The substantive issue in the evolutionary psychology debate: innate difference between men and women

Well, not the only substantive issue, but possibly the main one raised by Rebecca Watson’s Skepticon 5 talk. Ed Clint’s post actually did a good job of concisely summarizing the issue, but it’s to paragraphs in a long post so let me pull them out:

Evolutionary psychologists only lean heavily on non-controversial facts about the past. For example, pregnancy involves numerous costs, and we therefore expect that females in many species will be more picky about mating than will males. This prediction has strong empirical support for both humans and other animals. Source


EP theories must make testable claims and do so. Example: Robert Trivers predicted that, among all animals including humans which have two sexes, the sex with the greater minimum investment in offspring should be more sexually choosey and the other more sexually aggressive/promiscuous. A comparative study of animal behavior could easily disprove his theory, though it has been confirmed by many observations.

Trivers’ original paper can be found here; a more recent paper with a good discussion of the issues and the results of a cross-cultural survey on desire for sexual variety can be found here. Note that the claim that women are more choosy about sexual partners than men are is not the claim that “women hate sex,” which Watson attributed to evolutionary psychologists in her talk. I, for one, am quite confident the first claim is true but equally confident that the second claim is false.

It would be interesting to hear Watson (and Stephanie Zvan, PZ Myers, and everyone else in the skeptic movement whose set themselves up as a critic of evolutionary psychology) explain what they think of the above paragraphs and papers. They certainly seem to make interesting claims, and since Watson claims that any good evo psych would be boring, it seems she’s committed to claiming none of that is good evo psych. But if that claim was merely misleading, this would be a good example to use clearing that up.

One thing that may be going on with some members of the anti-evo psych crowd is that they recognize that Trivers isn’t on par with Kanazawa–but they don’t think there’s much difference, so they don’t think there’s any need to be terribly careful distinguishing between the two. But if that’s what they think, they should say so.

  • Yvain

    I have a huge amount of respect for you for being brave enough to address this issue and for doing it so rigorously and well and I’ve really liked your last few posts here.

    On the other hand, I kind of wish you hadn’t posted this one. I think part of the problem is that politically controversial evo psych is “sexier” and so the only thing most people see, which leads to people like Rebecca not knowing that there’s this whole field of well-grounded evo psych that doesn’t have much to do with politically charged topics at all. Arguing “But we’re right about the politically charged topics!” is true. But if you’re one of the few people in a position to reach these skeptics, do you worry that reinforcing the disproportionate focus on the politically-charged topics might be dangerous?

    • Chris Hallquist

      Hmmm… I didn’t quite look at it that way.

      Way I see it, trying to talk around the real source of the dispute is likely to just make things more personal, invite more of the “that’s not what she was talking about why are you even talking about that you just must hate her” responses.

      That’s why I don’t plan on responding, for example, to PZ’s latest, since I think more than a couple rounds on those kinds of issues aren’t going to get us anywhere.

      Granted, I could do a post series just explaining interesting bits of evolutionary psychology, without even trying to directly address the controversy but (1) not sure it entirely avoids the elephant-in-the-room problem (2) hard to get people to pay attention, see where people like Watson go wrong without directly pointing it out (3) for the people who always say the evidence is ambiguous, I actually the evidence is unusually clear-cut.

      On (3), for example, where is the nice tidy test of Trivers’ theory of self-deception that keeps making the right prediction in species after species? That’s the kind of problem you run into.

  • Andrew G.
    • Edward Clint

      Posting this PLOS paper without comment suggests you believe it is self-evidently refuting. It is not. It is a purely theoretical paper; it’s authors have done no original tests of it and they have no original data. They also cite other theoretical papers about potential new models equally untested. Now, these could all turn out to be great new advances or sound critiques to current EP. But right now, they are, at most, interesting speculation.

  • almost ambitious

    I think it’s great that you’re doing this series because there seems to be a tendency to conflate media reporting of evo-psych with the whole of evo-psych. This is certainly what RW seemed to be doing but it was worrying how little research she’d done before speaking; my only exposure to evo-psych is through proof-reading psychology essays and even I could tell that some of the stuff she was saying was blatantly wrong.
    There seems to be an underlying idea in skeptic communities that we’re better, or at least more academically rigorous, than religious groups because we argue from principles of logic and evidence. RW wasn’t doing this in her talk and it is problematic because as a well known skeptic she should be modelling good arguments for people new to the community, or outsiders looking in, or just those of us who don’t have that much experience in constructing good arguments. That said, a lot of us could stand to remember that ad hominem attacks (however much they’re deserved) also constitute logical fallacies.

  • miller

    I think of all the evidences presented for EP, cross-species studies are relatively persuasive, at least to me. It solves the problem of creating ad hoc theories to fit your data, because you would have to make different predictions for different species. However, that still leaves me unconvinced by all the EP hypotheses which are not supported by cross-species studies.

    • Edward Clint

      I used such a method in my latest paper- to good effect I hope. However there are some limitations. You can’t study anything uniquely human with cross-species studies, such as language or social contract theory. I think those topics are worth studying and that alternate methods can shed light on them.

      • MichaelD

        Or more broadly there’s also the problem you see in medical research. As it was put to me in one of my classes “Mice aren’t people”. So anything you find in other animals may not necessarily apply to people. Hence why you ultimately have to test your drugs in people and the same should hold true for EP.

  • J. Goard

    Still no mention of the elephant in the room, eh?

    The situation we find ourselves in at the moment is not about some idiosyncratic intellectual failings of Watson, Zvan, Myers, or any single individual in the atheist movement. Rather, it’s about science denialism institutionalized within the humanities and social sciences. The smug, incurious and dismissive attitude of Watson in her speech is precisely the attitude that thousands of antro, social psych and “[x] studies” undergrads are receiving from their professors right now. And the potential threat that this science has to those professors’ legacies is far from trivial.

  • jose

    So I’m reading Trivers’ paper. The conclusion says that parental investment is a predictor of how individuals go about mating, so by studying parental investment we should get an idea what to expect when it comes to sexytimes. Then he describes what happens in the cases where male invest less than females and also what happens when both invest equally, as well as what should happen when males invest more. All three cases are covered. He does mention the vast majority of animals have hardly any male investment. Then again, the vast majority of animal species are arthropods. Not sure what the relevance of shrimp reproduction might be to the topic at hand, namely sexual desire in humans.

    What he didn’t say is what kind of parental investment / sexual behavior we should expect in any given species, such as the Anolis lizards he studied, or, say, humans. For example, he mentioned some species of frogs that showed more male investment. He did not use data from other frogs to predict that these frogs should show mostly female investment and therefore mostly male promiscuity (he would have been wrong); rather, what he did was to show that his parental-investment-as-predictor idea explains the additional field observation that indeed females of these species initiate the mating more frequently (and again, not sure what frog reproduction might say about sexual desire in humans). For this reason, Ed Clint’s leaning on this paper is misplaced because it doesn’t support the inference into humans he makes. It doesn’t support any inference of what sexuality should be expected to look like for any given species.

    Also, um, the most frequent sexual activity in bonobos is females rubbing each other. Females also masturbate more than males. Also, most sex happens when females are not fertile. But that’s only if we don’t limit our view to what the judeo christian tradition opines sex is. I’m afraid a study of sex whose only concern is “penis-in-vagina-and-ejaculation” is going to miss a lot of what’s going on. Incidentally, they’re more related to us than shrimp. Then again, chimpanzees are just as much related to us and their sexual behavior is extremely different to that of bonobos and also to that of humans. Then you have gorillas next on the list, and they’re also very different from all our bonobo-chimp-human sub-branch. Unfortunately I don’t know anything about orangutan sex, so I can’t go on (shame on me). In any event, things are a little more complex than that.

    Now, onto Watson:
    …”since Watson claims that any good evo psych would be boring”

    That’s sarcasm about how the studies that usually make headlines in pop science magazines are wildly overblown, just a bit of good old sensationalism in the good tradition of journalism: let’s pick the controversial ones, let’s create interest. After all, it was published, so it must be good enough, right? Back to Watson: it’s not “I personally would consider them boring”, but “they would be too boring for publication in popular magazines given their preference for wild exaggeration, so it wouldn’t get into the mainstream and make an impact on society’s view of what “science” says about women, which is the bottom line of my talk.” A little bit more nuanced than you thought, but it’s clear enough even for a non native speaker like me.

    • Reap

      If she doesn’t find it boring then why couldn’t she provide a resource to anything she was talking about? If there is anything she should be able to do it is to give some kind of suggestion of where to learn more about the subject she has just spent an hour talking about.

  • J. Goard

    “Not sure what the relevance of shrimp reproduction might be to the topic at hand, namely sexual desire in humans.”

    Then you’re missing the point entirely.

    Suppose a researcher were interested in the relationship between extreme obesity and disease. Such a study might reasonably look at the epidemiological data from subjects of all body sizes, down to the very slim. Would it then make sense for somebody to say, “not sure what the relevance of thin people’s health might be to the topic at hand, namely disease in the morbidly obese”?

    • RowanVT

      Of course not, as having thin people would give a baseline from which to gauge the effects of obesity. But they are the same species. If you add in fat dogs and cats and primates, then they’re all at least still mammals. Add in birds and reptiles and fish, at least they’re all vertebrates.

      The systems of non-vertebrates, however, are rather different than vertebral ones. How does the extra weight affect respiration? Oh wait… they don’t have lungs. How does the extra weight affect bones? Oh wait….

      Those studies would have done better to stick to mammals and *maybe* include birds because of their pair bonding. Using shrimp is only one level better than using coral.

    • jose

      So, shrimp reproduction is important for human sexual desire because the metabolism of thin people is important to study obesity? Is that your argument?

      • J. Goard

        No, geniuses, the point is that if you’re the relevant variable is relative parental investment, and the hypothesis is that higher necessary investment will show a positive correlation with higher choosiness in mates, then it is hardly irrelevant to look at many diverse species.

        • J. Goard

          Note that this is a question of fundamental principles of natural selection, not an attempt to catalog an idiosyncrasy that has appeared in one particular clade.

        • jose

          Already addressed: “What he didn’t say is what kind of parental investment / sexual behavior we should expect in any given species”. From last comment. The point of the paper is that once you have studied parental investment in a specific species, you can to some extent predict promiscuity in that species. Not before. So you need to study parental investment in humans first and find its genetic component (not sure how you’d go about doing that; literature on parental investment is predominantly anthropological and those guys are big on the “nurture” part of the dichotomy) and then you can use Trivers’ paper and see if it holds up.

          • J. Goard

            First, you don’t need to “find its genetic component” to have something important to say, unless you think that everything Darwin wrote about evolution was equally useless (since there was no genetics).

            Second, do you need to consult anthropologists to know that a human male can produce a biological child by depositing sperm in one act of intercourse, while a human female must consume a large amount of extra nutrients and (before very recent medical advances) undergo considerable risk to life in order to reproduce? This is what evolutionary psychology means by assuming a difference in parental investment. Do you think it’s rational to disagree with that?

          • jose

            - Darwin tried to tackle the problem of inheritance without success, that’s why he didn’t rely on genetics. He knew there must be a system of inheritance because of obvious traits (kids look like their parents for instance) and he treated it as a black box. But we have more resources available these days than Darwin had, so we know traits that are passed on throughout generations have a genetic component to them. That’s what you actually do when you determine some trait is in fact inherited, you’ve measured its genetic component. Simply, I can talk genetics because we know genetics; we don’t need to treat it as a black box anymore. I’m sure you know all this, so my guess is you’re just attempting to nitpick now. Don’t be that guy.

            - That’s a step in the right direction, taking a look at humans in order to study humans rather than relying on other distant species. Still, what you describe -males limiting themselves to fecundation- is not really what happens with us humans, is it? If you know your father at all, you know it is not the case. Your picture is incomplete. But that’s the right track: study parental investment in humans. That’s why I mentioned anthropologists: they are the ones doing the research on that. I’m afraid things are a little more complex than sweeping assumptions of the kind you hold.

          • J. Goard

            I responded to your dismissal of certain research into evolved mechanisms on the grounds that the “genetic component” hadn’t been identified, and you think this is “nitpicking”? Very much to the contrary, that kind of thinking would doom nearly all of biology, and very much of science in general.

            For example, off the top of my head, it would be fairly easy to do a proper scientific study about the effect of room color on test performance without requiring any knowledge of what hypothesized differences might look like in the brain. The fact that we have developed brain scan technology and more sophisticated neuroscience doesn’t in any way invalidate the huge number of psychological studies that manipulate environmental variables and measure behavior. Similarly, I imagine that food science researchers are able to conduct properly controlled tests on the efficacy of certain preservatives for limiting the growth of microorganisms, without having to know the specific low-level causes in the biology of each possible organism that result in the observed effects.

          • J. Goard

            “Still, what you describe -males limiting themselves to fecundation- is not really what happens with us humans, is it? If you know your father at all, you know it is not the case. Your picture is incomplete. But that’s the right track: study parental investment in humans. That’s why I mentioned anthropologists: they are the ones doing the research on that. I’m afraid things are a little more complex than sweeping assumptions of the kind you hold.”

            None of your ridiculous depiction of me here makes any sense. Of course I don’t assume that ancestral males usually knocked up females and fled the scene, and no evolutionary psychologist does either, apart from the straw man in your mind.

            It’s you that are deeply confused. You still don’t seem to appreciate that when evolutionary psychologists feel safe in assuming a differential in “parental investment”, they’re not assuming anything about later child-rearing effort. What they’re assuming is the huge non-optional costs in pregnancy, childbirth and nursing for a female to have viable offspring. And, as I said above, we have no need for anthropological research to conclude that this major difference between males and females was present all throughout our evolution.

  • Becky Transsexual

    I’d argue that P Z Myers has bought into the ‘innate differance between men and women’ as espoused by the heterosexist transphobic sexists, though. In my own personal experience, the way he treats transwomen and those who ‘gender transgress’ against the patriarchal rulin elite of which he is a part of and who have the ‘temerity’ to disagree with him suggests that.

  • MNb

    Here you have something to chew on:

    I’d like to read your comments as I know about zilch about the subject.

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