Evolutionary psychology, sexual dimorphism, and ideology

Why Evolution Is True

(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?


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

  1. I don’t know why males are bigger and stronger, but it seems so obviously true to me that I wonder at people who can deny this. It also seems clear that women on the whole are attracted to bigger, stronger men.

    I read through a part of the thread and noticed that quite a few short women preferred very tall men, 6 ft or greater even. A taller woman complained that the short women should leave the very tall men for them. It was a joke, but there’s something interesting about it. The taller, stronger women want a man who’s taller and stronger than they. There is no desire for equality here.

    I find it fascinating that even the very short women want a very tall, strong man. It’s not a matter of having a man who is a little stronger and taller, not a matter of having a man who’s sufficiently strong. I can’t quite understand this from a personal perspective, although from an evolutionary perspective it makes sense. I wonder if there are studies on women’s preferences not just for stronger and taller, but strongest and tallest?

    From a personal perspective, I have to admit that having a man who’s somewhat stronger and taller than me is important, but being 5 feet tall and on the weak end of the spectrum even for women, I don’t have to look very hard. I don’t share that desire to have the strongest and tallest (and I don’t mean this rationally, but as sexual attraction). I’ve just always been attracted to those who won’t give me a crick in my neck. 🙂 But I suppose there are always exceptions to the rule, always people like me who have to deviate from evolutionary trends.

    Liked by 2 people

    1. Interesting thoughts. Sexual selection is a tricky phenomenon. It doesn’t always lead to the mate with the highest potential for survival. (The peacock tail comes to mind, possibly a result from an evolutionary “arms race” over an attribute that did once signal increased survivability.) And there are always a range of preferences, although the species overall will tend to move in the direction of the attributes favored by most.

      I agree with Coyne that evo-psych shouldn’t be dismissed, but we have to be cautious. Anthropologists will point out how dependent many of our intuitions of sexual attractiveness are on culture. The challenge of sussing out evolutionary inclinations from cultural ones shouldn’t be underestimated.


        1. It can be tough. The main strategies are looking at other species of primates and looking for behavior that is universal across disparate cultures. Social psychologists a few years ago realized that most of their conclusions were based on studies of undergraduate college students. They now try hard to avoid WEIRD (western, educated, industrialized, rich, democratic) biases. It’s much more expensive than simply studying their undergraduates, but sites such as Mechanical Turk are making it easier.

          Of course, skeptics will say that even going cross cultural doesn’t guarantee that you’ve found an evolutionary inclination. You might have still just found one that exists in most cultures. But it seems like the more cultures in your study sample, the higher the probability is that you’ve identified an aspect of human nature and not just culture.

          Liked by 1 person

          1. There’s the problem that these cultures didn’t evolve in a vacuum, either – almost every culture on Earth has had mass exposure to the ideologies, beliefs, and practices of a handful of powerful cultures over the past several centuries. It’s sort of like pointing out that hunter-gatherer societies of the distant past are not necessarily the same as those of the present, since those of the present are survivors living on the margins of settled society.

            Just think about how thoroughly changed all indigenous American cultures were by interaction with Europeans.


    2. A taller woman complained that the short women should leave the very tall men for them.

      As a dude of below average height, who prefers women a bit shorter than himself: I concur with the tall woman. 😉

      Liked by 1 person

  2. 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.

    They don’t dismiss that, they’re just skeptical of the often-lazy way that evolutionary psychology claims are used to rationalize whatever exists at the moment in terms of human behavior due to weakly verified claims about the environment that our ancestors supposedly lived in.

    As for his claim, isn’t it potentially challenged by Bonobo behavior? Bonobos also have sexual dimorphism, but they don’t have the more aggressive mate competition among males.


    1. Evo-psych skeptics come in different flavors. Some do deny the theoretical foundations (PZ Myers comes to mind). Others (such as Massimo Pigliucci) are more careful and are more in line with your views. I actually share those views, but I do think there is good evo-psych work going on. Every field has its weak practitioners. If we dismissed an entire field for those contingents, we would pretty much have to dismiss all of them.

      That said, I do agree the evo-psych field is too lenient with members who only hypothesize just-so stories exerting little or no effort to actually test those hypotheses. As with economics (and physics if it isn’t careful), these ideologues get too much attention, and undermine the credibility of those who are actually doing rigorous work in the field.

      On cultural universals, given the still wide range of cultural mores, couldn’t we agree that a psychological trait found across those disparate cultures is more likely to represent an evolutionary instinct than a culturally specific one? I’ll definitely grant that we can’t know for sure (unless maybe it also existed in other primates), but all knowledge is probabilistic, and sometimes we have to take what limited certainty we can get.


      1. Maybe. Like I said, the whole thing’s been thrown awry by the power of a handful of cultures over the past 500 years – that makes it hard to tell whether something is a universal or simply something they’ve assimilated from a more powerful neighbor.


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