Wednesday, May 28, 2008

Evolutionary psychology: A "motley navy" of speculations, soon to be stranded?

Philosopher Jerry Fodor shares my skepticism of "evolutionary psychology", and explains why in "Why Pigs Don't Have Wings":
The years after Darwin witnessed a remarkable proliferation of other theories, each seeking to co-opt natural selection for purposes of its own. Evolutionary psychology is currently the salient instance, but examples have been legion. They’re to be found in more or less all of the behavioural sciences, to say nothing of epistemology, semantics, theology, the philosophy of history, ethics, sociology, political theory, eugenics and even aesthetics. What they have in common is that they attempt to explain why we are so-and-so by reference to what being so-and-so buys for us, or what it would have bought for our ancestors. ‘We like telling stories because telling stories exercises the imagination and an imagination would have been a good thing for a hunter-gatherer to have.’ ‘We don’t approve of eating grandmother because having her around to baby-sit was useful in the hunter-gatherer ecology.’ ‘We like music because singing together strengthened the bond between the hunters and the gatherers (and/or between the hunter-gatherer grownups and their hunter-gatherer offspring)’. ‘We talk by making noises and not by waving our hands; that’s because hunter-gatherers lived in the savannah and would have had trouble seeing one another in the tall grass.’ ‘We like to gossip because knowing who has been up to what is important when fitness depends on co-operation in small communities.’ ‘We don’t all talk the same language because that would make us more likely to interbreed with foreigners (which would be bad because it would weaken the ties of hunter-gatherer communities).’ ‘We don’t copulate with our siblings because that would decrease the likelihood of interbreeding with foreigners (which would be bad because, all else being equal, heterogeneity is good for the gene pool).’ I’m not making this up, by the way. Versions of each of these theories can actually be found in the adaptationist literature. But, in point of logic, this sort of explanation has to stop somewhere. Not all of our traits can be explained instrumentally; there must be some that we have simply because that’s the sort of creature we are. And perhaps it’s unnecessary to remark that such explanations are inherently post hoc (Gould called them ‘just so stories’); or that, except for the prestige they borrow from the theory of natural selection, there isn’t much reason to believe that any of them is true.

The high tide of adaptationism floated a motley navy, but it may now be on the ebb. If it does turn out that natural selection isn’t what drives evolution, a lot of loose speculations will be stranded high, dry and looking a little foolish. Induction over the history of science suggests that the best theories we have today will prove more or less untrue at the latest by tomorrow afternoon. In science, as elsewhere, ‘hedge your bets’ is generally good advice.

I have no problem (and am sure Fodor does not) with assuming that many features of our psychology are a result of our evolution. For example, the disproportionate tendency of humans to be right-handed rather than left-handed probably explains why so many languages associate the right side with things that are right or dexterous and the left side with things that are sinister or gauche or - if you like - left behind.

The problem with the "just-so" stories of evolutionary psychology is that - as Fodor implies in his entertaining passage - the evolutionary psychologist seizes on a given trait noticed in contemporary society and makes up a story about how that trait may have been useful in the Stone Age. That's "adaptationism." But the reality is that, in most cases, we have no idea whether the trait even prevailed in the Stone Age, let alone whether conditions then actually favoured it. There is nothing unusual about people preferring to do things that do not particularly benefit them or their children, for a variety of reasons.

The underlying assumption of evolutionary psychology is that people do not simply make decisions about what feels right, but are programmed to behave in certain ways by their genes. Believe that at your peril.

Apparently, there will be a big meeting at Altenberg, Austria, this July, to discuss what is wrong with adaptationism in general. Maybe we will be seeing fewer stories about, for example, the Big Bazooms theory of evolution, but don't count on it.

Oh, and why pigs don't have wings? Because, you see, winged she-pigs outran the he-pigs that were pursuing them, so the he-pigs only caught up with the ones that didn't have wings, so the "wingless" trait was passed on to all the little piglets. And our Stone Age ancestors witnessed the last of the transition, when there were still a few flying pigs around but not many, hence the expressing "when pigs fly." And if you think that's ridiculous, see the Big Bazooms theory, and don't miss Fred Reed's hilarious take on it ("Darwin and Banana Boobs").

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