Evolutionary psychology, demarcation, and grand unified theories

Last week evolutionary psychologist Satoshi Kanazawa published the highly controversial “Why Black Women are Less Physically Attractive Than Other Women.” I’m not interested in debunking his claims (that has been done quite ably elsewhere). Instead, I’ll add my two cents to a debate that cropped up on TNC’s blog. Should we consider evolutionary psychology a science? And why does it seem to repel people and is open to “hucksterism?”

I’ve discussed the science versus not-science distraction with respect to economics, and I think a similar analysis also holds here. What matters is whether a particular piece of ev-psych research is good scholarship, not whether the field as a whole can be classified as “science.”

The second question is far more interesting, and one that I’ve been meaning to blog about for a while. I think ev-psych, with its grand theorizing on how evolution explains everything we observe today, can sometimes display really bad physics envy. Outside of physics, it’s often not possible to explain all phenomena with a single set of laws. Some would argue it’s not even possible in physics.

At any rate, here is the comment I left over at TNC. Of course I quote Natural Reflections at the end!

Frankly, I don’t think we should even be trying to ascertain whether ev-psych is “a science.” That question is too vague to be meaningful. What we should be doing is determining whether a particular claim is backed up by sound evidence, strong analysis and general good scholarship. Being officially considered “science” should almost be besides the point. Some research is very weak and must be taken with a grain of salt even if it is lucky enough to be labeled science. I would put much biomedical science in this category. On the other hand, some historical scholarship (e.g. the role of blacks in the Confederacy) is bolstered by reams of supporting evidence. We rightly trust such work even though historians aren’t considered scientists.

It’s important to note that apart from the opening paragraphs, Ryan spends almost no time questioning the scientific status of evolutionary psych writ-large. Rather, he meticulously and carefully demolishes Kanazawa’s specific research. That’s the approach we should always try to use. In this case, Kanzawa’s work is crap whether or not we deem it science. And since, as Ace Rock shows above, certain aspects of ev-psych do have explanatory power, it makes no sense to offer either blanket praise or condemnation for the field.

As for ev-psych’s being open to hucksterism, I attribute part of the problem to the false seduction of grand unified theories. That is, we’re always trying to find the single theory that will explain everything about everything. Physicists have been very successful at this, and I think other scientists sometimes unfortunately take a similar approach. But once the question gets very hard (basically anything that can’t be described perfectly with math, which is basically everything humans care about), we’re left with the rather boring, mundane statement that we need many different factors working together to explain anything.

I think that many intuitively grasp this concept–that complicated phenomena don’t have single-cause explanations. And so when they see some evolutionary psychologists boldly claiming that they have found the reason for such and such phenomena, people get understandably annoyed.

Along these lines, I strongly recommend Barbara Herrnstein-Smith’s “Natural Reflections.” While the book is about science and religion, she does an excellent job eviscerating the strong interpretation of ev-pysch. From page 66:

In seeking to account for any complex behavioral, cultural, or social phenomenon, a good starting assumption would be that it was the emergent outcome of multiple factors of various kinds, operating at many scales and levels, interacting over time.  The starting assumption of evolutionary psychology and “cognitive” approaches to religion, however, is that the best way to explain any behavioral, cultural, or social phenomenon is by demonstrating that it is the outward effect of the activation of some underlying mental mechanism.  A methodological tradition of this sort puts a premium on ingenuity with respect to the hypothesizing of mental mechanisms and, by the same token, encourages negligence with respect to the investigation of possibly relevant environmental, experiential, and developmental factors.


  1. Hi Praj,

    I think many fields of the life sciences have physics-envy. But the main reason I wanted to comment is because I’m starting a science policy blog and I think you might be interested, or at the very least, have some helpful advice for me! Thanks!

    1. Hey Marci! so good to hear from you. It’s awesome you’re starting a blog. I’d be glad to chat and offer you my limited advice. I’m pretty new to this myself! Why don’t you drop me an email? pxk161 at gmail dot com.

      Have a good memorial day.

  2. Excellent thoughts here, Praj. I’m with you on all of it. I definitely think that it’s a better strategy to evaluate specific claims rather than debate about whether ev-psych is a science or not.

    Some of the most scathing criticisms of ev-psych have come from within the psych discipline–from social and cognitive psychologists. The critiques usually focus on the fact that an important aspect of science is falsifiability, and that many ev-psych explanations for human behaviors are unfalsifiable. Usually, when psychologists find human behaviors, they test different mechanisms to see whether the mechanisms explain the behavior. But because the mechanism in many ev-psych effects is a story about stone-age humans, the mechanism is often untestable, and then it just boils down to who can tell the best story of why a stone-age human would behave in the way that we observed (this is the “just so stories” criticism).

    Along those lines, another charge against specific ev-psych studies is that they sometimes have low predictive validity–in other words, the usual process is to find an interesting effect, and then construct a back-story to explain the effect rather than coming up with a story first and then testing it. To be fair, a lot of social and behavioral science studies suffer from these poor practices as well, but ev-psych studies tend to get hammered on the most.

    1. Hey Omair! Good seeing you this past weekend. Thanks again for the comment. I agree that a lot of social and behavioral sciences suffer from poor practices. But I would say that’s b/c the problems are often much harder than those in physics, e.g.

      I like your description of the back-story process of ev-psych. I had heard that before, but not articulated that way.

  3. What is it about arrogant physicists that they think everyone wants to be like them? Puh-lease! (huge eye-rolling)


    I agree with you on being skeptical of grand unifying theories and being cautious about throwing the baby out with the bathwater on ev psych. Any well-executed science is a useful contribution, IMO, and there are many areas (parts of psychology included) where that is rather unfortunately, the minority of studies. If nothing else, I think the mere presence of ev psych is useful because it encourages interdisciplinary collaboration and new approaches to psychology and biology which can result in exciting directions if not results.

    We’ve been away, so am just catching up on your blog now after several weeks!

    1. Welcome back! If I wasn’t clear above, I wish fewer people tried to be like me:):)

      In all seriousness, I have heard other scientists (neuroscientists and economists specifically) themselves say their field tries to imitate the reductionist approach in physics. And that’s what I was referring to.

      At any rate, thanks for your comment! I hadn’t thought of the interdisciplinary benefits of ev-psych.

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