Dear Readers,At the end of his first post squabbling with Discovery Institute’s Casey Luskin, Brown University Professor Kenneth Miller refers to some great new work by UC San Diego Professor and member of the National Academy of Science, Russell Doolittle. Doolittle, of course, has worked on the blood clotting cascade for about fifty years! (I discussed some of his work in Chapter 4 of Darwin’s Black Box.) In a new paper Doolittle and co-workers analyze DNA sequence data from a primitive vertebrate, the lamprey, thinking that it might have a simpler clotting cascade than higher vertebrates. (1) It is difficult work, because the sequences of lamprey proteins — even ones that are indeed homologous to the proteins of other vertebrates — are significantly diverged from, say, mammalian proteins.
They argue that most of the core clotting cascade proteins are present, but two seem to be absent: lamprey has single proteins that act as Factor V/VIII (proaccelerin/anti-hemophilic factor) and Factor IX/X (Christmas factor/Stuart factor). The authors then infer that either gene or genome duplication led to separation of the factors. Although it’s interesting work, Doolittle’s conclusions are only suggestive (and the authors clearly say that the data are only suggestive). They found four copies of genes that are similar to Factors V/VIII, as well as to the non-clotting proteins ceruloplasmin and hephaestin (Figure 2 in their paper). They argue that only one is a real blood clotting factor and the other three aren’t, but the arguments are pretty tentative. The same for Factors IX/X. The authors identify two “Factor X” genes. Might one of those be acting as a Factor IX gene? At the conclusion of the paper the authors say they may try to support their arguments with biochemical experiments. I’m looking forward to reading the results of those.Whether or not their conclusion is correct, however, as far as the argument for intelligent design is concerned the only relevant part of Doolittle’s paper is Figure 10, which purports to show the clotting pathway in lamprey vs. other vertebrates. (Intelligent design is wholly compatible with common descent — including descent by gene duplication/rearrangement. Rather, ID argues against the Darwinian claim that complex, functional molecular systems could be built by a random, unguided process.) Yet to get from one arrangement to the other one would take multiple steps, not just one: whole genome duplication, retargeting of Factor IX, retargeting of Factor VIII, and so on. (The problems are essentially the same, as I pointed out in an essay in 2000 entitled “In Defense of the Irreducibility of the Blood Clotting Cascade,” posted on the Discovery Institute website.) So even if the suggested events occurred, they were extremely unlikely to have occurred by a Darwinian mechanism of random mutation/natural selection (the authors make no argument for a Darwinian mechanism). Guided, yes. Random, no.
It’s pertinent to remember here the central point of The Edge of Evolution. We now have data in hand that show what Darwinian processes can accomplish, and it ain’t much. We no longer have to rely on speculative scenarios that overlook barriers and problems that nature would encounter. Random mutation/natural selection works great in folks’ imaginations, but it’s a bust in the real world.
1. Doolittle, R.F., Jiang, Y., and Nand, J. 2008. Genomic evidence for a simpler clotting scheme in jawless vertebrates. J. Mol. Evol. 66:185-196.