More Denton: unlikely transitions (Introduction)

by David Turell , Saturday, April 18, 2015, 23:26 (3507 days ago) @ David Turell

Fins to limbs looks really impossible, as do scales to feathers, and angiosperms (flowering plants), like the Cambrian animals have no antecedents:-http://inference-review.com/article/evolution-a-theory-in-crisis-revisited-part-two-Either an IM is extraordinarily inventive or it is guided. Note 'apoptosis' is 'regulated cell death', deleting cells to make a finished product. This is a key concept. The whole essay is fascinating.-Fin to limb:-"Thirty years have passed. We have still not found a single fossil with an appendage that might have bridged the gap between a fish fin and the tetrapod limb. Certainly, since 1985, a great number of early amphibian fossils have been discovered, including Acanthostega, Tulerpeton, and Ventastega, as well as several fossil fish close to the fish-amphibian boundary, including the celebrated Tiktaalik. We have also made huge advances in understanding the developmental genetics of the limb. But we are no closer to giving an account of the fin-to-limb transition in Darwinian terms."-Scale to feather:-"Many of the genes and developmental systems utilized in feather morphogenesis, such as the pattern-forming genes Shh and Bone morphogenetic protein 2, or BMP-2, predated the origin of the feather. Both are widely utilized in the development of hair, limbs, digits, and teeth.30 During feather development, as Prum and Brush pointed out in another paper, the two so-called toolkit proteins, Shh and BMP-2, “[w]ork as a modular pair … The Shh protein induces cell proliferation, and the Bmp2 protein regulates the extent of proliferation and fosters cell differentiation.”31 The two proteins are used repeatedly throughout feather development from the initial formation of the placode to the pattern for the helical growth of the barb ridges.32 These remarkable developmental genetic advances, while providing evidence that the origin of the feather involved the redeployment of existing gene circuits, provide no support for the claim that the redeployment was the result of gradual micro-evolutionary processes."-The "plant bloom" ( its nickname):-"The sudden appearance of the angiosperms, I observed in Evolution, “is a persistent anomaly which has resisted all attempts at explanation since Darwin's time.”43 How true. No real flowers are found in any group of plants save those extant today, and no putative ancestral group has been identified in the fossil record, or by molecular phylogenetics. There is no universally accepted set of transitional forms leading up to earliest angiosperms."