In the January 2009 special edition of Scientific American there is a scathing report on evolutionary psychology (EP). The report raises concerns about the way evolutionary psychology is being carried out and the truth claims it is making. The article was written by Dr. David Butler, a professor of philosophy at Northern Illinois University.

I should point out that Butler believes that our mental capacities evolved, however, he is skeptical of the truth claims being made in EP. He says that many of the “grand and encompassing” claims lack rigorous empirical evidence. The claims may be correct, but EP does not have sufficient evidence to back them up.

Here are the four concerns he raises.

1. We cannot know our ancestors’ psychological traits.
EP claims to understand the adaptive problems that our Pleistocene ancestors faced. An understanding of these adaptive problems is essential to understanding how the human mind evolved. Yet, Butler points out, the paleontological record provides few clues about the challenges our early ancestors faced. It also says very little about their social interactions which would have played a major role in shaping how the human mind evolved to cope with social challenges. Without knowing the social and physical challenges they faced, we know very little about their psychology. If we do not know the psychological starting point, we cannot know how evolution shaped their minds.

2. Evolutionary psychologists are limited in their use of comparative methods.
To better understand how and why our adaptive mental traits evolved, one must do comparative research (i.e., compare the development of similar traits in a nearby species). However, Butler points out that our nearest living ancestors do not possess many of the same psychological traits that make us uniquely human (e.g., verbal language). Thus we lack crucial evidence needed to uncover our psychological evolutionary history.

3. EP is stuck in the Pleistocene era.
Butler says that EP relies too heavily on the Pleistocene era when describing the evolution of human psychology. He quotes the oft used statement “our modern skulls house a stone age mind” as evidence of this problem. He says “The idea that we are stuck with a Pleistocene-adapted psychology greatly underestimates the rate at which natural selection and sexual selection can drive evolutionary change.” For instance, the more recent agricultural and industrial revolutions presented challenges that greatly shaped human psychology. We are not locked in a stone-age mindset.

4. Some EP truth claims rest on shaky empirical evidence, and always will.
EP claims that it has uncovered human psychological adoptions. Much of the data supporting these claims were gathered with paper and pencil surveys (questionnaires). Forced choice questionnaires do not provide sufficient evidence to substantiate claims about how psychology adapted to social and physical environmental challenges. Thus, “the evidence needed to substantiate accounts of adaption…is scarce. And this isn’t the kind of evidence that is likely to materialize; such evidence is lost to us, probably forever.”

I have found that the same sort of arguments may be used against common descent. Specifically, as far as common descent is concerned, we cannot know exactly what took place back when organisms were supposedly evolving from one species into another because we were not there. Our evidence for common descent is largely driven by the historical fossil record. Try as we might to paint a picture of what happened, we cannot be certain. Moreover, decisive evidence that evolution across life forms will always be lacking because of the long period of time required to observe these supposed processes at work.

One final thought. Butler is not suggesting that EP close up shop. He is just pointing out its limitations and cautioning it from making unsupportable truth claims. In the same way I am not suggesting that common descent scientists stop their work. I am just pointing out its limitations and cautioning it from making truth claims that lack definitive evidence.

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