The human brain, just like every aspect of every organism on the planet, is the product of evolution. If you accept that evolution is true, you can’t avoid that conclusion. That’s why I often get confused when I hear reasonable people being broadly dismissive of evolutionary psychology (EP).

EP is simply an approach to psychology that explicitly acknowledges evolution as the designer of brains. This approach may sound non-controversial in principle, at least among those who accept evolution. Nevertheless, many non-creationist critics find plenty of reasons to object to EP, or at least to what they consider EP to be. For examples of some such criticisms see Ed Hagen’s Evolutionary Psychology FAQ.

Because many critics of EP would say they accept evolutionary theory more generally, I assume that in criticizing EP they don’t mean to imply that the brain wasn’t designed by evolution. I think they often instead intend to critique some specific EP hypothesis or result, or some particular approach to doing EP that they are treating as though it represented the entire EP enterprise. For example, they may object to an EP prediction of a biologically-based difference between men and women, or to an EP finding that suggests that human nature is adapted for physical aggression under certain conditions. They may dislike an EP approach that expects the brain to be composed of an implausibly-large-seeming number of mental modules, or that is based on overly-speculative-seeming assumptions about what the environments of our evolutionary ancestors were like. The problem is, although these critiques are often triggered by a specific perceived implication of EP that is regarded with incredulity or disapproval, critics don’t always restrict themselves to challenging only this specific implication. Instead they regard their objection as a reason to attack the entire field of EP.

In any scientific field, critiques of particular hypotheses or approaches are essential for moving knowledge forward, and so such critiques are as welcome in EP as in any other field. However in order to be productive, such critiques do need to focus on specific targets (such as on a hypothesis that is seen as being less predictive than an alternative hypothesis). Any critique that broadly dismisses the whole EP enterprise—that is, the whole notion that we can use evolutionary theory to understand the brain—is taking a position that is, intellectually and scientifically, very difficult to defend. What is the explicit alternative to ‘evolutionary’ psychology? Creationist psychology? Non-evolutionary psychology? Anti-evolutionary psychology?[1] And if some such ‘un-EP’ approach is the correct way to do psychology, what are the rules of this approach? Would the cardinal rule be that it’s fine to study the brain (and brain products, like the mind, behaviour, and culture), as long as we never acknowledge or identify the process that designed the brain?

There is more than one way to do EP, and advocates of different EP approaches frequently argue, often productively, about the merits of their preferred approach. There are also many competing EP hypotheses about how evolution built various aspects of the brain and human nature. These debates may center on issues such as “is trait X an adaptation, a by-product of an adaptation, or just a random effect of the evolutionary process?” Or, “if trait X is an adaptation, then what adaptive problem did it evolve to solve?” Such debates are necessary for generating knowledge and moving the field forward. But conflict that targets the field of EP as a whole—that attacks the whole notion of using evolutionary theory to illuminate psychology—is not just unproductive but also intellectually reckless and irresponsible. If a critic is seriously proposing that knowledge of evolution cannot enhance our understanding of the brain, then he or she needs to be clear about why this proposition would be true. Is the critic proposing that human neural tissue, unlike every other kind of organismal tissue, is immune to the process of natural selection? If so, this is a radical scientific notion. It would be one of the greatest discoveries ever and the most important advance in biology at least since the discovery of DNA. It’s an extraordinary claim that would require extraordinary evidence before it could be taken seriously.

Of course, I doubt that many critics of the general EP enterprise would really claim to have ‘discovered’ that the human brain has been excluded from the laws of evolution. Nevertheless, such critics should be aware that in attacking this general enterprise, they do seem to be positioning themselves in defense of this indefensible claim.

My own view on these matters jibes with that expressed by other evolutionary psychologists: ‘evolutionary psychology’ is in fact a redundancy, in that all psychology is evolutionary psychology. I mean this in the same sense that all anatomy is ‘evolutionary anatomy.’ Any approach to human anatomy would be impotent unless it assumed that organs have specific functions that promote (or that in the evolutionary past promoted) the organism’s survival and reproduction. Anatomists understand, for example, that the heart functions to pump blood and the intestines function to extract nutrients from food. And when it comes to accounting for function scientifically, there is only one game in town: natural selection. No other known process can build a functional organismal trait (that is, an adaptation). So regardless of whether you accept evolution, you can’t do anatomy without studying organs that are evolutionary adaptations, and you can’t understand these organs without at least implicitly invoking evolutionary principles like functional specialisation for survival and reproduction. Since human neural tissue has been sculpted by the same evolutionary processes as all other tissue, these same principles apply to the study of psychology. If we’re doing psychology, therefore, then we’re also doing evolutionary psychology: we’re trying to understand evolved adaptations—and their mental, behavioral, and cultural products and by-products—and our ability to do so is enhanced through the invocation of evolutionary principles.

[1] Here I’m paraphrasing some online comments made recently by psychologist Michael Mills of Loyola Marymount University, USA.