SCIENCE JOURNAL By SHARON BEGLEY
Evolutionary Psych May Not Help Explain Our Behavior After All
Like almost everyone else, David J. Buller says he was "completely captivated" by evolutionary psychology, and no wonder. This field claims to explain human behaviors that seem so widespread we must be wired for them: women preferring high-status men, and men falling for nubile babes; stepfathers abusing stepchildren. Even the more troubling claims, such as one saying rape gave our male ancestors a reproductive edge, have caught on, as laypeople and scientists alike say, yeah, that makes sense.
In a nutshell, evo psych argues that Pleistocene humans who engaged in certain behaviors left more descendants than did contemporaries who did not engage in those behaviors. As a result, we, their descendants, are wired for the behaviors.
But as Prof. Buller, a professor of philosophy at Northern Illinois University, dug deeper, he concluded that the claims of evo psych are "wrong in almost every detail" because the data underlying them are deeply flawed. His book "Adapting Minds," from MIT Press, is the most persuasive critique of evo psych I have encountered.
Take the stepfather claim. The evolutionary reasoning is this: A Stone Age man who focused his care and support on his biological children, rather than kids his mate had from an earlier liaison, would do better by evolution's scorecard (how many descendants he left) than a man who cared for his stepchildren. With this mindset, a stepfather is far more likely to abuse his stepchildren. One textbook asserts that kids living with a parent and a stepparent are some 40 times as likely to be abused as those living with biological parents.
But that's not what the data say, Prof. Buller finds. First, reports that a child living in a family with a stepfather was abused rarely say who the abuser was. Some children are abused by their biological mother, so blaming all stepchild abuse on the stepfather distorts reality. Also, a child's bruises or broken bones are more likely to be called abuse when a stepfather is in the home, and more likely to be called accidental when a biological father is, so data showing a higher incidence of abuse in homes with a stepfather are again biased. "There is no substantial difference between the rates of severe violence committed by genetic parents and by stepparents," Prof. Buller concludes.
On a lighter note, evolutionary psychology claims that men prefer fertile, nubile young women because men wired for this preference came out ahead in the contest for survival of the fittest. The key study here asked 10,047 people in 33 countries what age mate they would prefer. The men's answer: a 25-year-old.
But the men were, on average, in their late 20s. One of the most robust findings about human behavior is that people prefer a mate who matches them in education, class and religious background, ethnicity -- and age. The rule that "likes attract" is enough to explain why young men prefer young women. Besides, if you scrutinize the data, you find that 50-ish men prefer 40-something women, not 25-year-olds, undermining a core claim of evo psych.
The argument that Stone Age women preferred good providers, and that today's women are therefore wired to see a big bankroll as the ultimate aphrodisiac, is also shaky. Among some hunter-gatherers today, young mothers receive more food from their mothers than from their husbands. That makes even the theoretical basis for the claim -- that women who sought good providers had an evolutionary edge -- problematic.
The empirical basis is no better. On average, 25-year-old women say they prefer 28-year-old men, even though 50-year-old men have much more of the high status and resources that evo psych says they are wired to lust after. Again, likes attract more than "good providers" do.
In defense of the "good provider" theory, evolutionary psychologists cite studies of female college students asked to choose their ideal mate. Shown photos of young men -- one in the uniform of a fast-food worker, one looking like a middle manager, the third like a CEO -- they indeed choose one of the latter two. But just as people prefer to marry someone near them in age, they prefer to marry someone like them socioeconomically. The fact that female college students, usually middle- or upper-class, prefer medium- or high-status men could simply reflect their preference for a man who looks as though he comes from the same socioeconomic background, Prof. Buller points out. Also, earning capacity is a sign of other traits, such as education level and socioeconomic background. So although it seems that the women are being asked how important their mate's income is, they are likely using income as a sign of the other things they care about.
Evolutionary psychology has a more fundamental problem than the shakiness of its data and the fact that the data can be interpreted in more than one way. Why, if child abuse by stepfathers is such a great evolutionary strategy, do many more stepdads love and care for their stepchildren than abuse them? And why, if rape is "such an advantageous reproductive strategy, [is it that] there are so many more men who do not rape than who do," asks primatologist Frans de Waal of Emory University, Atlanta.
After "Adapting Minds," it is impossible to ever again think that human behavior is the Stone Age artifact that evolutionary psychology claims.