![]() Gould used to argue against the instinctive resort to "adaptionist" explanations not every feature of biology or evolution, he argued, was an adaption. You've got to love the last sentence, which is worth repeating: "We speculate that a common, as yet unknown, genomic cis-regulatory architecture governing neck ossifications in tetrapod ancestors might have predisposed different descending tetrapod lineages to similar parallel trends." This is almost starting to sound like teleological evolution-but of course that's not allowed in Darwinian thinking, so it's just by the luck of the draw that all of these taxa independently arrived at the same bone structure.Now, Stephen J. Luskin goes on to note some further oddities of the homologies in vertebrate skeletons, such as the apparent loss, on multiple occasions, of the cleithrum, the major shoulder bone of primitive tetrapods, in different tetrapod groups (frogs still retain it, though salamanders don't, and many ancient amniotes did, though no modern amniotes do): ![]() Luskin can't quite get his head around the point that just because bones are more likely to be preserved than muscles or genes, they don't have to be directly inherited rather than effects of things that are directly inherited (of course, as Upton Sinclair noted of some other people, his salary depends on not understanding certain things). Interestingly, David Klinghoffer has a post on EN&V today that makes just this point: the genome isn't literally a "code" or blueprint (how exactly this makes the case for intelligent design is not quite clear). Matsuoka is suggesting that rather than trigger bone development directly, genes trigger muscle development in such a way as to promote bone development, with some interspecific variation in exactly how they accomplish this. ![]() Genes are not literally blueprints there is no gene for a scalpula located right next to the genes for the clavicle or cervical vertebrae. Vertebrates, after all, don't literally inherit their bones, or muscles, or nerves, or other body parts they inherit genes, which interact with cellular mechanisms to grow all these parts. But it's not entirely clear what is so "bizarre" about it. The rather counterintuitive "scaffold model" perceives muscle connectivities as the basic units (because they precisely correspond to cell populations) but considers the bones that everyone can see as mere epiphenomena and subjects of change.Luskin mocks this as a "bizarre" conclusion, forced by Matsuoka's slavish adherence to the dogma of common ancestry. Matsuoka, rather than reject the idea that the detailed similarity in form, location, and embryology of the neck muscles are homologous, proposes a startling idea: Luskin notes that Matsuoka notes a bizarre feature of embryonic development across species: the development of muscles from particular groups of cells is far more consistent ("more conserved") than are the actual bony sites to which they attach. The second, which takes up most of his article, is that Matsuoka's research throws a monkey wrench into the whole idea that homology is a result of common ancestry (actually, it's not quite clear whether Luskin means to attack the whole idea of homology - which was identified by creationist biologists before evolution was invoked to explain it - or just "Darwinian" explanations of it). The first is that Matsuoka's research doesn't depend on the assumption of common descent, and could be done simply on the basis of comparative anatomy. This, in turn, the Nature editors state, gives us insights into the evolution of the various parts of the skeletons of modern vertebrates. The paper describes Matsuoka's research into which parts of the skeleton originate from the neural crest cells formed in the outermost of the three layers (the ectoderm) of the developing embryo, and which parts originate from the mesoderm, the middle layer. This is not "blogging on peer-reviewed research " this is blogging on tendentious carping about a popularization of peer-reviewed research. This is an excessively recursive post: my review of Casey Luskin's review (on the Evolution News & Views website) of Henry Gee's, Rory Howlett's and Philip Campbell's review (in Nature) of a scientific paper by Toshiyuki Matsuoka et al.
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