Evolutionary psychology for the tyro

March 21, 2023 • 1:15 pm

UPDATE:  I found an old post from 2012 in which I singled out areas in which evolutionary psychology was making progress.


I’m presenting this post as a public service for those who have, by lurking in certain dark and nescient corners of the Internet, heard incessant dissing of evolutionary psychology.  Those are the toxic places where you hear stuff like this: “The fundamental premises of evo psych are false.” Along with that goes a mantra born of ignorance: “Evolutionary psychology simply makes up post facto adaptive explanations for all human behaviors. It’s just a game.”  Then they’ll mention something like girls being dressed in pink because in our ancestors, women collected red berries.

People like this haven’t kept up with evolutionary psychology, which is reaching maturity as a discipline. Sure, there’s been bad evolutionary psychology, and an all-too-easy reliance on just-so stories. But every aspect of evolution has been plagued by adaptationism.

But now Laith Al-Shawaf, an associate professor of psychology at the University of Colorado at Colorado Springs, has written four distinct but related essays on why we have to take evolutionary psychology seriously.  One of the main points of these pieces is to show that evolutionary psychology is no longer mainly concerned with confecting explanations for human behavior, but now is engaged in predicting what we expect to find about human behavior before those observations are made.  And, sure enough, he cites a lot of cases where evo psych has enlightened us about the source of our behaviors. Further, it’s raised new questions that themselves can be tested—the mark of a progressing science.

This is a resource, so I won’t summarize what each essay says: I’ll just give a link and a few excerpts. The point is to give you enough ammunition to counter those who have written off the whole area as useless—as a swingset for playful minds.

The first essay dispels misconceptions about the field; the short second essay reprises Mayr’s distinction between proximate explanations for behaviors (i.e., the mechanism that produces them, like a surge of hormones) versus ultimate explanations (the evolutionary explanation; why those behaviors came to be); the third (and meatiest of the pieces) gives a boatload of examples where evo psych made a priori predictions that were verified and thus produced new insights; and the last essay, in Psychology Today, summarizes a few examples of behaviors that don’t make sense except (as Dobzhansky said) “in the light of evolution.

As Al-Shawaf says, the essays need not be read in order. Were I to pick the most important two, it would be #1 and #3, especially #3, which is full of references to studies.

Essay 1: Misconceptions about Ev Psych:(all except the last are in Areo)

The point of this essay is not to suggest that evolutionary approaches to psychology are perfect. They are not, and there is certainly room for improvement. However, the widespread misconceptions discussed in this essay have impeded the field’s acceptance among both academics and the general public. And given that these concerns are largely unfounded, many people’s rejection of evolutionary psychology has little to do with its actual merits and limitations, and is predicated instead on a foundation of misconceptions.

Perhaps more importantly, these misconceptions impede the progress of psychology as a whole, because the science of mind and behavior cannot reach its full potential if it ignores evolution. There is simply no escaping the fact that our brains are a product of evolution, and that this has important consequences for how our minds work.

Essay 2: Proximate & Ultimate Levels of Analysis

This point refutes the quotation in the first paragraph:

Why would the explanatory partitioning of phenomena into different levels of analysis apply only to biology, and not to psychology? Just like the heart and the liver, aspects of the mind are subject to the same four questions: how they develop during the organism’s life (ontogeny or development); how they work in the present moment (mechanism); how they evolved over time (phylogeny); and why they evolved (function).

Scientists have long known that they cannot skip either the proximate or ultimate level of analysis if they want a complete understanding of our bodily organs. The same goes for our mental organs—if we want a complete understanding of, say, attention, memory and emotion—we will need to address these aspects of the mind at both the proximate and ultimate levels of analysis.

This does not imply that every aspect of our minds has an evolved function. As evolutionary psychologists will tell you, our minds contain plenty of byproducts (side effects) that have no evolved function. But even these functionless byproducts require the ultimate level of analysis: they have evolved over time (so they require the phylogenetic level of analysis) and are byproducts of adaptations that have a biological function (so they require the functional level of analysis). There is simply no way around the conclusion that the ultimate level of analysis applies to the mind and how it works.

Note that Al-Shawaf freely admits that there are byproducts in the mind and in behavior: side effects of evolved traits that weren’t directly favored by natural selection. Evolutionary psychologists no longer spend their time finding random human behaviors and making up reasons why they could have been favored by selection, and then dusting themselves off and saying “job well done!”

Essay 3: Predicting New Findings

A common refrain in the social sciences is that evolutionary psychological hypotheses are “just-so stories.” Amazingly, no evidence is typically adduced for the claim—the assertion is usually just made tout court. The crux of the just-so charge is that evolutionary hypotheses are convenient narratives that researchers spin after the fact to accord with existing observations. Is this true?

Do Evolutionary Approaches Lead to New Predictions? What About New Discoveries?

In reality, the evidence suggests that evolutionary approaches generate large numbers of new predictions and new discoveries about the human mind. To substantiate this claim, the findings in this essay were predicted a priori by evolutionary reasoning—in other words, the predictions were made before the studies took place. They therefore cannot be post-hoc stories concocted to fit already-existing data.

There are tons. Here’s just a sample for one of several behaviors or emotions:


It isn’t just anger, of course—evolutionary theories offer similar predictive power in other areas of psychology.

Consider the following evolutionary predictions about disgust, all of which were made a priori: 1) people’s disgust will be more strongly triggered by objects that pose a greater risk of infection, 2) women will be more disgusted during the first trimester of pregnancy compared to the second and third trimesters, 3) people who grow up in regions of the world with higher levels of infectious disease will be less extraverted, less open to new experiences, and less interested in short-term mating than their counterparts who grow up relatively pathogen-free, 4) cross-cultural differences in pathogen prevalence will predict cross-cultural differences in individualism-collectivism, 5) those with a stronger proclivity for short-term mating will be less easily disgusted, 6) experimentally triggering disgust will reduce interest in short-term mating, 7) people will feel less disgust toward their own offspring and their offspring’s bodily waste compared to the offspring of others, and 8) presenting people with the threat of disease will cause a host of psychological and physiological changes that reduce the likelihood of infection, including a) releasing pro-inflammatory cytokines, b) behaviorally withdrawing, c) temporarily becoming less open to new experiences, and d) reducing one’s desire to affiliate with people. All of these predictions were generated before the fact on the basis of evolutionary reasoning, and all were subsequently supported by the data.

Note that some of these findings could probably have been predicted without evolutionary reasoning. For others, it would have been harder. And for others still, it would have been nearly impossible.

The crucial thing, though, is that at no point in any of these examples is an evolutionary explanation being concocted post hoc to accord with existing data. In each case, evolutionary reasoning is being used to generate a novel hypothesis—and this hypothesis is then tested, leading to new findings. In other words, we are not moving from known observations → convenient post-hoc explanations—we are moving from evolutionary reasoning → new a priori predictions that get tested, leading to → new discoveries about previously unknown phenomena.

Notice how starkly the above evidence conflicts with the just-so allegation. The crux of the “just-so” charge is the idea that evolutionary hypotheses are plausible-sounding stories that researchers concoct after the fact to accord with known observations. But the examples in this essay—which are quite standard —show the charge to be woefully misinformed. Evolutionary hypotheses in psychology stick their necks out on the line, making clear a priori predictions that are then tested and either rejected or supported by the evidence.

Essay 4: Explaining Known-But-Puzzling Findings:

As it turns out, a great many findings in the social and cognitive sciences don’t really make sense except in the light of evolution. For example, evolutionary thinking helps explain why our dreams include specific sensory modalities and why our bodies are vulnerable to disease. Without evolutionary theory, it would be difficult to make sense of the Coolidge Effect in male animals. Specific mate preferences, such as for facial symmetry or deep voices, would seem arbitrary and inexplicable. Evolution yields insights about topics in psychology and behavior as wide-ranging as maternal-fetal conflict in the womb, conflict between children and parents over the children’s mating decisions, why personality differences are heritable, why psychopathy hasn’t been filtered out of human populations, why we crave foods that are bad for us, why suppressing fever can be harmful, why ostracizing someone is one of the most agonizing things you can do to them, why Taiwanese “minor marriages” are plagued with sexual and romantic difficulties, why male aggression peaks during the teen and young adult years, why humans have an “auditory looming bias” that applies to harmonic tones but not to broadband noise, why indirect speech has the characteristics that it does, why mental disorders have the features they do, why coalitional psychology works the way it does, and why non-infectious objects sometimes trigger disgust.

Crucially, the claim that evolution helps explain these phenomena does not imply that they are all adaptations. Many of the explanations linked above are distinctly non-adaptive in nature.

Equally crucially, please don’t fall into the common trap of thinking that evolutionary reasoning can only be used to explain known facts, but not predict new ones. There are hundreds of examples of new predictions (and discoveries) generated by evolutionary approaches to the mind. A few dozen are described here.

So there’s your evolutionary psychology primer. The articles are short; I’d recommend reading one at bedtime each night. They will serve as your Pasteur-ian inoculation against the nipping of rabid dogs who know nothing about modern evolutionary psychology but oppose it on ideological grounds. And those grounds must surely involve the “progressive” idea that humans are infinitely malleable in behavior. Unfortunately, as the Communist experiment revealed, that’s not true.

21 thoughts on “Evolutionary psychology for the tyro

  1. “tyro”

    [ looks up “tyro” ]

    well I’ll be…

    [ as if talking out loud]:

    You think you know a language, and then….

    1. Could it be that “tyro” is short for a certain large, bipedal dinosaur? I had one once, an air-filled, rubber version, but it kept deflating through a slow leak. So hard to get medical repair for dinosaurs these days, particularly when they are extinct.

  2. I really appreciate this post because I think evopsych has gotten a bad rap due to people like Jordan Peterson and the “IDW” types. They’re the ones who state their own just-so stories as if they’re facts, to further arguments for which they often have no actual data. Posts like this are a real public service because people need to see that there’s a huge difference between the field of evopsych on the one hand, and the people who fallaciously use the idea of it for their own ideological purposes on the other.

    1. I think the reason why evopsych has a bad reputation in academia is that evopsych challenges progressive values without brackets, even if you don’t look at right-wing evolutionary biologists such as Jordan Peterson (they represent almost The whole outside world’s perception of evolutionary biology), but even “centrists” like Steven Pinker have been rightly pointed out that their theories are “no different with racism”, such as certain races have lower or higher IQs, Because biological facts are so anti-progressive that for biologists on the left (over 95%) shutting up is the best way to preserve their value system, those on the left who insist on politics and biology are like The same as giving up arms against leftist anti-scientism and rightist scientism, it can only be balanced on one side in the end.

  3. My take on psychology and, by extension, evolutionary psychology are relatively new disciplines and deal with highly complex subjects. Consequently, it will take time for these disciplines to reach a firm base.

  4. The social sciences/cultural studies/marxists’ elevation of Nurture over Nature is based on flawed reasoning; it assumes that there was a specific date or point in time when
    the human species was definitively separated from its ape ancestors. This is of course anti-evolutionary at its core. It’s as if primitive humans erected a physical wall and said: here we are, we are humans and everyone before us behind that wall was not. Why doesn’t someone ask these neo-Neanderthals precisely what year this wall went up?

  5. For what it’s worth there’s a lot of conservatives that don’t like evo psych either (and not just because of the “evolutionary” component), mainly because of their belief in “free will”.

  6. Thank you for sharing this important update in this field. I expect, though, that this evidence will have minimal effect on Evo Psych detractors since evidence was not what inspired their thinking.

    1. 100% agree. This shows that (to my way of thinking), these people are crypto-creationists. After all, if you don’t accept an evolutionary explanation for our psyches/minds/behavior, what other explanation is left? The parallel with deniers of evolutionary biology seems straightforward.

    2. Hi Mark:

      PS: On your flickr page, “Tolkien” is misspelled. You may want to correct that! Love your photos.

  7. Hmmm – I have looked up the ‘studies’ that test these predictions. Much of the data comes from surveys and questionnaires (290 students at a college to ‘prove’ asymmetrical face bias, for example).
    The data, from public record, showing the rate of fathers killing their offspring, was contrary to Evo Pysch. So they looked deeper and redefined a few things, and saw that it was Step-fathers (non-kin related) that killed at a higher rate than genetically related fathers (who came in at 7%). That’s all good, except the paper dismisses, out of hand, the other possible factors that could account for this – and just settles on saying that Evo Psych explains it. (They also did not attempt to explain the 7% of kin-related murder…it’s lower, so let’s ignore it).

    Fundamentally, EP (Evo Psych) needs to show the link back to the ancestral brain’s evolution of cognitive programs to survive. Showing that some college students prefer symmetrical faces does NOT get us there.

    I agree that the brain evolved programs as adaptations for survival. It is up to EP to prove this. The problem is that ‘behaviours do not leave fossils’. And EP studies our current behaviour as an outcome of ancestral evolved survival behaviour. I understand it is a difficult field when there is almost no access to the ancestral brain, customs, social structures etc. But that is their problem, not mine.

    I sound harsh, but I am sympathetic to the cause. But it relies heavily on using current psychology tests to gather data, and THAT does give me pause.
    Most people are afraid of spiders/snakes (says the data). This is evidence of a Universal Human Behaviour says EP (one of EP’s tenets). The data is from asking people via survey. And the fact that people do not list new dangers (such as guns) shows that we fear the primal stuff from our ancestral roots. Done. Except put me in a room with a deadly spider and a guy with a gun, and then ask me what I fear! The data gathering is flawed. And the inference cannot be falsified.

    Pinker says that Music cannot be readily explained by EP. So do we just say it WILL be one day? Or do we make up stories, as the do, that maybe music made one a potentially more attractive mate…yeah, maybe – hence the ‘just so story’ criticism.
    It IS better now. But under a Lakatosian framework (rather than Popper), it is not a science so much as a Research Program. EP proponents say this, not me!

    I’m just typing this in one brain dump – probably disjointed. Apologies.

    1. None of the seven studies linked to show “prediction not explanation” were preregistered and therefore don’t provide clear evidence that these are purely theory-driven predictions. Not to cast aspersions on the authors (I’ve collaborated with several of them and contributed to this disgust literature) but the scientific culture around 2010 when these papers came out was quite different.

  8. Another criticism is that the author uses the term evolution to be synonymous with natural selection. But based on the work of many people (Stoltzfus, Nei, Koonin) there are other mechanisms of evolution, with natural selection not even being the primary factor. It makes for a frustrating read.

  9. It looks like the author’s misconception #6 does address this to a point, so kudos for that. Overall it’s interesting and worth reading.

  10. I’m leaving this comment by Boris Starosta, who for some reason couldn’t get his comment through at all:

    Some years ago, I observed (granted: ex post facto) a behavior that could only be explained through evolutionary psychology. I had taken my little boy, 3 years old, to the Baltimore Science Museum. At this time he had become a fan of dinosours (as depicted in the usual children’s books), and so we were looking forward to the very nice dinosaur exhibit there. The primary exhibit is a very large model/sculpture of a raptor, some thirty feet tall, taking down a herbivore, together with sound effects introduced into the vicinity (stamping feet and growling noises). Except that the model was perfectly static, it was quite a realistic scene. In the museum one would come upon it rounding a corner into this large space – a little bit of a surprise. I was telling my boy what we were about to see, and how cool it is.

    Thus prepared, we rounded the corner and walked about ten feet into this space. Then my boy heard the sounds and looked up and FROZE. I sensed his sudden fear, panic even, and talked to him, giving him assurance that it was only a model. He remained perfectly still, glancing at me with a look that said, “Shut up Papa! It will hear us, and you will get us eaten!” Staying as still as he could, never taking his eyes off the model, my boy very, very slowly backed away. My talk would not calm him… instead it distressed him even more, based on the looks I was given. Finally I shut up and went back around the corner with him. Of course, we did finally get him to realize that the display was not a danger to him, but it was not until a subsequent visit a year or two later that he felt comfortable in there.

    What was so striking, was that without any prior knowledge about the habits or capabilities of predators, he knew *instinctively* not to make any sudden movement nor noise. Further, his looks at me tried to communicate the seriousness of the matter! How would he have known that predators react first to movement in their field of view? It seemed clear to me that this psychological reaction was encoded into his DNA.

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