Field of Science

Evolutionary Psychology, Proximate Causation, & Ultimate Causation

Evolutionary psychology has always been somewhat controversial in the media for reasons that generally confuse me (Wikipedia has a nice rundown of the usual complaints). For instance, the good folks at Slate are particularly hostile (here, here and here), which is odd because they are also generally hostile towards Creationism (here, here and here). 

Given the overwhelming evidence that nearly every aspect of the human mind and behavior is at least partly heritable (and so at least partially determined by our genes), the only way to deny the claim that our minds are at least partially a product of evolution is to deny that evolution affects our genes – that is, deny the basic tenants of evolutionary theory. (I suppose you could try to deny the evidence of genetic influence on mind and behavior, but that would require turning a blind eye to such a wealth of data as to make Global Warming Denialism seem like a warm-up activity).

What's the matter with Evolutionary Psychology?

What is there to object to, anyway? Some of the problem seems definitional. Super-Science-Blogger Greg Laden acknowledges that applying evolutionary theory to the study of the human mind is a good idea, but that "evolutionary psychology" refers only to a very specific theory from Cosmides and Tooby, one with which he takes issue. And in general, a lot of the "critiques" I see in the media seem to involve equating the entire field with some specific hypothesis or set of hypotheses, particularly the more exotic ones. 

For instance, some years back Slate ran an article about "Evolutionary Psychology's Anti-Semite", a discussion of Kevin MacDonald, who has an idiosyncratic notion of Judaism as a "group evolution strategy" to maximize, through eugenics, intelligence (the article goes into some detail). It's a pretty nutty idea, gets basic historical facts wrong, and more importantly gets the science wrong. The article tries pretty hard to paint him as a mainstream Evolutionary Psychologist nonetheless. Interviewees aren't that helpful (they mostly dismiss the work as contradicting basic fundamentals of evolutionary theory), but the article author pulls up other evidence, like the fact that MacDonald acknowledged some mainstream researchers in one of his books. (For the record, I acknowledge Benicio del Toro as an inspiration, so you know he fully agrees with everything in this blog post. Oh, and Jenna-Louise Coleman, too.)

This spring, New York Times columnist John Tierney asserted that men must be innately more competitive than women since they monopolize the trophies in -- hold onto your vowels -- world Scrabble competitions. To bolster his case, Tierney turned to evolutionary psychology. In the distant past, he argued, a no-holds-barred desire to win would have been an adaptive advantage for many men, allowing them to get more girls, have more kids, and pass on their competitive genes to today's word-memorizing, vowel-hoarding Scrabble champs.
I will agree that this argument involves a bit of a stretch and is awfully hard to falsify (as the article goes on to point out). And sure, some claims made even by serious evolutionary psychologists are hard to falsify with current technology ... but then so is String Theory. And we do have many methods for testing evolutionary theory in general, and roughly the same ones work whether you are studying the mind and behavior or purely physical attributes of organisms. So, again, if you want to deny that claims about evolutionary psychology are testable, then you end up having to make roughly the same claim about evolutionary theory in general. 

Just common sense

It turns out that when you look at the biology, a good waist-hips ratio for a healthy woman is (roughly) .7, whereas the ideal for men is closer to .9. Now imagine we have a species of early hominids (Group A) that is genetically predispositioned such as that heterosexual men prefer women with a waist-hips ratio of .7 and heterosexual women prefer men with a waist-hips ratio of .9. Now let's say we have another species of early hominids (Group B) where the preferences are reversed, preferring men with ratios of .7 and women with ratios of .9. Since individuals of Group A prefer to mate with healthier partners than Group B does, which one do you think is going to have more surviving children? 

Now compare to Group C, where there is no innate component to interest in waist-hips ratios; beauty has to be learned. Group C is still at a disadvantage to Group A, since some of the people in it will learn to prefer the wrong proportions and preferentially mate with less healthy individuals. In short, all else equal, you would expect evolution to lead to hominids that prefer to mate with hominids that have close-to-ideal proportions.

(If you don't like waist-hips ratios, consider that humans prefer individuals without deformities and gaping sores and boils, and then play the same game.)

Here is another example. Suppose that in Group A, individuals find babies cute, which leads them to want to protect and nourish the infants. In Group B, individuals find babies repulsive, and many actually have an irrational fear of babies (that is, treating babies something like how we treat spiders, snakes & slugs). Which one do you think has more children that survive to adulthood? Once again, it's better to have a love of cuteness hardwired in rather than something you have to learn from society, since all it takes is for a society to get a few crazy ideas about what cute looks like ("they look better decapitated!") and then the whole civilization is wiped out. 

(If you think that babies just *are* objectively cute and that there's no psychology involved, consider this: Which do you find cuter, a human baby or a skunk baby? Which do you think a mother skunk finds cuter?)

These are the kinds of issues that mainstream evolutionary psychology trucks in. And the theory does produce new predictions. For instance, you'd expect that in species where a .7 waist-hips ratio is not ideal for females (that is, pretty much any species other than our own), it wouldn't be favored (and it isn't). And the field is generally fairly sensible, which is not to say that all the predictions are right or that evolutionary theory doesn't grow and improve over time (I understand from a recent conversation that there is now some argument about whether an instinct for third-party punishment is required for sustainable altruism, which is something I had thought was a settled matter). 


Vic said...

There is a lot of shady studies within the field of evolutionary psychology, but name one scientific field that hasn't? the problem with evolutionary psychology mostly stem from 3rd wave feminists whose whole ideology and theoretical framework is based on the notions that the minds of men and women are the same and that differences in behaviour are social constructs. Any scientific field that challenges this notion will be scrutinized by these people.

GamesWithWords said...

I agree. We mostly think of political interference in science coming from conservatives (evolution, global warming, etc.), but evolutionary psych is definitely one of the places where the facts butt up against cherished *liberal* beliefs.