Psyching Out Evolutionary Psychology

Interview by JR Minkel

Philosopher of science David Buller has a bone to pick with evolutionary psychology, the idea that some important human behaviors are best explained as evolutionary adaptations to the struggles we faced tens to hundreds of thousands of years ago as hunter-gatherers. In his new book, Adapting Minds, the Northern Illinois University professor considers--and finds lacking--the evidence for some of the most publicized conclusions of evolutionary psychologists: Men innately prefer to mate with young, nubile women, while women have evolved to seek high status men; men are wired to have a strong jealous reaction to sexual infidelity, while women react to emotional infidelity; and parents are more likely to abuse stepchildren than their genetically related children.

Buller doesn't reject evolutionary studies of the mind per se. Rather, he contends that "Evolutionary Psychology," a set of assumptions about the nature and evolution of the human mind, has largely crowded out the possibility of a more pluralistic "evolutionary psychology." Writer JR Minkel recently spoke to Buller to get a bead on his argument. An abridged and edited transcript of their conversation follows.

JR Minkel: What was your initial reaction to the conclusions of Evolutionary Psychology, and when did you first start having doubts about them?

David Buller: When I first started reading it, it just all seemed intuitively right to me. But as I followed the citation trail and actually started looking at the primary studies that were cited in support of those conclusions--and thinking seriously about the methods that had been employed in the studies, the presuppositions behind them, and whether there were alternative evolutionary hypotheses for the things studied that were not in fact being ruled out by the experiments--I began to find that it wasn't all that convincing.

JRM: Why did you feel the need to write a book, given the criticisms the field has already received?

DB: I didn't feel that there was a broader framework in which the whole paradigm was viewed as fundamentally problematic. I saw the writing of this book just as a desire to synthesize a variety of the problems I saw with the paradigm, some of which had been pointed out by other people already.

What I thought needed to be brought out for a more general readership were some of the methodological problems involved in these very highly publicized discoveries that evolutionary psychologists claim to have made; things that get covered in the New York Times on pretty much a weekly basis. I wanted to show people that there are grounds for skepticism.

JRM: Why do you say the evolutionary psychology paradigm is problematic?

DB: There are three foundational claims that it makes. One is that the nature of [evolutionary] adaptation is going to create massive modularity in the mind--separate mental organs functionally specialized for separate tasks. Second, that those modules continue to be adapted to a hunter-gatherer way of life. And third, that these modules are universal and define a universal human nature. I think that all three of those claims are deeply problematic.

If anything the evidence indicates that the great cognitive achievement in human evolution was cortical plasticity, which allows for rapidly adaptive changes to the environment, both across evolutionary time and [across] individual lifetimes. Because of that, we're not quite the Pleistocene relics that Evolutionary Psychology claims. [Regarding universality,] all of the evidence indicates that [behavioral] polymorphisms are much more widespread in all sexually reproducing populations than the idea of a universal human nature would require. So I think the theoretical foundations from which a lot of predictions get made, about what our mate preferences are going to be, or what the psychology of parental care is, are problematic because the theoretical foundation is mistaken.

JRM:In the book you also point out the difficulty of reconstructing the ancient environment that evolutionary psychologists argue has shaped the human mind.

DB: Even by their own account, human psychology evolved for the most part to deal with human psychology, to put it crudely. You can't be specific about what the adaptive demands were on human psychology without knowing something about the way that humans minds were working then, and that's something we just don't know.

JRM: Which conclusion of Evolutionary Psychology do you think has most captivated the public?

DB: Probably the issue of mate preferences, this whole idea that males have this ineluctable preference to mate with nubile females, and that females have this ineluctable preference to mate with high status males. As soon as you see those claims you can immediately think of a number of confirming examples of it. The evolutionary psychologist David Buss is very fond of pointing to Hollywood stars and saying, "See, these people illustrate the truth of our claims." But when you look at the broader range of evidence that's out there I think it doesn't really support these claims.

As I point out in one section about male preferences, there's a tendency to focus on older males who reenter the mating market after divorce, and evolutionary psychologists take this to be pretty firmly clinching evidence in favor of their hypothesis. But that neglects over half of older males who remain mated to older women. Look at Paul Newman--a very high status male, but [he] has remained monogamously married to a woman his own age. Those are choices that males make, and you can't just exclude one half of the population from the data against which you're going to test your hypothesis.

My hypothesis is that in most men, the adaptation is a preference for similarly-aged mates--adjusted for sex differences in the ages at which reproductive maturity are reached--rather than an adaptation to prefer nubility. This preference tends to contribute to the selection of a nubile mate because most marrying men are young. The difference between my hypothesis and Evolutionary Psychology's claim can't be seen when looking at the mate choices of young males. It's only when we look at older males that the two hypotheses differ in their predictions. As I argue at some length in chapter five, I think the evidence on the whole favors my hypothesis.

JRM: Do you see any value in Evolutionary Psychology? You mention in the book that it has led to evolutionary hypotheses about jealousy, for example.

DB: It has led to the asking of questions that needed to be asked, so in that regard I think it's been a very positive development. Evolutionary theory has not been applied to the study of humans to quite the extent that it should have been to date. I think looking at an emotion like jealousy from an adaptationist standpoint is very positive. It stimulates lines of research that would not have occurred otherwise. But immediately then the paradigm kicks in with its big theoretical apparatus and says, "Oh, well ok, but if jealousy is an adaptation, then differences in the sexes require differences in modules in the sexes." So then you get the whole account of jealousy that's propounded in the paradigm--the idea that there's an evolved sex difference, where males are sexually jealous and females are emotionally jealous. So while I think the paradigm has been an extremely positive development on the whole, it has tended to prematurely narrow the kinds of hypotheses that are considered about human evolution.

I have not seen in the literature any alternative evolutionary accounts of jealousy. The literature that tends to be critical of that particular hypothesis refers to it as the evolutionary account of jealousy and, in rejecting the particular hypothesis of an evolved sex difference, goes on to reject an evolutionary account of jealousy. I think that's premature. I think jealousy can be an adaptation but it doesn't require that there is an evolved sex differences in the design features of the male and female minds.

I have a colleague in the psychology department, Brad Sagarin, and we have started gathering some data to explore other evolutionary hypotheses [for jealousy], like the one that I articulate in the book. [Editor's note: Called the relationship jeopardy hypothesis, it supposes that men and women have the same evolved capacity to learn to distinguish threats to the relationship from nonthreats.] We're still just gathering data. One thing that we're talking about in the research group is ways of creating jealousy in a laboratory setting. Coming up with a way of doing this that is ethical is not at all that easy. The easy way is to use the same sorts of questionnaire studies that have been used before, but to broaden the questions that you use them to address.

One piece of propaganda that people in the Evolutionary Psychology paradigm have used in support of their approach is [to assert] that throughout the history of psychology, evolutionary thinking has been almost entirely absent. They present themselves as having the courage to ask evolutionary questions about human psychology. Certainly we have evolved, like all other life on the planet, and we should be looking at human psychology from an evolutionary perspective. My disagreement with the Evolutionary Psychology paradigm is with respect to what follows from taking an evolutionary perspective on human behavior and psychology. The paradigm [supposes] that a lot of very specific doctrines immediately begin to follow once you take that perspective, and I don't think that's true. It's much more wide open.

JRM: What are other examples of proposed evolutionary explanations for human behavior that fall outside the paradigm?

DB: Some of the examples I discuss in the book are Barbara Smuts and David Gubernick's mating effort hypothesis concerning the evolution of marriage, and Kristen Hawkes's "grandmother hypothesis" for the evolution of menopause. In my opinion, these are terrific examples of work in evolutionary psychology, as opposed to Evolutionary Psychology. One significant difference between this work and the Evolutionary Psychology paradigm is that it isn't driven by an underlying "Grand Unified Theory" about the nature and evolution of the human mind. The good work to date, I think, has tended to be piecemeal, focused only on narrow aspects of human life history and decision-making.

The other major topic you address in the book is child abuse. You went so far as to collect data from the National Data Archive on Child Abuse and Neglect to examine patterns of abuse in the U.S. Why are you skeptical of the claim that parents are more likely to abuse stepchildren?

DB: It's a long and complicated argument. To oversimplify, I will say, first, we need to make sure that we're looking at the right sample. As I argued, to test evolutionary psychology's hypothesis, we need to look at physically abused children, not sexually abused children or children who were the victims of very broadly defined neglect. Second, in my study, the sample of physically abused children was 10 times the size of the sample in [a study by evolutionary psychologists Martin Daly and Margo Wilson]. Third, the differential I found in that larger U.S. study is readily accounted for by U.S. data regarding a diagnostic bias against those classified as stepparents. Fourth, I found clear evidence that much abuse in stepfamilies is at the hands of genetic parents. These things conspire to raise doubts about the "received view" of stepparental abuse.

JRM: Was your study peer-reviewed?

DB: A very brief version of it appears in an article of mine in the June issue of Trends in Cognitive Sciences. So some of it was published in a peer-reviewed journal a little after the release of my book. It wasn't rejected by peer-reviewed journals, either. I never submitted the research apart from my book.

JRM: Another recent book, The Case of the Female Orgasm, by biologist and philosopher of science Elisabeth Lloyd, examines the evidence for various adaptive explanations of female orgasms, and concludes that it has no evolutionary function. Do you think she's right?

DB: I haven't read the book yet. However, I've read her earlier work on female orgasm, I've seen her give a couple of talks on her research, and I've discussed her work with her briefly. I'm not completely convinced that Lloyd is right that female orgasm has no evolutionary function, although my mind could change once I read the whole book. She presupposes that male orgasm has a direct reproductive function--namely, to inseminate. But this conflates ejaculation and orgasm. Insemination is the function of ejaculation. Ejaculation and orgasm are actually distinct phenomena subserved by separate and dissociable physiological mechanisms. Ejaculation is all that's necessary for the function of insemination. So there's a problem about male orgasm: Why has it evolved? Clearly, the mechanisms subserving the sensation of orgasm are the evolutionary latecomers. So at some point in our evolutionary history, well before the emergence of Homo sapiens, there may have been non-orgasmic ejaculators and orgasmic ejaculators. Given where we've arrived, clearly the latter outreproduced the former. One possible reason is that orgasms drove the orgasmic ejaculators to have sex more often in order to induce the pleasurable sensation. The common early developmental pathway of males and females would have endowed females with the mechanisms for orgasm as well, as Lloyd herself shows, following [evolutionary psychologist] Donald Symons. Once so endowed, orgasm could have performed the same motivational role in women. In that case, in both sexes, orgasm would be an adaptation for a higher frequency of sex--hence, presumably, a higher rate of offspring production relative to our ancestors without the pleasurable sensation of orgasm. Of course, this is highly speculative, and--to repeat--I haven't made my way through all of Lloyd's arguments. But at first glance, I'm skeptical.

JRM: Do you think people tend to resist any evolutionary account of human behavior because it seems to reduce important aspects of our emotional lives--romantic and parental love, for example--to an impersonal desire for reproductive success?

DB: When we introspectively focus on the proximate cause of our behavior, we tend to think it's sufficient explanation of my getting married that I love this person, and that I have no desire to have children. So the idea that [reproduction] is a complete explanation sets up a resistance in a lot of people [to questions such as] why is it that these emotions have evolved, and what evolutionary function do they serve? That's actually a different kind of explanation. It's not an explanation of how proximate mechanisms function, but an explanation of why we have those kinds of proximate causes driving our behavior.

Even an evolutionary biologist like [the late Stephen Jay] Gould was prone to this slippage between proximate and ultimate explanations, and then to rejecting an ultimate explanation because of thinking a particular proximate explanation was sufficient. In Gould's critique of Evolutionary Psychology, he said, "I don't think that males are willing to rear babies only because clever females beguile us. A man may feel love for a baby because the infant looks so darling and adorable." Gould was slipping there between the proximate and ultimate explanations. The ultimate explanation is female sexual selection for care-giving males. The proximate explanation has to do with what causes males to respond that way to children, and that can be entirely because they look so adorable. That's not incompatible with an evolutionary account.

JRM: At the end of the book you spend a chapter arguing that there is no universal human nature. Can you explain what you mean?

DB: I go by what others have used the term to mean. If by human nature all you mean is whatever humans do, then absolutely there's a human nature, and an evolutionary perspective on human beings will inform us about human nature. But traditionally the concept of human nature has [been] a much more theoretically loaded concept, which is that there are certain things that it's normal for humans to be, and that constitute human nature. The concept of human nature [therefore] only refers to a partial subset of all of the manifest diversity that we view among human beings. And I think that notion has no foundation in evolutionary theory. That notion is in fact a vestige of 19th-century natural theology.

A truly evolutionary view of our species recognizes that variation is not some noise in the system, but is the system itself. And so in an important sense there's no such thing as the human mind, which an evolutionary perspective on will illuminate us about, but rather there are a variety of different kinds of minds out there, all of which have evolved, and in many cases the variety of kinds of minds are maintained by frequency dependent selection. In the nontrivial sense, there's simply no such thing as human nature if you take evolutionary theory seriously. What's common at one particular time in the [evolutionary] process won't necessarily be common at a different time in the process within the same species.

JRM: Does the idea of evolved differences between the sexes stand or fall with the Evolutionary Psychology paradigm?

DB: These are tentative answers. I don't think that it does stand or fall with Evolutionary Psychology, even though they have been the principal purveyors of the idea of evolved sex differences. I don't think there's good evidence for the sex differences that I examine most in the book, namely in the design features of the mind underlying jealousy and mate preference. The extent to which there's good evidence of evolved sex differences is actually my next book project.

JRM: What hope do we have of understanding how evolution shaped our minds?

DB: One approach is to work from the past forward, which is the approach taken by the Evolutionary Psychology paradigm; to try to think about the adaptive problems that drove human psychological evolution, and how ancient problems are reflected in the current design of the mind. But another approach is to work from the present backwards; to look at how humans make decisions regarding things like mating and parental care; to model, from an adaptive standpoint, the decision making that humans make in contemporary environments; and to try to get a fix on the nature of reasoning involved. If you can identify ways in which people are behaving in a highly adaptive manner, that can perhaps--perhaps--inform you about some of the evolutionary pressures that gave rise to it. But that's still always going to be a rather highly speculative step of the process.

Only when the community of researchers who are applying evolutionary theory to human psychology begin to broaden the ways in which they do that will good answers begin to emerge. And if my book can have any positive effect I would hope it would be to prompt people to think about alternative hypotheses and different ways in which evolutionary theory might inform psychology.

JRM: What value can philosophers add to science?

DB: I have no doubt that some readers are going to say that I've brought nothing to these issues, because philosophers should stick to what they know--namely, nothing. And there's an extent to which I agree with them. Philosophy as a field is not a body of knowledge to be known. What we philosophers do get trained for is analysis of reasoning. I think philosophers can contribute quite a bit to ongoing scientific research in this respect, becausc theory and evidence aren't tightly and obviously connected to one another. Evidence usually only speaks to theory after some tortured chain of reasoning to connect the two. And it's that tortured chain of reasoning [that] philosophers are trained to look at with a critical eye.

I'm not telling the world that everything in my book is right, so everyone should stop listening to evolutionary psychologists. I propose something different: Inform yourselves. Please. Go out and read the stuff by evolutionary psychologists and read my book, then make up your own minds about what you think is right and wrong. I think people should look at both sides before deciding.

Source: Scientific American July 2005 [accessed 30 December 2008]