AS A human, you are undoubtedly an animal, even if you do not always choose to think of yourself that way. Like other animals, you eat, breathe and mate. It is only 5m years since your ancestors parted evolutionary company with those of the chimpanzees, and only a couple of hundred thousand since modern humans left Africa to begin their conquest of the world.
You might therefore expect evolutionary biology to cast light on the essential nature of humans. If they are products of evolution, then ought not evolution help explain what makes them tick? In theory it should. But the track record of the purely biological approach to thinking and human behaviour is poor. A generation ago, thinkers as different as Desmond Morris, a British ethologist, and E. O. Wilson, a Harvard entomologist, began to offer explanations of humans in biological terms, with distinctly uneven results. Simple-minded applications of biological concepts like “pecking order”, “nesting instinct” and “alpha male” have achieved little but crude caricatures of human life, and nobody but committed enthusiasts was persuaded.
Yet the biological approach would not lie down. A new phalanx of biological thinkers is now emerging under the banner of “evolutionary psychology”. The name itself is due to two American academics, Leda Cosmides and John Tooby, and their message is that recent advances in cognitive science now make it possible to avoid the mistakes of earlier biologically inclined thinkers. The bible of this movement is a collection of essays they edited with John Barkow, “The Adapted Mind” (Oxford University Press). Their introduction to this book serves as a manifesto calling on psychologists, sociologists, anthropologists and economists to break free from outmoded tradition and to begin anew within the framework of Darwinian theory.
Popularisers have followed hard on the heels of the academics. Two of the most successful are Matt Ridley and Steven Pinker. Mr Ridley was science editor of The Economist, and in his most recent book, “The Origins of Virtue”, published by Viking two years ago, he sought the seeds of human altruism in life on the African savannah. Understanding the evolutionary pressures responsible for fellow-feeling, Mr Ridley believes, will help identify the kinds of society that best suit human beings.
Steven Pinker is even more ambitious. He is professor of psychology at MIT, and now rather better known as a telegenic author and magazine contributor: he wrote a short piece for the “Talk of Town” section in a recent issue of the New Yorker offering “an evolutionary explanation for presidents behaving badly”. Yet Mr Pinker has serious aims and his latest, much talked about book, “How The Mind Works” (Norton; Allen Lane), is modest neither in title nor scope. He starts fairly sedately, with chapters on hominid evolution and visual perception. But once into his stride there is no stopping him. By the end, he has offered evolutionary explanations for human emotions, personal relationships, humour, music, literature, art and religion.
Where psychology went wrong
What exactly is new about evolutionary psychology? Psychology is the key term here. Any serious account of human beings has to give a central place to their intellectual abilities. People have taken over the planet not because they are stronger or fiercer than other animals (they aren't), but because they are cleverer. This is where older biological approaches broke down. They had nothing to say about human intelligence, but portrayed people as doltish bundles of instincts.
The fault lay less in biology than psychology. Until fairly recently the dominant paradigm in psychology offered virtually no purchase for evolutionary theorising. From David Hume in 1750 to B.F. Skinner in 1950, it was more or less taken for granted that all intelligence is built on one simple mechanism, the association of ideas. Intelligent minds start as blank slates, and gradually build up a picture of the world from elements associated in our experience. Given this assumption, there was little to say about how evolution might have made people cleverer. The only answer was that it must have made them better at making associations, presumably by enlarging their brains. So claims about “nesting instincts” and “pecking orders” seemed beside the point. They left out what made you special: your superior associative abilities.
Psychology is not like that any more. Instead of viewing the brain as one big associative engine, an increasing number of psychologists now take it to be a bundle of “modules”, each dedicated to a different intellectual ability, and each pre-programmed with a substantial body of information about the world. A key moment was Noam Chomsky's attack on Skinner's associative account of language-learning. In a famous review of Skinner's theory in 1959, Mr Chomsky argued that associationism could not possibly explain human language. Children learn it too fast, and on such incomplete evidence, and there are so many odd parallels between different tongues, that the only plausible explanation is an innate and dedicated “language organ”, which grows in the brain, just as your heart grows in the chest.
Once Mr Chomsky had made this breach, the floodgates opened. Psychologists now postulate innate “modules” for any number of intellectual abilities. That new approach was codified 15 years ago by a philosopher colleague of Mr Chomsky's at MIT, Jerry Fodor, in “The Modularity of Mind” (MIT Press). Mr Fodor appealed in this book to a wide range of evidence to argue that many dedicated cognitive devices are part of an innate inheritance and embody assumptions that could not have been derived from experience. Some of the modules postulated by psychologists are unsurprising, such as a module for visually identifying physical objects, or for segmenting heard speech into words. But others are less obvious, like a module for face recognition, or for distinguishing animals from artefacts, or thinking about other people's minds and motives.
Now add Darwin to modules
Evolutionary psychology is what you get when you marry the modular view of the mind to the modern Darwinian theory of natural selection. Along with the modules, you get claims about the evolutionary purposes for which they were selected. In a way, it is surprising that this marriage has taken so long to arrange. One of the curiosities of modern intellectual life is that Messrs Chomsky and Fodor, the pathbreakers who believe that many intellectual capacities are innate, have nonetheless resisted the evolutionary approach to the mind. After all, the whole thrust of their modular revolution was that the brain contains a number of purpose-specific organs whose construction is directed by the genes. Despite that, the originators of the “nativist” revolution have from the start discounted attempts to plumb the evolutionary history of these organs.
One rather superficial worry may be that, once you start down the evolutionary path, you will end up concluding that intellectual differences between human groups are due to differences in their genes. However, evolutionary psychologists like Ms Cosmides and Mr Tooby have insisted all along that this is no part of their agenda. They are not interested in differences, but likenesses. Here they contrast themselves with social-scientific orthodoxy. Throughout this century, anthropologists and sociologists have emphasised cultural diversity. They have taken the wide spectrum of human arrangements to show that virtually any pattern can be imposed on the blank slate of human mentality by diverse cultural environments. A famous book epitomising this view was Margaret Mead's pre-war bestseller, “Coming of Age in Samoa”, which portrayed liberal South Sea sexual mores as an almost perfect inversion of strait-laced American conventions.
Ms Cosmides and Mr Tooby counter this model with the claim that cultural variation is much less wide than supposed. There are in fact no societies without marriage, sexual jealousy, humour, not to mention phrase-structure grammar. Of course, they concede, there remain many interesting differences between human societies. But just as interesting are the striking limits to this variation. A hero of the evolutionary psychology movement is Derek Freeman, an Australian anthropologist, who has argued that Samoan life is not so permissive after all, and that Mead was largely the gullible dupe of inventive informants.
The real question about human society, insist the evolutionary psychologists, is not why it varies, but why it stays so much the same. Their answer is that we humans have inherited a common set of psychological mechanisms from our evolutionary past. These mechanisms served specific functions as we evolved away from the chimpanzees. To comprehend ourselves fully, we therefore need to view ourselves as inheritors of intellectual abilities that proved useful to our hunter-gatherer ancestors in sub-Saharan Africa.
Of course, few humans live as hunter-gatherers any more. But, even so, say the evolutionary psychologists, the evolutionary perspective is crucial. Modern life is a product of stone-age minds and contemporary circumstances, and we will only get half the picture if we ignore our biological history.
One good illustration of this approach is the evolutionary psychologists' theory of human reasoning. Over the past couple of decades, evidence has been building up that humans are amazingly bad at solving simple logical problems. The “Wason selection task” is just one example from a huge body of experimental data. It involves cards with a letter on one side and a number on the other. Experimental subjects are asked which of the following four cards they should turn over to test the hypothesis that each vowel has an odd number on the other side: E, 3, 4, D. People are awful at this task. The right response is the first and third card, but only about 10% of normal subjects answer correctly. However, now consider a variant. Imagine you are at one of those discotheques where men must pay, but women do not have to. Everybody has a card indicating their sex on one side (M or F), and whether they have paid (P or not-P) on the other. Which cards—M, P, not-P or F—should you turn over to test whether the payment rule has been obeyed? With the problem recast in this way, many more people correctly pick the first and third cards. Even though the two tasks are structurally identical, somehow the new format makes the solution easier to see.
Ms Cosmides's theory is that this is because we have an ancestral cheater-detection module which evolved to identify those who go back on their promises. This module is intrinsically suited to the second problem, but not to the first. Of course, other explanations might strike you as equally plausible. Isn't the first problem just harder to understand than the second? But a series of further experiments conducted by Ms Cosmides suggest otherwise. The problem seems to remain hard even if posed in quite familiar terms, as long as it doesn't involve cheating, and to become easy as soon as the cheating element is introduced, even if in unfamiliar settings.
Biology, not behaviour
This cheater-detection theory illustrates a a selling-point of evolutionary psychology as against earlier biological approaches. The focus is now on underlying mechanisms, not observed behaviour, and the thesis is that these mechanisms once served a biological purpose, not that the behaviour now does. Thus, while your cheater-detection module works well as long as it sticks to its original context, there is no denying that it gets you into a mess when you try to use it to solve abstract modern problems. In the current jargon, your modules may all be “adaptations”, in that they evolved historically for a purpose, but they are not necessarily “adaptive” any more, for they can easily produce bad results in the modern world. Because of this, evolutionary psychology manages to avoid the more absurd excesses of those who tried to show that every idiosyncrasy of modern behaviour, from trainspotting to tourism, somehow helps to serve the biological ends of survival and reproduction.
Whether evolutionary psychologists manage to avoid all the mistakes made by their predecessors is less clear. Messrs Chomsky and Fodor are not the only critics with serious doubts. Few psychologists would any longer disagree that the mind contains many modules, and that this is in some sense a result of evolution. But many would deny that modules are all the mind is made of, and even more would query the value of speculation about long-lost evolutionary histories.
A double weakness
There are two worries here, one about evolutionary speculation and the other about the completeness of the modular view of mind. The first worry echoes the standard accusation that Darwinian enthusiasts are too quick to read historical purposes into every biological trait. In Stephen Jay Gould's telling phrase, they are overly fond of “just-so stories”, which differ from Kipling's fables only in their lack of good jokes. Mr Gould's immediate target here is “selfish-gene” theorists like Richard Dawkins, and it is a moot point whether he actually hits that mark. But, whatever you think of Mr Dawkins, evolutionary psychology is indeed open to the just-so charge. In principle it may seem a good idea for psychology and evolutionary theory to pool their intellectual resources. But given the paucity of hard evidence on each side, the merger often seems to achieve little more than an incitement to fabulation.
The trouble is not just that human brains leave no fossils, though this is certainly one problem. Just as hazardous is the lack of definite knowledge about current mental mechanisms. This makes it all too tempting to put evolutionary speculation in the place of hard psychological evidence, and so conjure mental modules out of historical myth. Take Ms Cosmides's theory about the evolution of a cheater-detection module. This is now widely accepted. But there is no independent evidence, apart from Ms Cosmides's psychological experiments, for this historical story. Moreover, other psychologists now claim to have performed new experiments which show that a cheating factor is not the crucial variable in the Wason selection task after all. Less indulgent critics will say that the flirtation with evolution has simply led Ms Cosmides up a theoretical blind alley.
A similar charge can be levelled at other prize exhibits in the gallery of evolutionary psychology. The theories of human altruism described in Mr Ridley's “The Origins of Virtue” involve any number of plausible ideas about the social practices of our hominid forefathers. But there is no real historical basis for these parables, and precious little direct evidence that today's humans display any corresponding dispositions. The ideas in Mr Ridley's book exhibit game-theoretical sophistication and much ingenuity, and are worth reading for that reason alone, but they scarcely qualify as reliable science.
Then there is sex. Reproduction is central to evolution, but there is room to wonder whether that explains the attention it gets from the more pop-oriented evolutionary psychologists. The leading light in this area is David Buss, or “The Doctor of Love”, as he is fondly termed on “The Evolutionist” web page. His book, “The Evolution of Desire” (Basic Books), reports the results of a questionnaire given to 10,000 people in 37 countries. In every country, women like rich men, and men like young attractive women. Mr Buss also explains that potential pick-ups start looking better as closing-time nears and worse again after sex. Well, maybe that is all so, and perhaps it has something to do with the evolutionary roles of the sexes. But Mr Buss tells you little about the precise mechanism behind the behaviour. Defenders of evolutionary psychology may reasonably reply that there are better practitioners than Mr Buss and more impressive examples of Darwinian accounts of human mental phenomena than singles-bar behaviour. Yet even the best samples of the evolutionary approach raise the question of its explanatory goal. Do the different examples, plucked here and there from the vast field of human mental life and behaviour, show promise of ever adding up to a coherent theory of the mind?
That question brings in the second main worry about evolutionary psychology: by emphasising the modules it leaves out the important part of the mind. Evolutionary psychologists often liken the mind to a Swiss Army knife. It contains a large number of purpose-built tools, each designed for a quite specific purpose. But this picture prompts an obvious question. Who, or what, is deciding when to open which blades? Don't you need some central intelligence to orchestrate the overall operation? Some evolutionary psychologists say no. But, while that may be true of other animals, it makes little sense for humans. For one thing, you seem to need a central intelligence to understand human moral reasoning. Even if your modules incline you towards sexual and racial discrimination, for example, it does not follow that such discrimination is either inevitable or justified. If humans are just a collection of modular reflexes, how is it that they can correct their inclinations? Humans seem to need some mental faculty that can stand back from modular promptings and tell them how to do better.
There are less elevated examples of people monitoring the outputs of their purpose-specific mental modules. You are often quite aware that your visual system is fooling you: for example, when you look at trick drawings, or indeed when you watch television. If it is possible to question modular inclinations in this way, there must be some place in the mind which transcends the modules.
To insist that there is more to the mind than modules is not to deny humans' animal heritage: no doubt a person's central intelligence is itself an evolutionary product of the past. But it does mean that evolutionary psychology, like its predecessors, is in danger of ignoring the very thing that makes humans different from other animals. Perhaps evolutionary psychologists will soon shift their focus away from peripheral modules, and start contributing to an understanding of the really hard biological problem of the structure and function of the central intellectual abilities. Until then, they are unlikely to shed more than a sidelight on the human mind or to show people much about why they live the way they do.
This article appeared in the Moreover section of the print edition under the headline "Biology isn’t destiny"
From the February 14th 1998 edition
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