Another ID Argument Doesn’t Stand Up to Scrutiny
Over at casa de Dembski, DaveScot tries to debunk a debunking of an ID argument. It goes something like this:
Michael Behe: The bacterial flagellum is irreducibly complex, that is, all of its components need to be in place before it’ll work. It can’t have evolved by gradual addition and improvement, because none of the subparts do anything until they’re all put together.
Nick Matzke: Ah, but the Type Three Secretory System (TTSS), a sort of bacterial syringe, is made up of proteins that look an awful lot like ones used in the flagellum. That is, you can build something useful using just some of the parts requied for a flagellum, and that gives natural selection something to work with. For instance, the flagellum could have evolved by adding parts to a TTSS.
DaveScot: Ah, but I have here a paper about a species of bacterium that started out with a flagellum, but lost most of its parts through natural selection, leaving only the parts needed to construct a TTSS.
To which I reply below the fold.
This is a red herring: Behe’s original claim that the flagellum is irreducibly complex (IC) and therefore could not have evolved rests on the assumption that natural selection cannot select for any subset of its components, since none of them do anything useful.
Matzke effectively demolished that assumption by showing that at least one subset of the flagellum’s parts—specifically, those used for building the TTSS—are useful, and therefore natural selection could have provided those parts as something to build upon to make a flagellum.
DaveScot’s paper, then, doesn’t demolish Matzke’s argument. At best, it weakens it a tiny bit (if we assume that the TTSS is the only possible useful subassembly of the flagellum; this seems dubious, because in nature, there’s very rarely just one of anything; if one subassembly is useful, it seems likely that another is, as well).
Shorter version:
Behe: Evolution of the flagellum could not have happened.
Matzke: Yes it could. For instance, TTSS.
DaveScot: But that’s not how it did happen.
Or try a different argument with the same structure:
Behe: Mormons could not have walked from New York to Utah in the 19th century. It’s simply too far. So they must have been airlifted.
Matzke: Actually, they could have walked from New York to Iowa, and from Iowa to Utah. You’ll concede that neither one of those trips is too far to walk.
DaveScot: Ah, but historical evidence shows that that’s not the route they took.
Just in passing, I wouldn’t mind seeing a diagram of this argument, since I’m refuting DaveScot’s refutation of Matzke’s refutation of Behe.