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The Human Nature Review Human Nature Review  2002 Volume 2: 378-381 ( 17 September )
URL of this document http://human-nature.com/nibbs/02/palmer.html

Book Review

Evolutionary Psychology: The Ultimate Origins of Human Behavior
by Jack A. Palmer and Linda K. Palmer 
Boston: Allyn and Bacon, 2002

Reviewed by Neil Levy, Centre for Applied Philosophy and Public Ethics, University of Melbourne, Parkville, Victoria 3010, Australia.

Evolutionary psychology (EP) is barely a decade old, yet already there are several textbooks available designed to give students an overview of the discipline. This is a worthy addition to the range. Its ten chapters cover most of the issues and information required by students of EP, from an overview of Darwinian theory and its synthesis with genetics, to its applications to understanding mating strategies of contemporary human beings. It is, for the most part, well-written and clear (though it shows signs of careless computer-generated spell-checking), and it is frequently fascinating. How successful is it overall? The answer to this question depends on what one believes the aim of a textbook should be. If you think textbooks should strive to communicate clearly an overview of the general state of play in a field, then it succeeds admirably. But if you think a textbook should be generally free of significant obscurities and confusions, then it fails. Palmer and Palmer’s confusions and obscurities are not unique to them: they are those of their field.

EP, Palmer and Palmer tell us, is ‘the study of the adaptive significance of behavior’ (xiii). Despite its youth (at least as a self-conscious approach to the science of the mind), it already has its own journals, textbooks and the other trappings of a vigorous and confident academic discipline. However, EP is not a yet a unified approach to human psychology, still less, as its advocates often promise, the one approach that is capable of unifying all the social sciences. At this point in its young life, EP is a hodgepodge: a mixture of promising, well-designed research projects testing interesting hypotheses, popular magazine level speculation, of hard science - much of it only tangentially psychological - and just-so stories. Some of these confusions are relatively superficial and, we might hope, easily dispelled, but others go much deeper. We shall not be able to assess the promise of EP until its best practitioners sort through them, and give us an account of just what it is that is distinctive about their approach to the human mind and what its central claims consist in.

EP, like sociobiology before it, is widely hated and feared by practitioners of neighboring disciplines, especially the adherents of what Cosmides and Tooby call the Standard Social Sciences Model (SSSM). Its defenders frequently cry foul over the stream of vituperation directed at them, claiming that their critics misunderstand them and their science, and arguing that their work deserves a respectful hearing (it must be said, however, that EP advocates give back as good as they get - witness the contempt Palmer and Palmer heap upon an unnamed Stephen Jay Gould, whose only expertise, they contend, is in the paleontology of snails. EP is an irreducibly interdisciplinary research program, and it dismisses those whose training is primarily in one or other subfield of evolutionary science at its peril). One possible reason for this fear is the imperialist ambitions of the science. Not only does it attempt to invade the territories which other social scientists might wish to preserve as their own, it often uses their own methods and findings. It dismisses the SSSM as naïve, and then advances conjectures typical of that model as proof.

For instance, Palmer and Palmer explain human status seeking, conservatism and radicalness not just in terms of (say) sexual selection, but also birth order, utilizing Frank Sulloway’s research for this purpose. But the claim that birth order affects personality seems to be a typical SSSM claim: it advances predictions based on aspects of human social arrangements, not on their biology, evolved or otherwise. In the same vein, the claim that art has an adaptive purpose because it helps cements social bonds seems to be essentialist a functionalist explanation, of the kind anthropologists have been suggesting for the past seventy-five years. The feeling among adherents of the SSSM that they are being dismissed a little too quickly is understandable, to say the least, in the light of these claims.

If EP threatens to spill over beyond its self-proclaimed borders into the territory of the SSSM - territory which, it officially claims, is infertile and therefore best ignored - it also threatens to expand into the areas of the natural sciences. Its practitioners have a tendency to proclaim as their own any phenomenon the existence of which might be predicted on Darwinian grounds. Thus Palmer and Palmer devote many of their pages to discussing physiological phenomena, such as sperm competition and mother-fetus conflicts. Since EP is supposed to be concerned with behavior, it is hard to see how the struggle between mother and fetus for glucose is its territory.

These flaws, the uncertainty of the boundaries of the subject typical of EP and exemplified by Palmer and Palmer, are the least serious of the discipline. They betoken nothing more than an insecurity about the identity of a young discipline, and we might expect them gradually to dissipate. More serious are the problems internal to what is indisputably the territory of EP. At its best, EP produces impressive results, but it is seldom at its best. Its results are impressive only when two conditions are met: 

(a) it formulates a surprising hypothesis, on the basis of the postulated adaptive significance of observed or predicted behavior, and

(b) it develops methods which tend, with some high degree of probability, to confirm or deny the hypothesis. 

Some of its work on mating strategies meet these conditions. For instance, the hypothesis that some women have affairs in part because they have an evolved predisposition to pursue a mixed mating strategy, whereby they marry a mate who will provide for them and their children, while seeking better genes when the opportunity arises, generates the prediction that women will tend to have affairs with men who are more attractive than their long-term partners, will tend to have more orgasms with lovers than with their partners, will tend to be more likely to engage in intercourse with lovers during ovulation, and so on. EP advocates claim that these predictions are verified by their empirical studies. In any case, it is clear what kinds of evidence would count as confirming or falsifying the prediction. Of course, verifying the prediction will not be sufficient to confirm the mixed strategy hypothesis, for it may that we can advance another interpretation of the data, but formulating hypotheses clearly in this manner, and specifying what counts as confirming them, allows the debate to proceed with a maximum of clarity.

Too many of the hypotheses of EP come nowhere near meeting these standards. Hypotheses are often far from surprising. Instead, they are frequently clichés. The finding, for instance, that men place a high value on the attractiveness of short-term sexual partners is not surprising. Nor is it very interesting, since it is compatible with too many rival explanatory frameworks. When hypotheses are surprising, they are very often no more than speculations. For instance, Palmer and Palmer devote one chapter to personality and psychopathology, in which they suggest that personality disorders might be adaptations. It is possible, they point out, to imagine circumstances in which neuroticism, psychoticism, even schizophrenia, might be adaptive. Indeed it is, but this hardly amounts to evidence that these disorders are adaptations. Almost any behavior could be adaptive under the right circumstances, but it is likely that some are simply malfunctions. Until EP advocates can suggest a means of testing the hypothesis that these disorders are adaptations, they do better to refrain from such unproductive speculations.

On the face of it, the coexistence within EP of relatively well formulated and testable hypotheses with wild speculation backed up by just-so stories seems, like its uncertainty as to its boundaries, to be a relatively easily corrected flaw. Just as greater clarity about its boundaries will avoid the first set of problems, so greater clarity about its aims and methods will avoid the second. But such clarity is rarely forthcoming from EP advocates. Nowhere, in this book or, so far as am I aware, elsewhere in the corpus of EP is there a clear statement of what its basic claims about the human mind actually are. Instead, we must extrapolate these claims from individual instances of EP explanation.

There appear to be two basic set of claims, the relationships between which, and the relative importance of which, are obscure. The first is the claim, associated especially with Cosmides and Tooby and Steven Pinker, that the human mind is modular. According to this claim, we do not each possess a general purpose computer (as advocates of the SSSM allegedly believe) which can be applied to any problem with equal ease. Instead, our minds are sets of purpose-built tools, each of which is designed to solve a particular kind of problem. This is the kind of claim Cosmides and Tooby attempt to vindicate using the Wason Selection Tasks (reprinted as an appendix here, and discussed in the main text), in which subjects are tested to see how well they solve various inference problems. These problems are all of the same logical form, but, Cosmides and Tooby claim, we are much better at solving them when they concern social cheating than when their topic is something of less direct concern to us. From this fact they conclude that the human mind contains an inbuilt cheater detection mechanism. Perhaps more convincing evidence for the claims of modularity come from studies of patients with neurological damage, and fear association tests, in which it was apparently found that certain stimuli tend to be highly salient for primates including human beings.

The claim that the human mind is modular seems quite separate from another claim, implicit in a great deal of EP: that our fundamental desires can best be explained as the product of adaptations. This claim might best be approached from within belief-desire psychology, the central claim of which is that human behavior is typically explained as action which the subject believes will be instrumental to their satisfying their desires. From this perspective, EP might be seen as providing us with an explanation of why we possess the fundamental desires we do. Why do human beings find the taste of sugar pleasant? Because finding sufficient calories was a constant challenge in the environment of evolutionary adaptation, and therefore organisms who acted on proximate mechanisms which motivated the consumption of calorie containing foods were at an advantage compared to those who did not. Thus, evolution has left with a set of desires - for sexual intercourse, for food, aesthetic preferences and standards of beauty - which are innate in each of us.

These are quite different mechanisms, which would yield quite different predictions and have quite different implications. Importantly, they would seem to have different implications for the social and political questions which concern many of EP’s critics. It would seem, on the face of it, that modularity would be much less conservative in its implications than the desire theory, for modularity does not yield predictions about what we are programmed to prefer. Of course, it might be the case that both hypotheses are true: that our minds are modular, and that we have innate desires which are the product of evolution. But separating and clarifying these suggestions is the first, indispensable, step toward testing them.

In particular, advocates of EP owe us a clear statement of just what would confirm the hypothesis that our fundamental desires are the products of evolution. They are quick to deny that they are ‘genetic determinists’, but if they do not mean to suggest that our desires are determined by our genome, what do their claims here amount to? David Buss suggests somewhere that men can no more cease finding younger women attractive then human beings generally can cease finding sugar sweet, which seems to imply genetic determinism (that is, determination by normal genomes under standard environmental conditions) of preferences, if not actions. Some of the language employed by Palmer and Palmer suggests that preferences are not determined directly; instead, what is innate is a conditional strategy, which will be triggered by environmental conditions. This might be a fruitful direction to explore, though it is easy to see how the conditional strategy hypothesis might become vacuous: if it yields the prediction that we are innately programmed to prefer whatever it is in our interests to prefer in the circumstances.

This is a book which has much to recommend it. Its great strength is that it is generally representative of EP as a whole. This is also its fundamental weakness. It reflects not only the best and most productive findings of EP, but also its confusions and lack of clarity about its fundamental aims and claims.

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© Neil Levy.


Levy, N. (2002). Review of Evolutionary Psychology: The Ultimate Origins of Human Behavior by Jack A. Palmer and Linda K. Palmer. Human Nature Review. 2: 378-381.

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