Evolutionary psychology for the tyro

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

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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:

Disgust

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.