A paper published in the Proceedings of the National Academy of Sciences makes the startling claim that all flagellar genes “originated through the successive duplication and modification of a few, or perhaps even a single, precursor gene” (see abstract below). While consistent with Darwinian evolution, such excessive hyperevolution was too much even for the hyperevolutionists at the Panda’s Thumb (go here), who are now distancing themselves from its conclusion. What’s going on here? How could people publish such a ridiculous result, and in PNAS of all places? Let me suggest the following hypothesis: Liu and Ochman, the authors of the piece, are really ID advocates who are pulling a Sokal-style hoax, pushing the envelope to see how extreme they can make their claims for evolution and still get them published. Inspired by Liu and Ochman, I have an article in the works for how the core components of human eye evolved through the successive duplication and modification of a few, or perhaps even a single, precursor gene in a primitive chordate ancestor. I may not be able to get anything published in the peer-reviewed biological literature that’s pro-ID, but something pro-evolution, if sufficiently extreme, is a different matter. Stay tuned.
Stepwise formation of the bacterial flagellar system
Renyi Liu * and Howard Ochman *
Departments of *Biochemistry and Molecular Biophysics and Ecology and Evolutionary Biology, University of Arizona, Tucson, AZ 85721
Elucidating the origins of complex biological structures has been one of the major challenges of evolutionary studies. The bacterial flagellum is a primary example of a complex apparatus whose origins and evolutionary history have proven difficult to reconstruct. The gene clusters encoding the components of the flagellum can include >50 genes, but these clusters vary greatly in their numbers and contents among bacterial phyla. To investigate how this diversity arose, we identified all homologs of all flagellar proteins encoded in the complete genome sequences of 41 flagellated species from 11 bacterial phyla. Based on the phylogenetic occurrence and histories of each of these proteins, we could distinguish an ancient core set of 24 structural genes that were present in the common ancestor to all Bacteria. Within a genome, many of these core genes show sequence similarity only to other flagellar core genes, indicating that they were derived from one another, and the relationships among these genes suggest the probable order in which the structural components of the bacterial flagellum arose. These results show that core components of the bacterial flagellum originated through the successive duplication and modification of a few, or perhaps even a single, precursor gene.