In defense of evolutionary psychology, part 1: introduction and the pleistocene

Within the skeptic/atheist/rationalist internets, there seems to be a rather striking divide between folks who take for granted the basic ideas of evolutionary psychology and drop off-hand references to Steven Pinker and Cosmides and Tooby, and folks who disagree and drop off-hand references to the fact that evolutionary psychology is evil. I’m very much in the former camp–I mentioned being a big fan of Steven Pinker in my introductory post.

The two camps don’t seem to talk to each other much. Maybe that’s because this is a hard issue to even talk about, in part because of a lack of agreement on what “evolutionary psychology” even means. But if there’s any authoritative source for what evolutionary psychology is, it’s probably the anthology The Adapted Mind, edited by Jerome Barkow, Leda Cosmides, and John Tooby. And here’s how they define their project in the introduction:

The central premise of The Adapted Mind is that there is a universal human nature, but that this universality exists primarily at the level of evolved psychological mechanisms, not of expressed cultural behaviors. On this view, cultural variability is not a challenge to claims of universality, but rather data that can give one insight into the structure of the psychological mechanisms that helped generate it. A second premise is that these evolved psychological mechanisms are adaptations, constructed by natural selection over evolutionary time. A third assumption made by most of the contributors is that the evolved structure of the human mind is adapted to the way of life of Pleistocene hunter-gatherers, and not necessarily to our modem circumstances (p. 5).

I know a lot of people will object to assuming that what the editors call “psychological mechanisms” are adaptations, and I plan on dealing with that issue in a future post. But what actually sticks out at me as the weakest point in this set of three assumptions is the third assumption, about the Pleistocene. There’s a slight nod to doubts people might have about it when the editors say it’s made by “most of our contributors,” a qualification they didn’t make with the first two assumptions. Furthermore, recent studies showing an increase in the rate of human evolution (see here and here, for example) may seem to contradict this assumption.

However, if you read just a bit beyond the section I’ve quoted, I think it becomes clear that this third assumption, taken as the editors intended it, is well-motivated and compatible recent findings about the rate of human evolution since the advent of agriculture. They explain that, “it is unlikely that new complex designs—ones requiring the coordinated assembly of many novel, functionally integrated features—could evolve in so few generations,” which doesn’t rule out adapting to recent changes in subtler ways.

Similarly, they say, “If selection had constructed complex new adaptations rapidly over historical time, then populations that have been agricultural for several thousand years would differ sharply in their evolved architecture from populations that until recently practiced hunting and gathering. They do not.” Again, this doesn’t rule out subtler differences between those human populations as a result of changes in lifestyle (think ability to digest lactose).

Okay, simple issue gotten out of the way. Feel free to use this as a thread for evo psych bashing, but if you’re going to make a claim of the form “evolutionary psychology says X” or “evolutionary psychologists do Y,” tell me whose work you’re referring to. Cosmides and Tooby’s? Donald Symons’? David Buss’? Steven Pinker’s? Robert Trivers’? Geoffrey Miller’s? Whose?

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