Jerry Fodor, a philosopher at Rutgers, fairly recently (Oct. 2007) published an article in the London Review of Books entitled “Why Pigs Don’t Have Wings” in which he purports to provide a critique of the traditional Darwinian account of evolution. Here’s the link:

http://www.lrb.co.uk/v29/n20/fodo01_.html

Fodor is a pretty famous philosopher, especially in philosophy of mind, psychology, and cognitive science. He’s only recently been turning to thinking about philosophy of biology.

Fodor’s View

In short, Fodor argues that the traditional Darwinian account of the development of living things (phylogeny) has a flawed component. This component is adaptationism: the view that all the heritable traits of a species (phenotypes) are brought about by a process of adaptation: “the process by which environmental variables select among the creatures in a population the ones whose heritable properties are most fit for survival and reproduction.” I take the view to be the following: all the traits that a member of a species can inherit are there, able to be inherited, because they were at one point more advantageous to have for the earlier stage of the species than a competing trait. And “advantageous” here only means that it helps a member of that species to live to a reproductive age and reproduce. (So, superior strength and so on might be advantageous for a species, but needn’t.)

Fodor claims that there is a conceptual and an empirical problem with adaptationism. The conceptual issue, roughly, is that adaptationism may be too coarse-grained so that it cannot distinguish between (and so provide distinct explanations for) distinct phenotypes. Fodor’s example is a polar bear’s trait of having white fur versus the trait of having fur that matches it’s normal environment. The empirical issue is, roughly, that adaptationism cannot provide a better explanation in certain cases as certain alternative explanations. These two alternative explanations are evolutionary-developmental theory (evo-devo) and by-product theory (inspired by the idea of evolutionary spandrels).

Here’s a paragraph from the article that summarizes the main worry inspired by evo-devo (albeit perhaps in a hyperbolic way):

One can think of the Darwinian account of evolution as prompted by the question: why are some phenotypes more similar than others? Darwin’s answer was that phenotypic similarity is, pretty generally, explained by common ancestry; and the more similar two creature’s phenotypes, the less remote is the nearest ancestor that they share. There are isolated examples to the contrary, but there’s no serious doubt that this account is basically correct. And, if it’s not the best idea anybody ever had, it’s pretty good by any of the local standards. When you ask Darwin’s question – why are phenotypes often similar? – you do indeed get Darwin’s answer. But if you ask instead why it is that some phenotypes don’t occur, an adaptationist explanation often sounds somewhere between implausible and preposterous. For example, nobody, not even the most ravening of adaptationists, would seek to explain the absence of winged pigs by claiming that, though there used to be some, the wings proved to be a liability so nature selected against them. Nobody expects to find fossils of a species of winged pig that has now gone extinct. Rather, pigs lack wings because there’s no place on pigs to put them. To add wings to a pig, you’d also have to tinker with lots of other things. In fact, you’d have to rebuild the pig whole hog: less weight, appropriate musculature, an appropriate metabolism, an apparatus for navigating in three dimensions, a streamlined silhouette and god only knows what else; not to mention feathers. The moral is that if you want them to have wings, you will have to redesign pigs radically. But natural selection, since it is incremental and cumulative, can’t do that sort of thing. Evolution by natural selection is inherently a conservative process, and once you’re well along the evolutionary route to being a pig, your further options are considerably constrained; you can’t, for example, go back and retrofit feathers.

The main worry inspired by the idea of spandrels is that some traits might just be by-products or side-effects of adapted traits. Fodor’s example: tameness and aggressiveness in foxes have been shown to have other distinct phenotypes that come along for the ride when these are selected for by breeding. For example, floppy ears are typical of tamer foxes. So, suppose aggressiveness is more advantageous for wild foxes, does that mean that non-floppy ears that comes along with that is advantageous?

Responses

At the end of Fodor’s article are links to some responses by some philosophers and others, including Simon Blackburn, Philip Kitcher, and Daniel Dennett. Many of the responses are interesting, but I’d like to say something about the response of Jerry Coyne and Philip Kitcher. (Brian Leiter seems to think they’ve got a good critique of Fodor.)

Coyne & Kitcher respond to Fodor primarily by arguing that the alternatives that Fodor offers (evo-devo and by-product explanations) are additions to adaptationism that are consistent with it. As far as I can tell, this is right, but Fodor doesn’t seem to be denying it, or at least he needn’t. Fodor’s point seems to be that adaptationism isn’t going to explain all of phylogeny. He isn’t claiming that adaptationism is an entire failure (he admits several times that it gets a great deal right—see the paragraph I quoted above). His point is that we can’t simply keep making all these revisions to adaptationism and always continue to claim that it’s still a form of adaptationism. Suppose I claim that everything happens for my own benefit. Then any counterexample to that claim (an instance of something happening that doesn’t benefit me) makes that claim false. And isn’t adaptationism the view that all heritable traits of a species are brought about by the process of adaptation? So what about by-product traits like floppy ears in foxes? And what about the explanation of negative traits, such as not having wings? And what about coextensive traits, such as whiteness versus being the same color as one’s environment in polar bears? Why aren’t these counterexamples to adaptationism? Shouldn’t we say that some traits are explained by the process of adaptation, but some aren’t? And isn’t that to deny that adaptationism is the only explanation?

Anywho, I think Fodor and others here might have a legitimate worry about adaptationism being the only explanation of heritable traits. It’s an interesting issue.

Note: This sort of critique of adaptationism is not some critique of evolution as a whole that creationists or others can co-opt or anything. Fodor and others agree that we (and other species) evolved. This is a debate about what the mechanism or mechanisms are that underwrite the process of evolution.

Update

I’m not trying to defend Fodor to the death here; I don’t know much about philosophy of biology. But, here’s further evidence, I think, that Blackburn and others are not understanding Fodor’s view here (Blackburn and the gang collectively object to Fodor and Fodor replies):

http://www.lrb.co.uk/v30/n01/letters.html#letter5

Where, for example, do Blackburn and gang get the idea that Fodor says there is no fact of the matter regarding “the question of whether it was the whiteness of polar bears or their blending in with their surroundings that was ‘selected for’”? Fodor explicitly states that he is not arguing this.

Alas, for some reason, Brian Leiter keeps acting like Fodor is some lunatic.

Trackback URL