Evolutionary psychologists have a knack for simple, memorable descriptions of their view of the human mind. For example, “Our modern skulls house a stone age mind.”

That hits a lot of the right buttons, doesn’t it? We all know people who, we suspect, think that way. Seldom do we ask, how do we know it is true? Meanwhile, thousands of popular science articles over the years have claimed to tell us why we vote or shop a certain way, tip at restaurants, or fear snakes.

Now, one bold philosopher has asked. And the fallout from Subrena E. Smith’s critique, “Is Evolutionary Psychology Possible?”, may be falling for quite some time.

Smith (above right), an assistant professor of philosophy at the University of New Hampshire, asks what, specifically, do evolutionary psychologists claim about the human mind? How would we know if their claims are true?

Evolutionary psychologists believe that we inherited Stone Age minds, largely unchanged, from remote ancestors in the form of modules that govern our behavior. These modules performed such highly specialized tasks as “predator avoidance, mate selection, and cheater detection.” (P. 40) The way we behave today, according to evolutionary psychologists, is governed by these modules, though we don’t realize it. As one research group claims, “Behavior in the present is generated by information-processing modules that exist because they solved adaptive problems in the past.”

Neuroscience has not identified any such modules. Even if they exist, how do we know that they are identical to those of humans who lived 50,000 years ago? Brains don’t fossilize. Smith calls this the “matching problem”: “Unless the challenge can be overcome, evolutionary psychological explanations fail. Put more strongly, if the matching problem cannot be solved, evolutionary psychology is impossible.” (P. 42)

To try to overcome this problem, evolutionary psychologists default to one of two strategies: They identify a typical modern behavior and then try to determine how that behavior might have helped remote ancestors survive. Or, alternatively, they identify challenges our ancestors faced and try to determine how facing those challenges shaped contemporary human psychology.

But now another problem arises. Smith points out a critical distinction between contemporary animal psychology and evolutionary psychology for humans (p. 43). Chimpanzees today live pretty much as they did millions of years ago. It is reasonable to think that their present behavior is inherited from their past behavior. Human life, by contrast, has vastly changed since the Stone Age. So we don’t have a basis for making the same assumptions.

It feels odd, somehow, that strongly committed evolutionists are so reluctant to accept the idea of actual, permanent change.

Smith goes on to note that evolutionary psychologists offer “subpersonal” explanations for behavior; that is, what you think you are doing can be ignored because in reality you are just fulfilling your evolutionary programming. But explanations at the subpersonal level break down in this case. By definition, we don’t know the details of what happened in the prehistoric past: “Accordingly, it is illegitimate to infer from a behavior that contributes to reproductive success now, that it contributed to reproductive success in the ancestral past… (P. 45)

She offers an illustration of the problem: A 2009 study attempted to show that men care more about infidelity than women because of the biological cost: “Ancestral men … were susceptible to an additional and profound cost if they failed to detect a partner’s infidelity: cuckoldry — the unwitting investment of resources into genetically unrelated offspring.”

The thesis depends on the assumption that men in prehistoric human communities even knew which of the children who appeared every so often were their own — and we know nothing of how such momentous realizations came about. No matter, the researchers tested their hypothesis by asking 163 male and female college students to predict the future fidelity of their current partner. They found suspicion more common among the men than the women. They concluded that “men’s infidelity detection system should be designed to overestimate the likelihood of their partner’s infidelity.” (Goetz and Causey, 2009, p. 262)

Smith offers a number of reasons for dismissing such conclusions as unjustified:

Comparative methods are not available for assessing the claim that male skepticism about female fidelity was selected for. Furthermore, it is not obvious that this attitude leads to fitness-enhancing behavior in the present, and that the fitness of human males would be diminished in its absence. Also, it has not been established that prehistoric mating involved exclusive pair-bonding rather than, for example, promiscuity within the group. There is no good evidence that males’ skepticism about their female partners’ fidelity is under genetic control, and there is no dedicated neurological mechanism known to mediate it (the module controlling the attitude is entirely hypothetical). Finally, that this is not an automatic response is evidenced by successful polyamorous relationships. (P. 47)

One might add that, when we look for sources of present-day behavior in the remote past, we neglect contemporary drivers that we can study more rigorously. For example, the costs to college men of women’s infidelity today may not center on children at all. Social and economic issues unknown to the Stone Age may drive many male students’ concerns.

A brilliant takedown and a brave one, on the part of Smith — and long overdue. These problems with evolutionary psychology have been staring us in the face for decades. But questioning any enterprise that gets itself associated with Darwinian evolution, no matter how flawed the reasoning or how paltry the evidence, comes at a cost few want to risk: being seen as “anti-science” or “anti-evolution.”

Things may be changing, as serious issues force decisions on us. The Evolution Institute seemed quite happy to give Smith an opportunity to explain her thesis and accommodate respectful replies. She was interviewed, again respectfully, by Ryan F. Mandelbaum at Gizmodo.

Many of us were surprised to learn from Mandelbaum that “We at Gizmodo have long rolled our eyes at the often-nonsensical conclusions that some people come to when employing evolutionary psychology theory …” If so, they are outliers. Many popular science publications have grabbed at highly implausible evo psych theses over the years, with never a qualm about how they can legitimately form a part of science.

Even Darwinian biologists are chiming in. Jerry Coyne defends evo psych from Smith but concedes that “a lot of us don’t accept “Evolutionary Psychology”, at least as Smith construes it in her paper.” From a less sympathetic source, P. Z. Myers: “The defenders of evolutionary psychology just carry on, doing more and more garbage science built on ignorance of evolutionary biology, publishing the same ol’ crap to pollute the scientific literature.”

Either way, rejecting evolutionary psychology as a serious enterprise amounts to a collective realization that one cannot both claim to represent “science” and, at the same time, refuse to be bound by any recognizable standards of science. Time will tell if this mood lasts.

Paper: Subrena E. Smith, Is Evolutionary Psychology Possible? Biological Theory 15 (1): 39-49. 2020 (subscription required)

Further reading: Meat has no opinions. Why you can’t actually deny free will. (Michael Egnor)