Thursday, April 28, 2005

Unintelligent Analogies

PZ Myers has written an interesting post denouncing the use of analogy by proponents of "intelligent design" (ID). Now, analogies are routinely used by scientists in the process of developing and explaining their ideas. Some might even argue that scientific reasoning is mostly analogical in nature, although I think that largely misses the point. The point is that IDers spend most of their time developing, defending, and arguing about analogies between biological systems and everything from clocks to outboard motors, and little or no time actually studying biological systems in the field, the lab or at the computer. IDers are particularly enamored with analogies between organelles (organs of cells) and machines. For example, Michael Behe, one of the few biological scientists in the ID movement, used it in a recent Op-Ed article in the New York Times. He even tried to give the impression that mainstream cell biologists, like Bruce Alberts (President of the National Academy of Sciences and author of perhaps the most widely read textbook on cell biology), shared his half-baked ideas. That turned out to be a mistake, of course: Alberts was quick to dismiss Behe's claims. Behe is also famous for proposing an analogy between biological systems and mousetraps to illustrate the idea of "irreducible complexity" (IC). The analogy (and the whole concept of IC) is obviously flawed: for example, look at this priceless demonstration of how a single piece of wire could, in principle, evolve into a full featured mousetrap. So what did Behe do? Dash to the lab and do some experiments to demonstrate that there actually is such a thing as an IC organ or organelle or molecule? No, he went and wrote increasingly confusing (and confused) justifications of the analogy.

And this is precisely why scientists have no time for the drivel that comes out of the Discovery Institute and other creationist organizations, no matter how many PhDs, MDs or lawyers are behind it. If I tell you that a certain protein has evolved under the action of positive natural selection, any analogies I might make to windsurfing or mountain climbing are completely irrelevant. If I don't show you data on dN/dS ratios, McDonald Kreitman tests, gene genealogies, structural predictions, analyses of mutant forms, etc, you have every right to dismiss my assertions. Until IDers spell out how we might go about telling "intelligently designed" molecules from those evolved through the action of mutation, natural selection and genetic drift, don't expect me to pay any attention to what IDers have to say. Until then.