Planet Earth

Ken Miller's Guest Post, Part Two

The LoomBy Carl ZimmerJan 3, 2009 12:32 PM


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As promised, here's Ken Miller's second post on intelligent design, following on yesterday's introduction. [And here's the third and final post.]

In Part 1, I showed that Casey Luskin’s charges with respect to my testimony in Kitzmiller v. Dover were completely false. Michael Behe did indeed argue, throughout his 1996 book, Darwin’s Black Box [DBB], that the “entire blood-clotting system” was “irreducibly complex,” and I cited examples from that book to prove it. Therefore, the existence of a living organism missing so much as a single part of that system was indeed a falsification of ID’s blood-clotting argument. Given that we now have examples of organisms (jawless fish) missing at least 5 components of that “irreducibly complex” system (see Doolittle et al, 2008), it’s perfectly obvious that Luskin’s attempts to rehabilitate that argument are hopeless. Ever the optimist, Part 2 of Luskin’s end-of-year project is to salvage Of Pandas and People, the creationist-turned-ID textbook that was at the heart of the Dover trial. Incredibly, in trying to accomplish this feat, he fails to understand the very argument he’s trying to prop up. What Luskin does not seem comprehend is that irreducible complexity is not an argument for design — it is an argument against evolution. Simply stated, when a system is labeled as “irreducibly complex,” the ID proponent is making a claim for the unevolvability of that system. The reason that such systems are said to be unevolvable is because their individual parts are supposedly nonfunctional until they are all combined into a single, working system. As Behe has said and written, “any irreducibly complex system that is missing a part is by definition nonfunctional” [DBB, p. 39]. As Behe further points out, since those parts are nonfunctional on their own, they could not have been assembled by evolution, because “…natural selection can only choose systems that are already working…” [DBB, p. 39]. That would be a powerful argument against evolution — if it were true. Unfortunately, it’s not, and the Dover trial demonstrated that for at least three of ID’s favorite systems, blood-clotting, the bacterial flagellum, and the immune system. By pointing out, in court, that individual parts of each of these systems do indeed have perfectly functional roles, we showed that Behe’s claim of unevolvability was false. (For details on the flagellum see Pallen & Matzke, 2006; the immune system, Bottaro et al, 2006; Jiang & Doolittle, 2003 present an evolutionary pathway for the blood-clotting system). Luskin, however, ignores Behe’s own logic and pretends that irreducible complexity is really an argument about whether parts of an established system are superfluous. In other words, to Luskin, the only way to show that a system is irreducibly complex would be to take a couple of parts out and see if it keeps working. That stunning error of logic is why he actually believes that pulling a wheel off my Trek road bike would demonstrate the irreducible complexity of the bicycle’s design. It’s also why he argues that it doesn’t matter that whales are missing one part of the clotting system, bony fish are missing three, and lampreys are missing (although he doesn’t seem to know this) five. As a result, the only evidence he says he’d accept for evolution would be a knockout experiment “that removed certain components from the blood-clotting cascade, and found that the blood still clotted properly.” But all that would actually show, of course, is that the system had superfluous parts. Luskin would then take a tiny step back and claim that what was left behind was still irreducibly complex. Incidentally, Luskin suggests that the lack of Factor XII in dolphins is the result of a “functional constraint” associated with the design of vertebrates living in water. That, he presumes, is why dolphins and jawed fish both lack Factor XII. In his view, “Darwinists” (like me) may believe that “dolphins are supposedly descended from land-dwelling vertebrates,” but that issue “will require further research to sort out.” Really, Casey? As I pointed out in my testimony at the Dover trial, the key reason why evolution is science is that it is testable. If dolphins and other cetaceans are indeed descended from land-dwelling mammals, their ancestors should have had the genes for Factor XII in their genomes. During the transition to water, those genes should have been deleted or inactivated, perhaps as an adaptation to deep sea diving, and today their traces might still be present in the cetacean genome, if only we care to look. Would you like to take a look and place a bet on the results of that “further research,” Casey? As much as I’d like to win a few bucks from my friends at the Discovery Institute, it wouldn’t be sporting, since such research was actually done more than a decade ago [Semba et al, 1998]. Whales possess a Factor XII pseudogene, an inactivated version of the very same gene carried by land-dwelling mammals. That pseudogene is a direct mark of their common ancestry with other mammals, and disproves any suggestion that constraints on cetacean “design” required the absence of Factor XII. Rather, ordinary genetic processes knocked out the gene, and today the pseudogene remains merely as evidence of their evolutionary ancestry. Like just about everything that comes out of the Discovery Institute, Luskin’s idea of evidence isn’t intended to advance scientific understanding — it’s only designed to score debating points. Unfortunately, it doesn’t do that, either. What Mr. Luskin clearly does not understand is that irreducible complexity is really an argument about how a system came to be, not whether it contains dispensable parts. And the argument, so clearly stated by Michael Behe in both of the books in question (Pandas and DBB) is that the whole system has to be assembled at once, in “one fell swoop,” because partial assemblies, containing just a few parts, are “by definition nonfunctional.” How do you test that assertion? By looking around in nature and seeing if partial assemblies of the more complex system do exist and are indeed functional. What happens when you do that? You already know the answer. From the bacterial Type III secretory system to the simplified clotting system of the lamprey, each of the favorite examples of the ID movement have collapsed under the weight of scientific evidence. Once you discover that the parts of the system do indeed have functions of their own, even in different contexts, you’ve answered the challenge from ID. As Behe pointed out, “…natural selection can only choose systems that are already working..” Yup. And that’s why once you’ve demonstrated that the parts of the system do indeed work just fine in other contexts, you’re answered the ID challenge fully and completely. Case closed. Three years ago, in fact. Case closed, and ID lost. Casey, if you really want to defend Michael Behe, a good place to start would be by reading him. Coming next:From reliving the past to the future of creationism. References: Pallen MJ, Matzke NJ. (2006). “From The Origin of Species to the origin of bacterial flagella.” Nature Reviews Microbiology, 4: 784-790. Bottaro A, Inlay MA, Matzke NJ (2006) “Immunology in the spotlight at the Dover 'Intelligent Design' trial.” Nature Immunology 7: 433 – 435. Doolittle RF, Jiang Y, Nand J. (2008) “Genomic evidence for a simpler clotting scheme in jawless vertebrates.” J. Mol. Evol. 66:185-96. Jiang Y, Doolittle RF (2003) “The evolution of vertebrate blood coagulation as viewed from a comparison of puffer fish and sea squirt genomes.” PNAS 100: 7527-7532 Semba U, Shibuya Y, Okabe H, Yamamoto T (1998) Whale Hageman factor (factor XII): prevented production due to pseudogene conversion. Thromb. Res. 90: 31–37.

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