Let’s reverse the question: can you name an animal species that biologists consider to be significantly dimorphic, where the male/female difference is 8% in body length and 18% in weight?

        3. On major lifts, lifts which engage primary muscle groups, such as squats, dead lift, bench press, military press, I was capable of lifting between 2 and 3.5 times more than she was.

          How much of that is technique, I wonder? Not that I’ve ever spent more than 30 seconds in a gym without feeling physically revolted, but there does seem to be a real difference in the effort and technique the the wife puts into physical things compared to me. She severely struggles to get a 20kilo bike onto or off the bike rack on the car which I practically throw on. I don’t need to put it into practice very often these days, but when the need calls for it, I can still lift and carry a 90kilo log or a 120kilo gas bottle. Not as fast as I could when I was 14, but I can still do it. It really does seem to be a lack of application, or skill, rather than strength.

          1. Height makes a difference. I pour water in my fish tank by carrying it in 5 gallon containers from my water barrels either outside or down a flight of stairs, then lifting those & pouring the water in the tank. Water is 10 pounds/gallon. If I carry those, it is easier if I lift them up to chest level. In contrast, a tall person can just pick them up & walk without a struggle.

            Gravity is a cruel mistress. I think if you’re short, you need to none much stronger to get things done.

          2. Technique in lifting, whether technical weight lifting like squats or clean & jerk, or real world situations like lifting a 90 kilo log, is a very large factor. Both in how much you can lift and in probability of injury. My wife has very good technical form.

      4. 8% is not small. If I were 8% faster at swimming I would have had the world record in every event. Likewise woman’s records would approach men’s. If athleticism were selected for in woman they would probably become taller and stronger to the point where that difference vanished.

      5. The disparity in average weight between human males and females is around 20% as compared to a roughly 26% difference for chimpanzees.

    2. And why do you consider “sperm” the primary object of selection and body size the spandrel, rather than the other way around? How does your hypothesis explain the correlation among species between polygyny and variance in offspring number? And, most important, how does it explain the correlation between body size and mate attraction–the palpable fact that bigger males ATTRACT AND KEEP MORE FEMALES? Finally, it doesn’t explain differences in color and behavior in other species that aren’t due to testosterone but still attract females.

      The male-male competition hypothesis is far more parsimonious, while your hypothesis doesn’t explain the observations.

      1. Is there any reason to think there is a pheromonal effect of the higher levels of testosterone in males? Just wondering if there is more to mate selection than visual display. Females are supposedly more sensitive to odors and also supposedly less aroused by erotic imagery (see sales figures, pornography; advertisements, beer). It’s hard as an uninformed layman to tell where culture and conditioning end and biology begins, but surely the cultural cues are informed by evolved animal instinct?

        1. There are, I think, studies that show that our rudimentary sense of smell does influence our behavior toward the opposite sex. Nevertheless, I am sure we can get very clear and predictable responses between men and women by having them look at pictures of the opposite sex, and judging them for being attractive. I think we are mostly visual now.

          1. I’d second that.

            I faintly remember a crude blind study done with women smelling some clothes from different men and rating it.

            After that they were shown pictures of the men and those deemed attractive didn’t smell better.

            But I guess we’d have to find some good-looking men and women who smell awful and see how they fare mating-wise.

            Is the eye really bigger than the nose?

          2. Some people do better in warm, humid, low-light conditions, some when it’s bright but cool and breezy. The human niche is broad.

      2. And why do you consider “sperm” the primary object of selection and body size the spandrel, rather than the other way around?

        Because in animals where we think the latter is the primary object of selection, we see much bigger size differences.

        How does your hypothesis explain the correlation among species between polygyny and variance in offspring number? And, most important, how does it explain the correlation between body size and mate attraction–the palpable fact that bigger males ATTRACT AND KEEP MORE FEMALES?

        Do they in humans? Does the correlation see in other animals hold for us? I’m not aware that bigger men attract and keep more women on average. AFAIK, we are a serially monogamous species for the most part. As I said in my first post, I’m happy to accept the selection advantage of dimorphism for a lot of animals. I’m also happy to accept your other examples, such as sexual selection of coloring and so on in many many animals. What I’m saying is that no such hypothesis is needed to explain human sex differences.

        The null hypothesis explains it adequately. Give women the same anabolic steroids that are present in men during their development, and they’ll be just as big. No other genetic difference is needed to explain what we see. And while I don’t know this for sure, I would bet that the developmental differences in truly dimorphic animals (such as deer and sea lions) depends on a lot more than that; that there are a lot more genetic differences triggered.

        Lastly, if you think dimorphism is the result of selection, why do men live 10 years less? What adaptive advantage does that confer?

        1. Several things here:

          (1) Monogamy in humans is not relevant here: the relationship between polygyny and variance in offspring number BETWEEN species is a totally different thing than the relationship between polygyny and variance in offspring WITHIN one particular species. You can’t use one of these ideas to inform the other; they are different things.

          (2) You asked, “Does the correlation in other animals hold for us?” But this is a form of the Fallacy of One. The correlation Jerry is refers to is one BETWEEN different species. You can’t expect a single species to “conform to a correlation”; indeed, I don’t even know what that phrase would really mean. You can observe the correlation Jerry cited between species, but that does not by any means imply that one particular species (here, humans) should be expected to fall nicely along the line neatly defined by such a correlation. Finding one example that doesn’t fit the line well does not nullify the fact that the correlation still exists (and so needs to be explained).

          (3) A null hypothesis explains nothing unless it matches the data. The presence of sperm or high levels of testosterone to explain size differences in the sexes does not comport with sexual dimorphism in many species (see my phalarope example below, or the one below that about seahorses). Further, Frank’s post below is a good one because it points to the fact that we are talking about a continuous scale; i.e. there are degrees of sexual dimorphism that need to be accounted for. You seem to be arguing for a binary response though: provide the anabolic steroids and females will become as big as males.

      3. And, most important, how does it explain the correlation between body size and mate attraction–the palpable fact that bigger males ATTRACT AND KEEP MORE FEMALES?

        Size of harem isn’t simply related to reproductive success. There is a significant amount of “infidelity” around the margins of any harem. A couple of months ago we were out hill walking and encountered (by binoculars) a (red deer) stag and harem ; while the stag was facing off with a competitor, at least one of the hinds was getting a load from a third party stag who had been hanging around.
        I’m pretty sure there’s an ecological term for this “hanging around looking for a quickie behind the bike sheds” strategy, though I can’t recall it.
        what are the stats for “infidelity” in hoomins? I see claims up to 30%, which may be a bit high. But 10% may be a bit low. It probably varies across societies.
        That doesn’t invalidate the effect of body size in competition, but it will erode the degree of the effect.

          1. That is exactly the term I was thinking of, but my mind tells me there’s a $20 (CAD, in fine silver) phrase in Latin that amounts to the same.
            For phrases like this, Google isn’t much of a friend.

          2. Kleptogamy (from the Greek) was coined afterwards, to placate journal editors uncomfortable with Anglo-Saxon.

          3. There’s a funny bit in a Robert Sapolsky book. One of the baboons he is studying has a slight stature and timid nature so spends a lot of time grooming females but can’t be (seen to be) doing more with them since the big guy gets dibs on that. Sapolsky feigns surprise that so many of the babies born look like him.
            The baboon, not Sapolsky.

          4. Kleptogamy … that would work, but my first impression is of an organism where the male fishes out the previously-implanted solidified semen plug from the female (a common anti-cuckoldry strategy) and noms down on it (“Yummy! Dried cum – someone else’s effort goes to my digestion!”) while getting his leg/ tentacle/ pseudopod/ appendage over.
            But kleptogamy sounds good enough for these purposes.

    3. Your post fails to account for the fact that the DEGREE of sexual size dimorphism (as well as the direction) is well explained by observed variation in the intensity of male-male competition and degree of polygyny. Thus, males are nearly twice as big as females in gorillas, which are highly polygnous, whereas the difference is 8-10% in humans and chimps (all of which produce sperm!). Another example: there is a well-established positive correlation between degree of SSD in pinnipeds (sea lions, otters, seals, etc.) and male “harem” size (I don’t like these anthropomorphic terms, either), and, again, all pinniped males need testosterone to produce sperm. So your alternative hypothesis is easily rejected as unable to explain interspecific variation.

    4. Not to pile on here, but another thing to consider is that if sperm or the presence of high testosterone levels was the primary object of selection, then species where these traditional sex roles are reversed make no sense. Take the phalaropes, for example. Females compete for males, are more aggressive, brightly coloured, and bigger than males. Attributing these sex differences to female-female competition is pretty natural, and totally analogous to what we typically see in species where males compete for females. If sperm or testosterone level was the main causal agent, then we would have to generate a totally disparate hypothesis to explain sexual dimorphism is species like the red phalarope. That destroys all parsimony.

      1. I’m now wondering about seahorses (which I keep incorrectly calling “horse fish” lately) where the male must carry the young fish.

          1. The males have the larger parental investment because they end up carrying the fertilized gametes. So female competition over males should follow and no additional theory is needed to explain this behavior in seahorses.

          2. I recollect reading because female marine animals disperse their eggs in the ocean or river beds they have the first dibs at high tailing it. Leaving the male with two options, release sperm and leave or hang around and take care of the young. Those that do hang around must be able to identify their young that would be a major factor in choosing this as a mating and propagating system. So a courtship ritual, nesting, possibly protection leading up to egg dispersal would cover that aspect for the male.

          3. I always wished I could lay a bunch of eggs and forget about it! Proabbwly there’d be some egg laying version of The Fall & women would have really bad ovulation pain! 🙂

      2. In spotted hyenas the females are larger and more aggressive than males. They also have high levels of testosterone, which is because they need it to produce sperm, I suppose.

    5. Just because we , as humans , can determine some of the mechanics that produce the dimorphism doesn’t affect the reality of it.

      And, I’m not sure simply adding testosterone to a girls development may not have some unintended consequences as the female hormone balance is also a factor.

    6. The problem with the “secondary effect of steroids” hypothesis is that it just assumes larger and more muscular are inevitable side effects. It is at least equally likely that the response is the evolved mechanism by which larger size, favored for the reasons discussed in the piece, is achieved (i.e., “I’m in a body producing testosterone so I should grow more”).

      1. yes. Secondary effects of sex hormones are not ineluctable. They can be added or removed fairly easily through changes in the expression of receptor/signal-transduction systems in different tissues. For example, experiments have shown that testosterone supplementation increases growth rate in some species of lizards and decreases it in other closely related species. And it follows exactly the pattern predicted from their different patterns of sexual dimorphism.

    7. eric,

      The idea of substantial size difference being a “spandrel” is completely implausible. By definition, spandrels are traits on which there is no selection pressure. But things like size and muscle mass directly and hugely impact metabolic costs. Extra mass needs more calories and oxygen and can cause more problems (like cancer). Tissue is costly. These are never, ever traits that selection will be mute on the way it might be re: blood color.

      1. Not to mention that another cost is reduced immune response sytem, something that’s highly costly. The only reason for the denial of this obvious fact is ideological wishful thinking. Sadly it’s pretty common

    8. I don’t want to be rude, but that’s a ridiculously simple view of the role of testosterone, and not even close to correct.

      Gibbons aren’t dimorphic with respect to size, despite males having a lot more testosterone in their systems than females. That fact alone should have given you pause.

      Quite apart from that, building bodies takes time and energy, both of which could otherwise be devoted to reproductive activities. In evolution, you just don’t build bigger than you have to, and no simple metric such as hormone level is going to prevent selection from clamping that size.

      On average, women are about 1/2 as strong as men in upper body strength, and 2/3 as strong in lower body strength. Men aren’t all that much taller than women, but they do have considerably more muscle mass.

      That’s a fact that requires explanation, and that explanation is not going to be any kind of socialization, or some random side-effect.

  2. Sperm is cheap? Seems to me that a lot of effort/investment is put into building up and maintaining a territory or harem!

    1. Shouldn’t terms like “cheap” and “scarce” be considered relative to the alternative? In the case of humans, it should be obvious that female gametes are much more scarce than male gametes.

  3. Yes, this, this this. I’m also a leftist biology major, and this is an endless source of grief with me. It seems to be a stumbling block that many leftists, especially feminists, aren’t able to address or get past. And they way that feminists basically endorse the naturalistic fallacy is quite disheartening.

    I wrote a post on this topic on my blog as well: Yes, There is a Gene for That: http://www.rationalrevolution.net/blog/index.blog?entry_id=2328845

  4. My personal view is that it should be widely rejected because of the second word, “psychology,” which you spend very little time talking about. Whatever we make of psychology, there is certainly a relationship between behavior and brain/mind and evolutionary processes. The problem for much of evolutionary psychology has to do with the ensconcing of human psychology and human social behaviors. Evolutionary psychology runs into ubiquitous problems as it begins talking about what exactly is genetically being structured for (or against) in human social affairs.

    The main crux is the range between what genes (and hence evolution) are structuring and the psychological traits of humans. For the most part, evolutionary psychology relies on the idea that our folk psychology is representing our psychological life in some useful way. And from such, begins talking about evolutionary structures for those traits.

    Most sexual dimorphism claims are surely a fact. I would argue that is not the stream of evo-psych that is being rejected by most people who reject it. The idea that body and brain mechanisms is significantly different in males and females across the animal kingdom is undeniable, and that often has to do with differing behaviors and different social roles. As we use similar explanations to describe human behaviors, especially psychological traits and institutional structures, as evo-psych often does, the ground becomes much more shaky.

    1. I honestly did not understand what your grief is, sorry.
      Is it just me? Or what is the issue according to Lyndon?

    2. “the problem for much of evolutionary psychology has to do with the ensconcing of human psychology and human social behaviors. Evolutionary psychology runs into ubiquitous problems as it begins talking about what exactly is genetically being structured for (or against) in human social affairs.”

      I’m not sure what is meant by the ensconcing of human psychology” or “genetically being structured”, but virtually any human behavior that can be quantified in a reliable way shows a non-zero heritability, i.e., some portion of the phenotypic (observed) variation in the behavior is due to underlying genetic variation. How could it be otherwise, since there is often allelic variation at the many genes that influence how the brain is formed, and how it operates? It is true that parsing out genetic variance for human behavioral variation is difficult (in the absence of controlled experiments!), but it is too easy to say that there are “ubiquitous problems”.

      1. “some portion of the phenotypic (observed) variation in the behavior is due to underlying genetic variation.”

        The problem with that claim is this:

        Slave behavior (“observed variation in behavior”) in 1800 US was “due to underlying genetic variation.”

        Is very much a true statement. It is just questionable what it tells us about genes structuring for behavior. “Due to” becomes confusing, and that is going to extend beyond when we have absurd social conventions to all sorts of different social contexts and the behavior in question.

        1. My “claim” has been empirically demonstrated many times, whether or not you perceive a problem with it. “Slave behavior” is a complex outcome of many individual behavioral tendencies (as well as strong societal/environmental influences), and it is a bit of red herring to use it to doubt the heritabilities of underlying component behavioral traits. It is of course true that all human societies form dominance hierarchies (as do all social primates), and culturally universal traits often reflect an evolutionary basis (e.g., the incest taboo). Ditto for the ubiquitous xenophobia noted by Professor Coyne.

          I still don’t know what you mean by genes “structuring for behavior”. Technically, speaking, there is no such thing as a gene “for” a behavior, but we use it as shorthand to note that the actual gene products (proteins) certainly do affect brain functioning, personality (“shyness” runs in families, for example, as does schizophrenia), etc., and their is often abundant variation in these proteins that affect neurotransmitters, hormones, and the like, that affect any number of quantifiable behavioral spectra (shyness vs. aggression, curiosity vs. dull-mindedness, neatness vs. sloppiness, etc.)

          1. Hi Frank, last post for me,

            I agree with your later description, which is all I mean by “genes structuring for behavior.” When you say that we have measured “underlying genetic variance” I assume you are making a statement that such genetic structures have salience in the behavior in some way. The question here is in what way? What does this tell us about human behavior?

            My difference is with your claim about “component behavioral traits.” I do not believe you can ever define them in a way better than the problem of the slave example. Perhaps better than that, but it bottoms out in the same problem. What you think you are describing as a “behavioral trait” will always be an empty categorization. That is, unless you go real small, but then your trait will not look like a trait, in most people’s parlance. It may be that such small effects map onto broader social and psychological structures, but the way that those small effects blossom into larger behavioral phenomena would be highly contingent. This would require large scale institutional and environmental explanations.

            It is such a problem that you could not explicate and defend any kind of behavioral or mental trait as a useful, steady account of the world. And that is psychology’s problem in general, let alone EP’s. It also does not help that with a slight social twist (with the same genetic variance) we could obliterate your “trait”, and still have robust, viable individuals.

        2. In your comments here you seem to be saying that because EPs practitioners have done a fair amount of bad science in its brief history that it isn’t worth pursuing. You also seem to pretty clearly be saying that because we can not, right now, figure out the details and accurately model it that it isn’t worth pursuing. Neither of those seem relevant. All investigations start out that way. You make progress.

          Slave behavior (“observed variation in behavior”) in 1800 US was “due to underlying genetic variation.”

          I understand that is just a simple example to illustrate a point, but I just don’t get it. That statement is as bad or worse as any made by crank EP scientists. No one with a clue thinks underlying genetic variation is the only, or even the only significant, factor contributing to behavior.

        3. Oh I see now what you mean. You are fed up with the shallow “due to genes” pseudo explanation, which echoes the “because culture” way of saying stuff happens.
          But EvoPsych has actual hypotheses, like how parental investment works, why it works the way it works, how moral instincts work (kin selection and reciprocal altruism and many interesting wrinkles into that on how to spot and deal with cheaters, how to signal, honestly or dishonestly, your good characteristics etc), so EvoPsych isn’t just “because genes”, it is a direct continuation from the kind of biology you might read in biology in general, just applied to humans.

    1. I’m not sure that that question needs to be answered anywhere outside a philosophy or language theory department, if it needs to be answered at all, given that it is the sort of question that has dug the ground out from under its own feet.

      1. I came of age during the rise of postmodernism and I could not quite reconcile how embracing relativism (in gender, cultures, what have you) meant rejecting differences, as if doing so automatically implies a value judgment. Different is not necessarily a value judgment, and I would expect that is the foundation of what I would call relativism.

        Ironically, there was a propensity among postmodernists to assert that the attributes of traditionally oppressed or undervalued classes were intrinsically better than Western norms, as if that superiority were the reason for the oppression. I’m sympathetic with “power” movements, but only so far as they are about asserting equality.

        Having said that, I can’t help but feel like the women in my life are “better” than I am, but that’s a personal value judgment: they are better multi-taskers, more socially aware, more hygienic, and better planners. It feels like it’s a biological difference, but “better” is a value judgment I apply (and I suspect they apply!) that is independent of the larger judgment of balancing traits and equal value as human beings.

      1. There is the post modernism essay generator.

        You generate a new essay by clicking on a link. At the end of the essay, you will see this message:

        The essay you have just seen is completely meaningless and was randomly generated by the Postmodernism Generator. To generate another essay, follow this link. If you liked this particular essay and would like to return to it, follow this link for a bookmarkable page.

  5. A slightly mischievous thought has just occurred to me on the subject of evolutionary psychology. I haven’t had time to research it but I’ll just put it out there.

    Evolutionary explanation for wife swapping.

    Suppose a couple wanted to make sure that their marriage didn’t fail due to one or both parties getting bored and so they decide to try out wife swapping. The husband risks loss of the certainty that some children may not be his own for the possibility that some children that he sires by another wife could be. One result will be that he will be very enthusiastic in his love making of his own wife to ensure that he has the greatest chance of being father to his wife’s children. This activity could help their relationship in that it both spices up their love life and satisfies both partner’s urge for experimentation and wandering.

    For the wife’s part, she gets the greatest chance that at least one or more of her children would great genes (if her husband’s are in any way wanting) without the associated risk of abandonment by her husband due to her cheating.

    1. In humans this behavior is not aimed at reproduction, so the issue about relationships to children is likely off the table. I think the behavior is a kind of spandrel, that is it came about by natural selection but it is in this circumstance not an adaptive behavior.
      Of course plenty of animals perform this practice even among seemingly monogamous species. They hedge their bets in the traits of their offspring this way.

      1. I don’t see any reason to assume that the causes of the ‘same’ behaviour in fairy-wrens don’t operate in humans: do you have evidence to reject the null hypothesis? It may be that swingers use contraception more than the average person, but it’s always been a wise child that knew his own father.

  6. Fascinating. Reading your posts is an ongoing liberal (and scientific) education. Thanks for this one and thanks very much for all of them.

  7. Whenever the discussion includes the personal view does that mean forget the science.

    I would guess this discussion would also include the violence difference between the sexes as well. It is a fairly one-sided affair so the statistics say and not the personal.

  8. Excellent post and certainly nothing to argue against in it. The point that some assertions made from Evolutionary Psychology premises are very dubious of course is also true. I remember attending a conference where Steve Jones made the assertion that there was in essence a “belief in god gene”. But what validates that thesis vs. an equally valid “believe what your parents told you” gene. When there are multiple equally plausible explanations and no way to falsify any one of them Evolutionary Psychology reaches its limits. But as for sexual dimorphism the evidence is compelling.

  9. Superb. Thanks. Can’t speak for others, have difficulty saying my own thinking, but believe the concept of evolutionary psychology is sound and as happens in so many emerging scientific disciplines subject to criticism, which every scientist on a quest for proofs dismisses unless based on evidence.

  10. Wow. I never knew about the “left-wing opposition to evolutionary psychology”. I really must start reading more.

    I have watched a video several times of a conversation between Richard Dawkins and Steven Pinker in which one of them mentioned something about the tendency of human males to seek younger females as mates possibly being the result of the evolutionary pressure to find mates who are clearly healthy enough to bear children. I started thinking that maybe the tendency of some males to seek out female children as sex partners might be some overlap with this same gene or genes. It seems to me that this area might really be worth researching – maybe it could even lead to a cure for pedophilia.

    Sorry for expressing this so awkwardly – I am no scientist. However, I hope that more brains and money will go into this field, because it seems to me that this could result in better lives for all of us.

    1. A few years ago, I heard about a study that showed that younger females are more likely to care for their mate while younger males were less likely to do so. This was used to explain why selecting a younger man would be a bad idea for an older woman.

      For my own morbidly curious pleasure, I have read forums where women would complain that they had joined dating sites where the men who were older or their age, were only interested in younger women so they were having no luck in finding mates.

      I also recall, in my vastly younger days, tall girls yelling at short girls to “stay away from our men” if the short girls were dating tall men as the tall girls felt they could only date tall men seeing as they were “too tall” for the regular sized men.

      It’s all interesting to me.

      1. We used to have a professor here that taught a senior capstone class where they did a research project that was parallel to some of this. They would compare the Men Seeking Women ads to the Women Seeking Men ads, and ask what each was seeking from the other. the results were always very strongly that the men were generally looking for younger, attractive women. The women were generally looking for gainfully employed men without bad habits.
        I know this is essentially anecdotal, but it really got the students talking and thinking about the social order.

        1. We used to do a similar exercise in our Evolution class, using dating sites and personal ads. The results were the same, and, as we expected, the older the male, the greater the age disparity between him and the woman he was seeking. It was an interesting exercise, and of course the students loved it.

          1. I think the older man/younger woman is more common than the reverse, but I had two long-term relationships (7+ years) in my 40s and 50s with men close to 8 years younger than me. It just happened that way, and there were no issues about it. (I’ve always looked younger, which was a pain back in the day, but kind of nice now.)

          2. A few months ago I read about an analysis of people’s preferences on one of the more popular dating websites (I’m afraid I can’t find the link to the article). The obvious advantage of this sort of study is that it has access to data from hundreds of thousands of users.

            From what I recall, the study suggested, predictably, that women on average preferred taller men, and that men on average preferred women younger women.

          3. It was an interesting exercise, and of course the students loved it.

            Did you have any 50-something male mature students looking very uncomfortable while doing the exercise?

    2. Mary, if you are interested in reading more, you might like E.O. Wilson’s preface to his 2004 reprint of “On Human Nature”. He describes some of the hostile opposition that he experienced when he developed his ideas about sociobiology (the forerunner to evolutionary psychology). As well, Steven Pinker’s chapter “Family Values”, subsection “Men and Women”, in “How the Mind Works” has some interesting explanations of evolutionary psychology, sexual selection, size differences, and mating strategies. They are similar to the ideas in Coyne’s post.

  11. I suppose it is driven by sexual selection in that females select for males that are likely to improve their and their offsprings survival in a predator rich environment. On the flip side, the increased testosterone required for increased size may make the male more likely to die once the children have reached maturity and thus ease population pressure for her offspring. It’s a win/win for the offspring.

    1. Also the degree of dimorphism may have to do with the degree of paternal investment in child rearing. If there is little or none the females will select for traits in the male that will benefit their offspring during the vulnerable premature period, like strong fast muscles for escaping predation. If their is substantial paternal investment then the female doesn’t select for dangerous aggressive traits that are likely to result in an early death when compared to the female lifespan. She will select for traits that are similar to her own that don’t result in the early demise of the co-caregiver.

  12. I would say certainly that the explanation of rape as a phenomenon (Thornhill and Palmer et al) as an Evolutionary Psychology explainable phenomenon is so much more controversial a topic that sexual dimorphism. Here we have both scant evidence and a feeling that an explanation is the equivalent of a justification. Is there any scientific explanation that should be classified as taboo? I don’t think so, but obviously some do.

    1. I wrote two negative reviews of Thornhill and Palmer’s book excoriating them for that hypothesis, and saying that they finagled their data to support it. One review (with Andrew Berry) was in Nature, the other (by me alone) was in The New Republic.

      1. In a letter responding to your review, “Of Mice and Men”, Leda Cosmides and John Tooby excoriate you right back very badly indeed. It seemed very unfair to me.

        1. I think the rebuttal of Tooby and Cosmides is weak, to put it mildly. They do not address any of the specific points raised by Jerry, more a kind of general criticism. That is a serious flaw, not really cutting wood.
          That being said, I still suspect Thornhill and Palmer are basically right (no, not in their recipes for improvement, but in basic causes), but their homework is (as so clearly pointed out by Jerry), how shall I put it nicely, open to improvement?

    2. Explainable or not, rape seems like a maladaptation and/or cheating, and cheating comes at a high reproductive cost – primates have differing levels of male parental investment, but I don’t think zero investment is a stable strategy for any of us. Other pathologies might have evopsych “explanations” (incest, necrophilia) but researchers better have watertight science and be highly sensitive to social realities lest they face intense, well-deserved upbraiding!

      1. and cheating comes at a high reproductive cost

        Cheating has a high reproductive benefit for most primate males. One (or more) extra offspring for the cost of two minutes of squelching and the threat of a battering if caught. If you get away with it … investment and risk over, so move onto the next cheating possibility.
        Corollary prediction : once you’ve shagged her behind her apparent mate’s back and got her up the duff, drop her like a soiled condom and move onto getting the next partner.
        No, it’s not nice. But I can certainly remember males who followed that strategy (Runtissimo, Detective Inspector Wossname, Callum (who never did know that his son’s father is probably Runtissimo) with a better than zero success rate.

    3. I think the whole question of ‘why males rape’ is asked the wrong way round.
      Simplistically put: in (particularly placental) mammals females have greater investment in offspring before they are even born, reason so many male mammals can afford not to invest (or invest little) in their offspring, they can safely desert the female and look for other females to impregnate. Whether a female is consenting or not is not really all that relevant from a ‘selfish’ male mammal point of view.

      The question should be: ‘Why do males *not* rape?’

      Possible answers would include eg. aggression by other males, resistance from the female (despite sexual dimorphism) and resistance from other females -and males- within social networks.
      Laura Betzig showed in her “Despotism and Differential Reproduction: A Darwinian View of History” that male despots -men who have power over life and death- use their power to get access to females. Rape is very common in situations where there is no sanction, such as war, slavery and indeed harems.

      1. <in (particularly placental) mammals females have greater investment in offspring […]. Whether a female is consenting or not is not really all that relevant from a ‘selfish’ male mammal point of view

        Sex also feels good. Surely the proximal explanation may also be sufficient. (Or do women never commit rape?)

        Laura Betzig showed in her “Despotism and Differential Reproduction: A Darwinian View of History” that male despots -men who have power over life and death- use their power to get access to females.

        …and fast cars, fancy jets, nice food — in general, things that are enjoyable to them (i.e., highly valued resources). Again, I don’t see why a proximal explanation isn’t sufficient.

        (And this is exactly the kind of facile reasoning that drives some people nuts about evo-psych.)

        1. And, of course, the evo-psych account does not explain why so many rapists kill their victims, or why they often humiliate them, all suggesting that the act has more to do with power than sex.

          1. Certainly, from the victim’s perspective, it is all about power, not sex.

            However, for a completed rape, the rapist must have an erection — sex.

            Power (violence or threat of it) in this case is typically used as a means to an end (sex).

            Bank robbers would not bring guns if tellers would simply hand over the money without such a threat.

          2. But your argument is like claiming that bank robberies are about all about guns, since that what is always used in a bank robbery.

          3. Most* murders are done to cover up other crimes. Effective societal sanctions against rapists unfortunately create the motive to effectively silence witnesses.

          4. That doesn’t explain why many rapists humiliate or commit sadistic acts against their victims. Look at Cosby and Ghomeshi — two famous, powerful men who would have had no difficulty finding willing sex partners, yet both seemed to get off on forcing women into having sex with them. Sure, it was about sex, but it was also about power.

          5. That doesn’t explain why many rapists humiliate or commit sadistic acts against their victims.

            Because misogyny is also adaptive. For an individual in a small band where resources are limited, reproductive success is a zero sum game. Any female who isn’t boffin you is helping some other guy spread his genes. If you are a female, then any other female getting any is taking from your offspring. The best way to help your offspring win the competition is to prevent your competition from having offspring.
            The prediction is that there will by misogyny in both males and females and that that misogyny will be directed especially against females in sexual display hence the passionate hatred of sluts (girls who like sex) but not of nuns.

          6. So misogyny is also a product of adaptation? Really???

            Seriously, these kind of pseudo-scientific Just-So stories are precisely why so many people are put off by evo-psych.

          7. @kevin7alexander

            Actually slut-shaming among men only appear when men are expected to invest and care for the offspring, then it’s necessary that men have paternity certainty which is impossible if the woman has sex with several other men. Slut-shaming is more widespread among women and is a form of intrasexual competition, by labeling some women as sluts they want men to divert their investments from those women since it evolutionary is risky investing in offspring that isn’t certainly yours. Also when women become more promiscuous, men invest less in women and their offspring so slut-shaming is a method women use to make women less promiscuous and thus keep male investment high.

          8. slut-shaming among men only appear when men are expected to invest and care for the offspring


            Slut-shaming is more widespread among women


            and is a form of intrasexual competition


            slut-shaming is a method women use to make women less promiscuous and thus keep male investment high


            (Once again, I cannot stress enough that it is precisely this kind of smug, simplistic, data-free Just-So storytelling that causes people to not take evo-psych seriously.)

  13. We obviously come preprogrammed with a multitude of psychological “routines” like falling in love, bonding with our offspring, and feeling, not just simple emotions like fear, desire, and anger, but social emotions like pride, jealously, guilt, loneliness, and shame. These psychological routines motivate behavior that has fairly obvious benefits for survival and reproductive success. Denying the role of natural selection in producing these psychological aspects of human nature seems no less absurd than denying the role of natural selection in creating our physical nature.

  14. “ecological differences don’t seem to exist in our closest primate relatives” – yet can we really be sure that differences in humans do not stem from, or have contributed to, differences in roles (in the past)?

    Does it depend where one stands on the place of meat in the development of early humans? If we were scavengers, driving predators away from kills, that would favour larger males, as might hunting, but if they were opportunists & just ate meat when they came across it that would favour the idea that larger males were slightly at an advantage.

    If fact the size differences are not so very big, which suggests that multiple mates at any one time are not a human norm, I would say… Besides which the invention of tools changed everything – size would no longer be as useful.

    1. “that would favour the idea that larger males were slightly at an advantage” – in mating with more females rather than it being due to hunting I mean…

    2. “If we were scavengers, driving predators away from kills, that would favour larger males”
      You went wrong on the last word, there. It might favour larger body size in humans, but you didn’t begin to explain sexual dimorphism. Easy trap to fall into.
      The idea that males and females diverged in diet to reduce competition between the sexes has been argued, but it seems to rely on a group-selectionist idea (treating the sexes as competing groups) and is therefore almost certainly bunk.
      Another possibility is that females with infants are less mobile and hence more dependent on plants and small animals, while males are free to go on longer and more energetic hunts; this may have something going for it, as an alternative or supplemental explanation for dimorphism in humans.

  15. One of the objections to evo-psych is that it’s impossible to filter out the social or cultural effects on behaviour – which is true – but only to the extent it’s also impossible to filter out biological factors when assessing cultural effects.

    My objection to the blank slate model is that I wasn’t a blank slate. I have Aspergers and that is a development disorder and so rooted in biology.

    The blank slate argument that psychology is cultural is actually a belief that neurotypical minds are culturally determined; autistics, schizophrenics, people with bipolar disorder, etc. are shuffled off to one side as exceptions: Neurotypical minds are ‘cultural’; neurological disorders are ‘biological’.

    But if our minds are profoundly influenced by biology why not everybody else? Why the shame in admitting it?

    It’s just that, being in a majority, neurotypicals assume that their brains are entirely free of biology – which makes them unique in the animal kingdom.

          1. +4

            My explanation is, a persistant desire for, and belief in, human exceptionalism. It is common even for atheists and cultural / liberal theists, and deists. Even for many people that claim to have no truck with religious explanations / reasons for human exceptionalism, they just seem to grab on to other means of justifying it, like science. I really don’t get it. What is so lacking about “There is no purpose but what we make?”

    1. One way of looking at this is to consider autistic traits, for example, existing on a spectrum. At one end you have autistics, at the other extreme empaths, but most people are clustered around the middle. It would be absurd to imagine both ends of the spectrum are biologically determined while those in the middle are biology free.

      You could then ask is this distribution of autistic traits adaptive?

      Well, autism itself might not be adaptive but autism might well be a convergence of traits that, in isolation, might be adaptive: a local processing bias, for example, is adaptive for spotting camouflaged food or predators. Likewise those at the other extreme of the spectrum might have highly adaptive social skills.

      So a distribution of traits might have evolutionary advantages; but that means the majority who fall between those poles are as determined be evolution as the outliers.

      1. A final twist on this; Aspergers is four times as prevalent in men than women.

        Since autism is a spectrum disorder this might well be because men already possess more (sub-clinical) autistic traits to begin with.

        Which is evidence of sexual dimorphism in the brain.

          1. If I many freely add to that without any proof or data whatsoever: it has often seemed to me that I have a hard time sorting out what my wife is saying to me when there is also noise like clattering dishes, or a squeak in the floorboards just then. We often laugh about that.

          2. I have trouble, too, when there are all kinds of ambient noises. There was once a play called “I can’t hear you, the water’s running.”😸. My bf is kind of hard of hearing and is always saying stuff to me when I’m near the running water and he doesn’t realize that said water is running…

          3. I have found that I find ambient noise frustrating. I don’t like going to restaurants that play loud music. I attribute it to being middle aged. 🙂

          4. A decade or two ago, I was an NPR junkie and always had the radio on. Then, I took a trip to a family reunion / funeral ceremony in northern Nevada. I discovered that I positively loved the silence. I never did turn the radio back on when I got back from the trip.

            One of my biggest regrets…is that my refrigerator, which I bought based in large part on its Consumer Reports rating, isn’t nearly as silent as I expected it was going to be. It’s not loud as such things go, but it’s far and away the loudest thing in the home.


          5. I’ve always been good with silence. Perhaps it is because I was an only child & tend toward introversion. I also find that if I’m trying to think, I prefer absolute silence, including thinking about things while driving (but usually I’m just rocking out to tunes, hoping no one I know sees me – when I’m in my convertible, I make sure I do that when I’m on the country roads & blaring Falco isn’t heard!) 🙂

          6. I even gave up on the radio in the car at the same time.

            In fact…I have no clue if the radio in my ’68 VW Camper still works or not, and I know the radio in my new-to-me ’64 1/2 Mustang doesn’t work. It’s the original radio, and there’s some funky electrical stuff going on that is almost certainly responsible for the radio, so it should work again when that’s all straightened out, but it’s an AM-only radio.

            And I have no plan to replace it.

            (If I did feel inclined to do so, I’d probably just go with something that could wirelessly stream from an iPhone and hide all the non-original equipment.)


          7. I usually play some sort of iPod in my cars either listening to Audible books, Podcasts or rocking out. Otherwise, I just listen to CBC. My news is mostly listened to so I often don’t know what politicians look like until I go google them later. 🙂

      2. Since autistic people lack theory of mind but not empathy, perhaps they spectrum is more like a matrix. Sociopaths and narcissists could fall in a “lacking or diminished empathy quadrant, typically empathic somewhere else and extremely empathic (where I see myself – and believe me, empathy doesn’t make you nice, it just makes you feel bad when you aren’t & it makes you pissed off when someone else is pissed off — I have to remove myself from those situations) would be in another quadrant.

        Then you’d have those with & without degrees of theory of mind (or maybe it’s a binary thing).

        That was my tangent as I’ve been thinking about/reading about both empathy and theory of mind a lot lately.

    2. + a lot. I hate this dualistic notion. I consider it a horrible evil because it stigmatizes people as choosing to be however they are.

    3. It’s just that, being in a majority, neurotypicals assume that their brains are entirely free of biology

      I’ve never talked deeply on psychology with another “neurotypical” who has thought that their lives and minds were devoid of biology.
      Then again, I’m often accused of being well off down the Aspergers spectrum myself, so that may be an irrelevant observation. (My answer to the accusation is, of course, “So?”)

  16. I wish I’d read this a few days ago. I got into an argument about whether it was valid to view sex as biological, but gender as an entirely social construct. My argument was that while gender norms may be a sociological construct, I felt that the person I was arguing with was being too ambivalent about the degree to which hose societal norms are informed by biological dimorphism.

  17. There are essentially two problems in studying something like evolutionary psychology:

    1) Attempting to avoid circular arguments i.e x has y because x evolved z, but x evolved z because x has y.

    2) Confounding the variables of the biological factor with the social factor. Since no one is raised in a social vacuum, we cannot definitively say if any difference as due to the biological factor or the social factor (or both).

    That’s why cross-cultural studies are quite useful as they give hints on what may be a social effect. Not that it’s impossible to study the field, but the problems are there.

    1. I think cross-cultural studies are useful since they demonstrate that evolutionary psychology is about what human beings have. in common.

      The cultural determinists seem to be the ones obsessed with making out human beings are more different than they actually are.

      1. I think cross-cultural studies are useful since they demonstrate that evolutionary psychology is about what human beings have. in common.

        Or they could demonstrate what the people doing the cross-cultural studies have in common.
        Send two linguistic students to record thirty Papua New Guinea languages (advert : two books by a friend with PNG history). One student speaks French only ; one speaks Spanish only. How many languages that they study will have elements reminiscent of Latin?

  18. Isn’t the fact that females tend to prefer males as sexual partners and vise versa a good example of the fact that male and female psychology is different?

    1. Arguably, that’s a way in which male and female psychology is the same, not different. Since it can be stated either way, there’s probably no right answer.

    1. I think I read that polygyny is the dominant mode among mammals, but very rare among other vertebrates (or at least among bird species). So I wonder if the question isn’t why monogamy evolved? There’s an obvious correlation between male-female ratio; humans are basically 50:50 with slight female advantage; a large female preponderance would necessitate polygyny; and extreme female preponderance would require polyandry to survive. So is there a chicken-and -egg situation there?

      Fun fact: in addition to minimized dimorphism, monogamous males have relatively smaller testicles than do males of promiscuous species. It’s a supply and demand type deal.

      1. I think you’re probably right that the right question is why monogamy evolved. I wonder, though, about the correlation between polygyny and sex ratios.

        Brian Skyrms (http://www.jstor.org/discover/10.2307/2940983?uid=2&uid=4&sid=21104666982041) created a model that shows how evolution might put pressure on a species to produce a 50/50 sex ratio (basically, if you define ‘fitness’ as the number of grandchildren one has rather than the number of children, then the species should be 50/50 at birth). I couldn’t find anything immediately about whether Skyrms’ model holds in the real world, i.e. whether sex ratios for mammals really are 50/50.

        Also, what would a correlation between polygyny and sex ratios predict if females were scarce?

      2. Oh, on the point of testicle size; I show a picture in one of my classes of a human hand holding what looks like a pink and shiny grapefruit. I ask them what it is (they do not know). Then I tell them it is the testicle of an adult male chimpanzee. Always gets a gasp.

  19. Personally I’m really psyched (pun intended) to hear our host both endorsing evopsych as a valid field and reporting that there is good science going on in the field. If the research is hindered by skepticism that you can do science because we can’t inspect brain functions the way we might physiology from fossils and genomes, or because there is cultural resistance to the concept of brain evolution, that would be a real shame.

    The little I’ve come to learn about evolution, admittedly almost entirely from Coyne and Dawkins, makes me think the conventional deception from biology we make for the mind – and by extension social constructs – is limited by adherence to dualism. There is every reason to think those genes of our are blindly, silently running the show and all our notions of self and relations among selves is an artifact our brains generate. Which means they are potentially understandable in evolutionary terms.

    I very much look forward to future advances in understanding. The implications for developing truly effective mental health treatments is just one of the benefits I imagine will be a by-product of the work.

        1. I’m now trying to work out a “slit” to work into “Freudian autocorrect”. Thank you. Not. Have a cat. 😽

  20. Interesting post! I’m often puzzled by resistance to evolutionary psychology. Your comment “that our brains and behaviors, like our bodies, show features reflecting evolution in our ancestors” seems so obviously true. Yet, it has to be stated because too many people really resist that idea by either denying it or downplaying its significance. Sometimes, I find that people think that evolutionary psychology is too reductive. For example, parental investment gets translated into justifications for adulterous men and nesting women. That would be reductive. But evolutionary theory explains evolved mental mechanisms that are the basis of behaviour and that characterize it. Obviously, that behaviour can still be pretty wide-ranging and open to change. Your concluding comments on learning effectively account for differences and changes.

  21. In 7th grade in gym class, I remember a girl I had a crush on comment excitedly to one of her friends about liking boys with hairy legs. I was a late bloomer, and was suddenly self-conscious and embarrassed of my naked legs. Since then, I’ve never met a female that was attracted to “hairy men”. I’ve always wondered if being hirsute is sexually advantageous for men attracting a mate like height is. And if being hairy is advantageous, why? More testosterone = more virility? Perhaps it is just something young girls like because they know the male has reached puberty.

    Anyway, thanks for the interesting post.

  22. You’re basically on the money re: size dimorphism. And it isn’t even just about raw size difference. The male body is weaponized. We have disproportionately-concentrated upper-body strength and twice as much muscle as a proportion of body weight. Men might be more given to strokes because our blood clots more readily; useful if you get injured more often.

    I would add:

    Evolved physical features in any organism (that are adaptations) are useless without simultaneous behavior-control adaptations to use those forms properly. The bird’s wings are useless to it, unless it has a brain that can learn how to fly. Even a bacterium’s flagellum is a waste of proteins, unless it has the means to connect sensation of the environment to flagellar activation (behavior). Behavior is inseparable from adaptations of form.

    The gross parameters of our bodies can evolve relatively quickly. Arctic peoples are short and stocky, arid grassland peoples are tall and thin. Evolution would quickly weed out a do-nothing excess of energetically-costly muscle tissue, but the dimorphism has been maintained.

    Sex differences increase with measures of gender equality and egalitarianism, including personality (http://emilkirkegaard.dk/en/wp-content/uploads/Gender-Differences-in-Personality-Traits-Across-Cultures-Robust-and-Surprising-Findings.pdf ) and professional gender segregation (google Gender segregation in the labour market Root causes, implications and policy responses in the EU). These are exactly opposite to expectations based on a no-differences point of view.

    Developmental psychologists have found robust sex differences in infant cognition at all ages studied, some even including newborns.

    1. And it isn’t even just about raw size difference. The male body is weaponized.

      Wasn’t there a claim recently that the human face (male version) is optimised to take a punch in the chops? [Searches …] Yes. Paper and news report.

  23. Late to the party….

    I think objection to the notion of evolutionary and biological components of behavior stems from at least two big sources.

    First, the naturalistic fallacy, of course — that we should actually want what we’ve evolved to be…like arthritis and painful childbirth and propensity to sunburn and skin cancer and…?

    But second is a powerful lingering persistence of dualistic thought. It’s not our messy brains in our dirty bodies doing the thinking, but our pure otherworldly souls, and those souls are free of materialistic taint.

    …and you could very easily insert the entire “free will” (whatever the hell that’s supposed to be) discussion here….

    But, Jerry, as you make so plain, we really are our bodies, like it or not, and it’s up to us to decide if we’re happy with what we are — and, if we’re not, how we want to go about changing ourselves into what we really do want to be.

    Maybe you really do have a strong urge to pick a mate based on biology rather than brains. You might also have a strong urge to eat candy rather than real food and to laze around in front of the TV rather than get out and get some fresh air and exercise. Whether you follow through on those urges and to what extent is up to you…but that doesn’t mean that you get to pick whether or not you have those urges in the first place.



    1. I agree that dualism gets in the way of appreciating the mind as biology; it’s a conventional view which means it it is proportional to conservatism and religiosity. The leftest resistance seems to come more from distrust of science as a (stereotypically) white male and therefore paternalistic enterprise, whatever they might think about souls and whatnot. Of course, the right mistrusts science, too, because it’s science.

      It’s too bad both sides can’t embrace the biology, since either can hijack it: the right can say god made it that way, the left can say we are all equal, everyone’s happy! To the extent a person’s project is advocacy or polemic, there’s just going to be resistance to data that seems to undermine his or her pet theory. That they project their own power trip onto the enterprise of science is regrettable but there it is.

      1. To be fair, humans are exceptional amongst all species when it comes to culture and social organization, the competing approach to accounting for human behaviour. Given that, scepticism about evolutionary accounts is not at all unreasonable.

        1. True. What I had in mind was people acknowledging that evolutionary history / genetic heritage is a significant factor in the behavior of animals in general, but claiming that humans are an exception in that regard.

        2. That seems a bit shallow as the foundation for critique.

          “We’ve evolved beyond ( from our pov ) the competition so comparisons are invalid”….if I catch what you’re saying.

          I think it’s a bit like inserting a miracle into the equation which tries to seperate us from other animals based on the current results of our evolution.

          I don’t think I get it.

          1. “We’ve evolved beyond ( from our pov ) the competition so comparisons are invalid”….if I catch what you’re saying.

            That’s not really what I’m saying. The claim I’m taking issue with is that the notion of “human exceptionalism” is somehow wrong in the narrow context discussed. In the domain of culture and social organization, humans clearly are exceptional — no other organisms have the complexity of social structures, or pass on knowledge to future generations like humans do.

            That’s not to say that evolution may not play a substantial role in human behaviour — I think it clearly does. But I think it is unfair to tar all opponents of evo-psych as some sort of zealots trying to preserve humans atop the Great Chain of Being, because in the case of culture, humans are indeed at the top of that particular heap.

          2. I can dig that although I’d argue that whatever criteria we chose to define our exceptionalism, are very relative terms from individual to individual.

            Evolutionary speaking our social structures and
            passing on of knowledge in its current form is a tiny blip on the radar.

            Regardless, my point was that it doesn’t offer up a critique of evopsych as much as it serves as a rationalization of exceptionalism.

            That culture and other factors adds to the picture doesn’t detract from the foundation of evopsych afaik.

            But of course it’s bad form to dismiss all opponents out of hand and refuse to consider the arguments.

          3. Evolutionary speaking our social structures andpassing on of knowledge in its current form is a tiny blip on the radar.

            Right, and in that tiny blip of time humans have radically altered themselves and the planet, suggesting that cultural forces can be outstandingly powerful and quick. That doesn’t deny that biological forces affect human behaviour, but clearly it is not just biology that took us from hunter-gatherers to Wall Street derivatives traders and astronauts.

            So I don’t see this at all as a “rationalization of exceptionalism”. As I said before, in any reasonable objective sense, humans are radically different than all other species in their ability to shape behaviour by processing and transmitting information. That seems inarguable to me. So I’d say that whenever an adaptive account is offered of behaviour, it is quite reasonable to ask if such cultural forces might not offer an alternative explanation.

          4. “So I’d say that whenever an adaptive account is offered of behaviour, it is quite reasonable to ask if such cultural forces might not offer an alternative explanation.”

            I think that goes without saying that cultural forces contribute to human behavior. What does not go without saying is claiming that genetics does not affect, or is not a significant contributor to, human behavior.

            I don’t think it is accurate to say that cultural forces are a reasonable alternative explanation either. I think it is inarguable and obvious that both genetics and culture are significant factors in human behavior. And that the degree to which each contributes to specific behavioral traits varies.

          5. I don’t think it is accurate to say that cultural forces are a reasonable alternative explanation either. I think it is inarguable and obvious that both genetics and culture are significant factors in human behavior.

            I would completely agree, but such nuance is often missing from such discussions, where instead we read that “X is an evolved behaviour” or “there is a gene for Y”. (Just look at the discussion of rape in this thread — the presumption is that, if one can produce an evolutionary account of it, that explains it.)

            Generally, in evo-psych accounts of behaviour, the presumption seems to be that biology trumps culture, or that biological explanations trump cultural ones.

  24. I have a broader question. If ethology is the science of animal behavior, and there is no controversy over the claim that animal behavior is influenced by genes, and further that genes influencing behavior are objects of natural selection, then why is it controversial that the behavior of human animals is influenced by natural selection?

    Why do the evolutionary psychologists have to be so defensive when it comes to human animals. If someone wants to say that some other factor, say culture, explains all differences in human behavior among and between the sexes, it seems that they are the ones making the controversial, non-scientific claim.

    In fact, why isn’t “psychology” just considered a branch of ethology?

    1. In fact, why isn’t “psychology” just considered a branch of ethology?

      Because only humans have souls, and animals are mindless automatons blindly acting according to their physiology devoid of the benefit of Free Will.


      1. Or, alternatively, because animals don’t create Psychology Departments at universities. Or governments. Or moon landers. Or armies. Or Ferraris. Or websites (or even blogs).

        1. Or armies.

          Marching (army) ants?

          Or governments.

          Dictatorship and oligarchy are forms of government. Cue deer horse herd or wolf pack.
          Exceptionalism? [SHRUG]

    2. “If someone wants to say that some other factor, say culture, explains all differences in human behavior among and between the sexes, it seems that they are the ones making the controversial, non-scientific claim.”

      Clearly a claim that culture explains ALL differences in human behaviour would be silly. But it seems pretty plausible that human culture and our complex social structures better (or at least, more directly and succinctly) explain some behaviours than genetics does. For example, praying in the direction of Mecca is explained much better from the perspective of culture than of biology.

      Given that humans have culture in a way that is far more advanced than the vast majority of other animals, it seems reasonable to argue that an ethology of humans is going to be less successful than an ethology of non-human animals.

      NB: I agree with Jerry’s article 100% and, of course, human culture has developed out of biological and psychological features that were shaped by evolution. A wholesale denial of the validity of evo-psych is patently ridiculous.

  25. I think that evo-psych has, historically, been its own worst enemy, with researchers and advocates making grand pronouncements on the back of scant data (often nothing more than just their own “observations”, or dubious extrapolations from non-primates), and with those pronouncements often suspiciously providing a biological account for the status quo in a variety of social domains involving very nuanced and complex behaviours. (This was certainly my direct experience of the field as a psych grad student back in the day.) I am all for the field developing a far more rigorous approach, including far more careful, extensive, and cross-cultural data collection, as well as consideration of competing cultural hypotheses and how those might be ruled out. My guess is that when such proper science is done, we will indeed find that there is strong evidence for the evolved nature of some aspects of behaviour, but that the story will be far more complicated, and the behaviours far less interesting and socially relevant, than was touted at the start of the field.

    1. Pretty much what I was going post. One reason evo-psych’s been pilloried stems from some pretty awful conclusions drawn or hypotheses proposed with scant empirical support.

      I was actually rather in agreement with the earlier poster who wished that ‘psychology’ were not a part of the discipline’s title. I for one thought ‘sociobiology’ was just fine as a name, and also one that stressed the biological side of it.

  26. However bad some evo-psych theorists may have been in the past (and I don’t doubt it), I don’t think this is what explains the hostility towards it. In the past century or so, people seeking to explain human behaviour culturally – or by any means whatever – have also offered up dreadful, unsupported, ridiculous theories, and have also overreached themselves.

    1. Perhaps it doesn’t have much to do with political hostility to it, but I think it has a lot to do with the objections of many scientists.

    1. It’s actually a serious contention in feminist thought that men are stronger than women solely due to socialization. There’s a lot of seriously deranged ideology floating around women’s studies departments, and the “study” you linked to is no doubt driven by it.

      Part of the problem is that for decades, the liberal arts degrees people steeped in feminism tend to get haven’t required any kind of science education. That’s a recipe for notions and ideas about sex profoundly detached from reality. Such as another popular feminist idea – that men are just deformed women, and are on their way out of the gene pool as the Y chromosome decays into nothing.

      1. Worse, some of the “women’s studies” (but by no means all) folks are actively hostile to science (e.g. Sandra Harding) which makes things worse (though luckily this nonsense seems to be waning).

        1. Which infuriates me and I’d suspect most of the 60’s-70’s era feminists, many of whom have abandoned the term in the face of such idiocy.

    2. The bit in italics (italics mine)almost made me choke:

      “Around the world, women are on average shorter than men. Purely biological evidence suggests that it should be the opposite…”

      Where do they get this stuff from? (Actually, they tell us, and the explanation is gloriously naïve: it skips other primates, and mammals generally, altogether, and starts talking about blue whales.)

      And also, there’s something people often forget with stuff like this:

      “The mothers fed not all children immediately if they cried. It was boyish children who were fed directly, while girls kids had to wait…”

      Let’s assume this is universally true and the only explanation for the difference in sizes between human sexes (and it would have to be the former in order to be the latter). Even so, it’s most natural to interpret this genetically: mothers are genetically disposed to favour their XY offspring with food, and that’s the environmental means by sex manifests itself as size. After all, it has to be manifest by some environmental means or other.

      1. In many animal species, larger females are observed/predicted because body size correlates directly with fecundity (clutch or litter size, and/or offspring body size). So that really is the default assumption. Larger males are more difficult to explain and generally require a sexual selection hypothesis. (Ecological niche partitioning is another possibility, but as far as I know has very rarely been demonstrated.)

        1. I’m aware larger females are more common, but I didn’t think they were that much more common as to be particularly surprising. Certainly not if we exclude insects, which will bias any statistical count.

          And I also thought that in mammals, males were more likely to be larger where there was a difference. (A cursory search – only conducted after shooting my mouth off with my earlier comment – confirms this, although I’m surprised to find that 70% of the time there’s no difference in size: in mammals, that seems to be the default, which I hadn’t realised.)

      2. and starts talking about blue whales.)

        Well, whales are modified hippos.
        Hippos come from Africa.
        Hoominz cumz frm Africa.

    3. Well, we do know that diet can influence height and size (just look at pre- vs. post-War Japanese). But this particular hypothesis about male vs. female height is pretty easy to test (and disprove), in that you’d expect there to be no differences in relatively wealthy countries where food is plentiful, and I haven’t seen any studies that suggest there are not gender size differences in Western cultures.

  27. I think a lot of people have the basic, feel-it-in-their-marrow intuition that if they were made the way they are by genetic forces, that makes them prisoners; if the explanation is something else, that makes them free.

    I’ve always had the opposite feeling – which I think makes me a bit unusual – but at least being in a minority has helped me realise it’s ridiculous to take either feeling seriously.

    Like many other people I often wish we could just forget this distinction. Even a radically extreme statement like: “Every single behavioural difference between men and women is due to the way our culture is” has a hidden genetic component – it’s more or less equivalent to: “In this particular culture, XY chromosomes will result in different behaviour than XX chromosomes”. People who simply don’t like the mention of genes when talking about humans are fond of pointing out that genes don’t operate in a vacuum; but equally, culture doesn’t operate on a vaccuum.

    The correct explanation for why women are more risk averse than men, or why children are less inhibited than adults, may assign more or less work to the cultural or genetic factors, but I really don’t see why we’re so invested in the result being one way rather than the other. Maybe some of us think that if the explanation leans heavily on genetic stuff, the behaviour in question will be hard to change, and if it leans heavily on cultural stuff, the behaviour will be easy to change. But this doesn’t follow.

    Australians drive on the left and Americans drive on the right, and this difference owes nothing whatever to differences in genes or natural selection (although you’d still need to invoke genetics and natural selection to explain why people in either country can drive at all). It’s a very robust difference all the same: it would require a ridiculous amount of work to get people in either country to drive on the other side. By contrast, genetic differences are surely involved in explaining why skin cancer is more common in Australia than in South Africa – but this would be easier to change.

    1. It’s not so much that natural is equated with right and good, but that natural behaviors are much harder to change than socialized behaviors.

      So much so that if something is considered natural, you need to make a spectacularly strong case in favor of overriding that natural tendency, due to the difficulty involved. That’s why people arguing for dubious social changes try to eliminate biology from the equation altogether, claiming that the behavior or tendency in question (whatever it is) is socialized. That’s meant to directly defend against the argument that changing it would be hard – that the weak reasons provided to pursue change are insufficient to justify the effort. If you convince everyone that it’s just socialization, then change is comparatively easy, so you don’t need to make much of a case at all to justify it.

      It’s basically risk versus reward, replacing risk with difficulty of change and reward with benefit of change. Arguing over nature versus nurture is trying to skew the risk/difficulty to make it more attractive for smaller rewards.

      1. That all makes sense. I was too hasty, and I would accept that as a general (but not inviolable) rule, “natural” behaviours will prove harder to change.

        But we also need to think about what exactly we want to change. Look at height and strength…

        A social change advocate 250 years ago who said: “Nutrition is apalling – we need to make sure people get to be bigger and stronger” would have being saying something sensible. If they’d said, “Nutrition is particularly apalling among womn – we need to make sure women in particular get to be bigger and stronger” might also be saying something sensible. But someone who said: “Never mind our absolute size and strength; whatever it is, we need to make sure it’s identical for women and men” would be saying something ridiculous.

        Something similar applies, I think, to making people less violent. It migth be next to impossible to arrange things so that men are less violent than women on average. But history has shown we can reduce levels of violence, considerably. Surely it’s the latter thing that really matters.

  28. The four horseman of evo psych denial seem to be: folk-psychology, essentialism, moral oughtness, and determinism.

    One you get past the idea that our intuitions on psychology are a reliable guide to scientific theory, that we should think of men and women in these studies as two essentialist notions, that even if there are differences between the sexes that doesn’t necessarily imply anything about how we ought to treat each sex, and that even if there is such a thing as biological nature it doesn’t mean it’s fixed wholly by the genes, then assessing the merits of the science can begin.

    It’s been quite a learning curve for me to see smart people so dismissive of a science they don’t like, where those same people would be equally appalled by creationists and climate change deniers.

  29. Another point some have almost made upthread is that people are afraid to discuss differences in the sexes because of the existence sexism. I see this as similar to how people find it repugnant to criticize Islam because of the existence bigotry.

    Just as it is possible to criticize Islam as a bad idea without seeing Muslims as all bad people, it is possible to accept sexual dimorphism without proclaiming women to be bad humans.

    However, because of the taint the bad things have left (sexism, bigotry), it becomes easy for good intentioned people to see both criticism of Islam and sexual dimorphism (or even Evo-psych itself) as tainted.

  30. As someone who just began learning about evolutionary psychology, this was a very interesting, enlightening post.
    Thank you.

  31. Whatever the strict definition of evolutionary psychology in academia, in the vernacular it has taken the place of “ethology” in the 60’s and “sociobiology” in the 70’s. In other words, it means the belief that there actually is such a thing as human nature.

    Darwin certainly embraced “evolutionary psychology,” referring to evolved behavioral traits as the basis of morality and other manifestations of “human nature,” especially in his later works.

    Darwinian theories of human nature were supplanted in the 20th century by the ideologically motivated Blank Slate orthodoxy, probably the greatest scientific debacle of all time. By comparison the unpleasantness with Giordano Bruno and Galileo was a mere bagatelle.

    The most influential and effective opponent of the Blank Slate in its heyday was Robert Ardrey, who happened to be a graduate of the University of Chicago. However, today he is an unperson, because he shamed the academics and professionals in the behavioral sciences. How dare a mere playwright do such a thing? After all, what could the likes of Shakespeare, Ibsen, and Shaw possibly know about human nature?

    1. I am an evolutionary ecologist and enjoyed Robert Ardrey’s books (African Genesis, Territorial Imperative) immensely. If he missed the mark on some technical issues, his general tenor was just right.

  32. Males hunt and females do not. Then along comes some anthropologist who claims that in the tribe/band he/she studied females hunted. But pregnant,lactating, child tending females are somewhat hampered along these lines. There is about 4 million years of evolution to factor in. Males throw differently–lots of dispute over the significance of that, but they do stab and throw spears (or even rocks). Takes a bigger body. And then there is the defense role as well. There are no Amazons. Read Richard Lee’s books on the !Kung (now known as the Ju’/hoansi). Fascinating books by a fascinating anthropologist and definitely not rightwing in any way shape or form.

  33. Perhaps these gold who deny evolutionary psychology’s merits are trying to avoid being linked to social Darwinism? It seems like a pretty easy path to divert down if a particular theologian wanted to misrepresent one’s position.

  34. As an aside, sexual size dimorphism has been declining in the hominid clade. Australopithecus had a much greater sexual size dimorphism than Homo, and apparently ancestral Homo species were somewhat more dimorphic than Homo sapiens.

  35. I gather from what I’ve read here that Prof. Ceiling Cat’s professor/advisor was Richard Lewontin, a prominent Blank Slater, and author of “Not in Our Genes.” Lewontin’s professor/advisor, on the other hand, was Theodosius Dobzhansky, an opponent of the Blank Slate, who carried on a sort of subdued guerilla warfare against it in his books and other publications during its heyday. Any relevant comments or anecdotes would certainly be interesting and valuable from a historical point of view.

      1. So it would seem! There are subdued “And yet it moves,” comments all through Dobzhansky’s work, never blatant enough to bring down the wrath of the orthodox and denunciation as a “fascist,” by Ashley Montagu’s thought police, but still there, nevertheless.

        1. I vaguely remember the era; Dobzhansky of course, and I remember reading Montagu, though I had to Wikipedia him to recall what I’d read, sigh. Lewontin was already as known for his politics as his science (if I remember my OTS course gossip)…you & PCC could put me straight.

          Then as now it was sometimes uncomfortable to be a science supporter around the predominant political left. But at least said left was also concerned with peace, civil rights, etc., rather than pomo PC.

          I agree that insider dope from PCC would be fascinating, but perhaps not a socially astute move on his part at this time. ;

          (A PCC autobiography at some point would be fun, wouldn’t it?)

          1. I agree, now is probably not the time, but I would love to see a PCC autobiography at some point as well. Montagu edited a collection of Blank Slater attacks on Ardrey and Konrad Lorenz entitled “Man and Aggression,” published in 1968. It’s the most important single piece of historical source material on the Blank Slate debacle I know of, and still available used for only a penny on Amazon the last I looked.

          2. That sounds interesting! I think I can afford a penny. 😉 [Why is it worth it to anyone to sell anything for a penny?]

            I vividly remember reading African Genesis and The Territorial Imperative (IIRC those books were hugely popular at the time). And Lorenz was a hero of mine.

            Other relevant actors that PCC has known well are Wilson & Gould…

            So many walls I’d like to have been a fly on…

  36. A problem with evopsych is that there are ideologues at both ends. For every leftist who rejects the entire idea of studying these questions out of fear or disgust that one might find biological differences there is also a conservative who seizes upon any study showing differences and proclaims: therefore women belong in the kitchen, and we should get stop any attempts to increase their representation in science!

    And that justifiably ticks the first group off and makes them unjustifiably dismiss the entire field. Sadly people find it extremely hard to avoid the naturalistic fallacy…

    1. I wrote a paper for one of Mario Bunge’s philosophy of science classes years ago (~15) where I argued that his opposition to human sociobiology and evolutionary psychology was one place where he could be caught arguing from consequences.

      Curiously also Philip Kitcher does the same thing, but in a slightly more nuanced way. He claims that because our society is reactionary in the right sort of way, fields of study of certain kinds have to “get vetted” (my way of putting it) by communities likely to be impacted by the discoveries, even if in bastardized form. I have no idea how this is supposed to work because of the “basic science doesn’t lead to consequences for action directly” fact we all know – including Kitcher.

  37. I find the subject of Evolutionary Psychology endlessly fascinating and for an easy introduction I recommend “The Moral Animal” by Robert Wright available on Kindle and Audible. Otherwise simply look the subject up on the web, there really is a lot of interesting content there. Just to get you started and perhaps to spice things up a bit, try looking up the theory for gay genetic success which was posited by the late John Maynard Smith. He was largely responsible for introducing the mathematical basis of game theory to genetics. Being from an engineering background it was fairly typical of him to use somewhat salty language in describing one famous theory as “the sneaky fucker” strategy. This assumed that not all men who were assumed to be gay were completely gay and hence when the jocks, with no doubt some derision, left them behind to look after house, these “sneaky fuckers” had their wicked way with the females. This strategy is also known as the Woody Allen effect whereby the macho hunters and warriors left the more effeminate males behind, assuming assuming them to be not man enough to attract the women.

  38. When I saw the title, at first I expect critique of EvoPsych, since I considered yous site rather left-leaning and usually left-leaning guys criticise EvoPsych “jsut because”. But of course facts are not ideological, just as you have so briliantly put in the end paragraph. Kudos to the author. Rep +1 🙂

  39. The brain is a powerful complex organ bestowing benefits and failures (not enough to wipe ourselves out.. yet) on the human condition.
    A personal preponderance: Why natural selection would not make use of this fact and all things considered what is clearly a major fitness generator and not pack it (the brain) with a generalized tool kit is not unreasonable to ask.
    This is not advocating determinism (or ignoring the role of genes) genes encoded to make a big brained organism has incorporated the capacity to circumnavigate such a position as determinism. But is this capacity an unintended by product?
    If we are not a blank slate and come complete with a flexible brain for variable behaviours
    we can ask why we behave in such a way and what is it’s cause(s) i.e. the history and development of a trait over time.
    Thumbs up, this post.

  40. http://www.bsd-journal.com/content/5/1/10

    “Transcripts (2,527), many of which were linked to proteolysis, the proteasome, metabolism, catabolic, and biosynthetic processes, ion transport, cell growth, and proliferation, were found to be differentially expressed in A. aegypti female vs. male pupal heads.”

    What level of ignorance is required to look beyond experimental evidence of biologically-based cause and effect and claim that sex differences evolved?

  41. I would have more respect for those who choose to assert this theory if they were more willing to take other, related factors of biology and behaviour into consideration; but they never are.

    Perhaps male humans are larger than female humans, not so that they can compete with each other for the females, but so that they can protect the tribe; like bull elephants. Perhaps they evolved this way to kill mastodons, not to fight each other.

    Perhaps humans are more like bonobos than gorillas, and are biologically designed to be sexually promiscuous instead. Perhaps females are not the ones who are choosy about mates for biology; especially since different types of sperm have different roles; some fertilize eggs and some kill other sperm, and the balance is affected by the male’s personality. Perhaps women, like bonobos, when left to their own devices and without societal conditioning, mate with several different mates to assure that “the best sperm wins” and it is the males, in their attempt to assure that it is *their* sperm that fertilizes the egg, who wish to assure their mates’ monogamy.

    Perhaps the fact that women, on average, score ten points higher on standard IQ tests, which are designed for white, middle class men, indicates that evolution selected for intelligence in women, almost as a compensation for male size.

    But nobody ever talks about any of these factors, and that’s why perhaps it’s better to avoid the subject of sexual dimorphism and evolutionary-influenced sexual ideology in humans, entirely. Because it is far too easy to sift the facts down to use “biology” to support misogyny and “traditional marriage”; especially since contradictory evidence and other, related facts are often ignored.

    1. If men were large to protect the tribe then why men? Why not have large women to protect the tribe?

      I don’ think that the things you have mentioned haven’t been considered, it’s just that they have been considered but the evidence hasn’t supported them.

      1. Bull elephants are bigger than cow elephants because they live on the edge of the tribe and spend more time physically alone. I find it interesting that you’re speaking of “evidence” here, however. There is no more evidence to support the theories stated by the author than there is the theories I have presented (not mine, btw; this is cutting edge work of current science; I will try to find some links later.) “Evidence” would indicate that someone would have had to have conducted an experiment in isolating human societies, and since such a thing would be not only illegal but immoral, I can only assume that what we have is anthropology, compared to animal behavioural studies in primates, and juxtaposed onto our biology and genetics in a “reverse engineering” sort of way; which is, ultimately, speculation. *Intelligent and educated* speculation, yes, but speculation nonetheless. Bias of the observer gives weight to some pieces of data more than others, and until very, very recently, the feminine (and feminist) perspective was not an option in biology. Or psychology. Or field of science, really. So I don’t believe it has been thoroughly considered; though I will own, these theories are newer.

        1. And human males aren’t anything like bull elephants and don’t spend time alone on the fringes, guarding tribes. It’s just not how human societies work.

      2. “If men were large to protect the tribe then why men? Why not have large women to protect the tribe?”

        One of the most widely accepted assumptions in this field is that the reproductive investment of women is so enormously greater than that of men that we’re already “burdened enough.” And men have to have something to do… 😀

        Although the world would look quite different had our species gone the way of, say, some fish, in which the male became basically a miniscule sperm-providing parasite of the female…


        1. Although the world would look quite different had our species gone the way of, say, some fish, in which the male became basically a miniscule sperm-providing parasite of the female…

          That’s fishandry!

          1. That wiki page acknowledges that it has issues. The text says human top, fishy bottom when in fact the picture has him reversed. And shouldn’t he at least be wearing some kind of Speedo?

          2. Ah, shit — I just got back from a quick trip to Whole Paycheck and forgot to get any artichokes. Why didn’t you write this post earlier this afternoon!?


          3. Not bad stuff with which to make do:-). Also had some avocado w jicama tonight. I’ll be our across the Pond friends don’t know from jicama….

          4. Yum!! Gotta write that combo down. Love papaya, too. Might add a grating of fresh ginger.

            It’s fairly easy to find here at WF and some of the other better stores but the checkout kids never know how to pronounce it.

          5. Wish I had a back 40!

            The closest we’ve got in the back yard are fence lizards (and grasshoppers and the like).

            …and you’re thinking of Texas, which is about five hundred miles to the East. No armadillos in the Sonoran Desert, not that I know of. Gila monsters, yes…but I’ve yet to see one in the wild. And roadrunners and coyotes. But no armadillos.


          6. Yeah, the proportions are off. Roadrunners are good sized birds…bigger than pigeons, smaller but longer than chickens. And coyotes aren’t terribly large…medium-large for domestic dogs, smaller than many German Shepherds. But there’s still much more difference in size between the two species than the cartoon shows.

            …then again, not much else in the cartoon has much bearing on reality, either, of course….


          7. Ah, now wait:

            “…then again, not much else in the cartoon has much bearing on reality, either, of course….”

            What about the psychological dimension? Audiences everywhere identify.

    2. But how would this follow?

      So there’s a difference. What does that tell you normatively? Nothing: we can decide to do all sorts of things about difference: help out those who may suffer because they lack something; we can ignore it; we can work to prevent discrimination against those who lack, etc.

  42. If females select on average larger males to mate with and thereby perpetuating sexual dimorphism, this seems to be bordering on a case for sexual selection.
    Selecting for fitness or simply a fashion, a female preference for bigger men has benefits for females, especially when life spans were lower, disease, general security food supply would be a factor in a mating strategy, sexual dimorphism is maintained for the time being.
    Division of labour after agriculture started would have also contributed to sex size differences.
    With better diet good nutrition, we are taller on average today which would also mean more body ass body mass comes with it, making bigger bodies not just in males.
    On the whole females still prefer males bigger than themselves, our deep Darwinian past is not so far away.
    Evolutionary psychology is not about determinism although I believe no behaviour is exempt from gene influence, somewhere in the chain, how much? who knows.
    But when it comes to observable behaviours it’s cause and function, these can have answers which reveal our past and hopefully lead to understanding the present.
    If self knowledge is the goal this is one more tool.

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