Is Evolutionary Psychology Impossible?

I have talked about evolutionary psychology — or, more often, its critics — before on this blog. For the most part, I’ve found that most of the criticisms of it end up criticizing it for either the failings of evolution or the failings of psychology. Obviously, evolutionary psychologists can overplay and overextend their evolutionary explanations for our psychology, but this is a failing of normal psychology as well that I’ve grumbled about in the past. It’s difficult to find criticism of the field that really takes on the combination of the two.

I’m not sure that the latest criticism going around by Subrena E. Smith really counts, but it is coming from a philosopher and is a novel approach, as it is trying to argue that we could never sufficiently justify an evolutionary explanation for our psychological traits. I will talk about the implications of that more later, but it is important to note now that, despite how some people are viewing it, this would not at all mean that we don’t have traits due to evolution. All it would mean that if there were such traits, we at a minimum couldn’t know what they are. It’s entirely possible that we could find sufficient evidence to know that at least some of our traits have evolved, but have no idea which ones. It is thus an epistemic argument, not a factual.

First, I’m going to examine some of the issues with the argument, and then follow up with what it would mean for psychology and science if the argument actually worked. Note that I don’t have access to her paper, so I’m relying on the blog post cited above and perhaps a bit from this interview with her.

Smith’s main thrust is that evolutionary psychology needs to solve what she calls the “matching problem”, but that it isn’t capable of doing so:

Evolutionary psychological claims, therefore, fail unless practitioners can show that mental structures underpinning present-day behaviors are structures that evolved in prehistory for the performance of adaptive tasks that it is still their function to perform. This is the matching problem.

Well, actually, this doesn’t seem to be the case. When it comes to evolved traits, it seems to me that the most obvious cases are in fact those where we can point to a trait that would have had a specific function in prehistory, but that don’t have that function today, and yet we still have them. If a trait seems like it would have been beneficial in the past but is actually detrimental now, it’s certainly not the case that it is being selected for now based on its having a clear use. This is only going to be more obvious for psychological traits, because as Smith notes our psychological mechanisms are more flexible than our physical ones, but what this means is that if a psychological trait is problematic now something must be maintaining it or, rather, keeping it from changing as part of normal psychological flexibility and plasticity. The two main candidates for that are that it is physically/genetically spawned, or that it is societally spawned. The former is evolutionary psychology, and the latter is an explanation that critics, rightly, say evolutionary psychology needs to be more diligent in ruling out. But at the end of the day, unchanging, detrimental psychological traits that are mostly universal and less individual are going to be the most obvious cases of them being selected for by evolution.

An example of this would be the sweet tooth, although whether that counts as a psychological trait or a more physical one is more debatable. However, seeking out sweet foods was incredibly useful in the past and in prehistory when such things were rare, but now is maladaptive when sweet foods are easy to come by. This is actually causing physical issues with us, including early deaths, and so is something that we wouldn’t have developed in modern times with the modern environment, either by evolution or our early development. And yet, we act that way anyway, and it seems remarkably resistant to attempts to change it. This is a prime candidate for something that has evolved, and as far as I am aware there is little doubt that it is an evolved trait. And yet it no longer performs the same function, and it is precisely that difference that allows us to deduce that it is an evolved trait.

That’s a big issue here. Smith is right to note that with psychology we have to be careful to and yet would have a difficult time differentiating the evolved psychological traits from societal ones or ones that we develop from our existing environment, but the real difficulty with that will be precisely those cases where the function and behaviour are the same, meaning that the current environment is similar enough to the prehistoric one for those traits to roughly work the same way. However, where the environment is sharply different, then we will be able to note all of those traits that are acting in ways that it isn’t reasonable to expect would develop from simple interaction with the environment or that we could get from society. Yet Smith demands that we can only reasonably consider the cases where the behaviour is identical, which are the ones that are the most difficult to separate from our current environment and society. This seems to do evolutionary psychology a disservice. If she was correct that the mechanisms had to have the same function, she’d have a point, but that has never been the case for evolutionary explanations, so it seems unreasonable to insist upon it here.

Another issue comes up when we realize that Smith is relying heavily on the idea of confounds. Throughout the entire piece, she bases her claims for strong required evidence on the basis that if evolutionary psychology can’t meet them, then they can’t separate themselves from the possibility of it being developed either societally or through normal development. But while I myself use confounds against psychology on occasion, what I do is point out that a specific experiment or explanation is not as definitive as those advocating it make it seem. I’m not insisting that their explanation cannot be correct because I can come up with another explanation. Smith is demanding that they demonstrate their case to the degree that she couldn’t come up with any other even semi-reasonable explanation. Confounds don’t work that way.

This also clashes with science. Smith is demanding such a high degree of evidence that we would have to be almost certain that the evolutionary psychological explanation was the correct one. She does this without even considering whether the societal or development models can offer any reasonable explanation for the trait. But science does not work that way. Science always takes the most reasonable explanation given the alternatives. So Smith cannot say that for any trait unless evolutionary psychology can eliminate the other alternatives that we would never accept it as an explanation for a trait. As long as the explanation that is most reasonable is the evolutionary psychological one, that’s the one that we would accept. So, epistemically, she seems to indeed be holding evolutionary psychology to too high a standard.

This only gets worse when we realize that some traits would seem to be more tightly tied to evolution than others. Given how important reproduction is to evolution and how subconscious it is, it would be quite unlikely if none of that was still driven by those initial and underlying evolutionary pressures. We can also see that food preferences, like the sweet tooth, are likely to be driven by those evolutionary pressures. And while Smith gives evolutionary explanations a way out that she doesn’t grant to evolutionary psychology:

Comparative methods are not reliably informative, as there are no extant species that are closely related to Homo sapiens and the relevant behaviors are not generally highly conserved.

… arguments about the secular possibility of morality do precisely that, by noting rudimentary moral behaviour in closely related animals and arguing that thus morality likely evolved. Any psychological trait that has a rudimentary or even relatively full expression in near relative animals would be a prime candidate for a trait that evolved. So Smith needs to ignore cases where we’d have to give the advantage to the evolutionary psychological explanation to insist that it would have to eliminate all the others first.

So, it seems like her argument isn’t particularly strong. But what if it worked? What would that mean for science?

Remember, nothing in Smith’s argument says that evolutionary psychology is factually false. Given what I’ve said above and adding in what we know about the brain — in particular, that we actually have older and newer areas of the brain that evolved under different conditions — it seems pretty likely that at least some of our psychological traits are the result of evolution. So the consequences of her argument are, as noted above, that if there are such traits, psychology — and by extension science — could never discover them. Thus, there are true propositions about the world that science could never discover. This … is not something that scientists should want to accept, especially following on from evolution and the difficulties of justifying those sorts of explanations. Many scientists have been struggling for ages to assure us that science can know anything that is true and that we can know all of our traits have evolved. This is in fact a driving force behind the insistence that consciousness is all in the brain and has evolved along with it. To argue that mental traits cannot be shown to have evolved in principle undercuts all of that. Ultimately, this argument undercuts all arguments from scientism or against the theological notion of the soul.

So it’s kinda surprising that P.Z. Myers likes it so much. Then again, he’s known for supporting short-sighted views if they let him mock a view or group that he really wants to mock.

Smith’s argument isn’t that strong. It especially isn’t all that strong given the strong implication that it has, of potential facts about the world forever cut off from science. If it wasn’t attacking something that many people already dislike, I suspect that more people would be critical of it. As it stands, I don’t think it can establish that evolutionary psychology is, in principle, impossible.