Evolution: Still a Theory in Crisis By: Michael Denton
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╝ Evolution: Still a Theory in Crisis By: Michael Denton ]1[ 1. Introduction One is the term “homolog.” As I use it, this term refers to a unique biological characteristic or trait shared by all the members of a particular group such as the pentadactyl ground plan of the tetrapod limb shared by all tetrapods. A homolog is therefore a “taxa-defining novelty.” The term homolog is used frequently by researchers in evolutionary developmental biology (evo-devo) to describe such character traits.8 Systematists often describe homologs as “synapomorphies” or “apomorphies”9 In the nineteenth century, Richard Owen termed them “primal patterns.”10 [ 8. Günter P. Wagner, Homology, Genes, and Evolutionary Innovation (Princeton: Princeton University Press, 2014). 9. Colin Patterson, “Morphological Characters and Homology,” in Problems of Phylogenetic Reconstruction, edited by Kenneth Alan Joysey and Adrian E. Friday (New York: Academic Press, 1982), 21–74; Patterson defined homology as synapomorphy, 29 (see reference to Patterson in Wagner, Homology Genes and Evolutionary Innovation, 74–75); a synapomorphy is a homolog shared by two or more taxonomic groups inherited from a common ancestor (the pentadactyl limb in various tetrapod groups); an apomorphy is a homolog shared by the members of a particular group but not present in an ancestral form (hair in mammals); Ian J. Kitching, Peter L. Forey, Christopher J. Humphries, and David M. Williams, Cladistics: The Theory and Practice of Parsimony Analysis, 2nd ed., The Systematics Association Publication No. II (New York: Oxford University Press, 1998), Chapter 1, 2–3. 10. Richard Owen, On the Nature of Limbs (London: John Van Voorst, 1849), https://archive.org/details/Owen1849br46D.] [Michael Denton: Evolution, Still a Theory in Crisis (Kindle Locations 146-151). Discovery Institute Press. Kindle Edition.] The other word I need to define is “non-adaptive,” which I also employ throughout the book. I use this term to refer to any feature or characteristic of an organism which does not appear to serve any conceivable specific adaptive end—in other words, any feature that makes no contribution to the fitness of the organism. Such features are invisible to natural selection because natural selection only sees traits which serve some adaptive end. Examples might be the shape of a maple leaf (a non-adaptive feature ]2[ restricted to an individual species of plant) or the pentadactyl limb (an example shared by many thousands of different vertebrate species). [Michael Denton: Evolution, Still a Theory in Crisis (Kindle Locations 152-156). Discovery Institute Press. Kindle Edition.] My major goal in this new book is to review the challenge to Darwinian orthodoxy and the support for typology provided by the novelty and extraordinary invariance of the homologs. In addition, I will explore how the adaptive status of many homologs is clearly in doubt. [Michael Denton: Evolution, Still a Theory in Crisis (Kindle Locations 157-158). Discovery Institute Press. Kindle Edition.] These two diametrically opposed conceptions of organic order were referred to by Stephen Jay Gould in his magisterial The Structure of Evolutionary Theory: Most organisms are well adapted to their immediate environments [conditions of existence], but also built on anatomical ground plans that transcend any particular circumstance. Yet the two principles [functionalism or structuralism] seem opposed in a curious sense—for why should structures adapted for particular ends root their basic structure in homologies that do not now express any common function (as in Darwin’s example of mammalian forelimbs)? The designation of one principle or the other as the causal foundation of biology virtually defines the position of any scientist towards the organic world and its causes of order... Shall we regard the plan of high-level taxonomic order as primary, with local adaptation viewed as a set of minor wrinkles… upon an abstract majesty? Or do local adaptations build the entire system from the bottom up? This dichotomy set the major debate of pre-Darwinian biology.12 [11. Stephen Jay Gould, The Structure of Evolutionary Theory [henceforth SET] (Cambridge, MA: Belknap Press [Harvard], 2002), p252.] [Michael Denton: Evolution, Still a Theory in Crisis (Kindle Locations 161-170). Discovery Institute Press. Kindle Edition.] Structuralism: According to the structuralist paradigm, a significant fraction of the order of life and of every organism is the result of basic internal constraints or causal factors that arise out of the fundamental physical properties of biological systems and biomatter. In other words, biological order that does not result from adaptation to satisfy functional ends. [Michael ]3[ Denton: Evolution, Still a Theory in Crisis (Kindle Locations 171-173). Discovery Institute Press. Kindle Edition.] Functionalism: According to the opposing paradigm, often referred to as functionalism, the main or sole fundamental organizing principle of biology is adaptation. On this view, the main Type-defining homologs (pentadactyl limb, etc.) are adaptations built by cumulative selection during the course of evolution to serve various adaptive ends. Biological order built in this way is contingent in the sense that it is undetermined by natural law. [Michael Denton: Evolution, Still a Theory in Crisis (Kindle Locations 242-246). Discovery Institute Press. Kindle Edition.] It is hard to imagine two scientific frameworks as diametrically opposed as structuralism and functionalism. Where functionalism suggests that function is prior and determines structure, structuralism suggests that structure is prior and constrains function. [Michael Denton: Evolution, Still a Theory in Crisis (Kindle Locations 251-253). Discovery Institute Press. Kindle Edition.] Since Evolution: A Theory in Crisis was published, there have been massive advances and discoveries in many areas of biology, including paleontology, genomics, and developmental biology. In 1985 the genome project was just launched, and researchers in developmental biology were just beginning to apply the new genetic knowledge to provide a detailed molecular genetic description of development. The new field of “evo-devo” (evolutionary developmental biology) was just emerging, as were the first hints of a new epigenetic paradigm,50 with the realization of the importance of self- organizational phenomena as a generator of emergent order beyond the genes, i.e., non-Darwinian “order for free.”51 [50. Charles David Allis, Thomas Jenuwein, Danny Reinberg, and Marie-Laure Caparros, Epigenetics (Cold Spring Harbor, NY: Cold Spring Laboratory Press, 2007); Pigliucci and Müller, op. cit., Chapter 7; Eva Jablonka and Marion J. Lamb, “Transgenerational Epi-genetic Inheritance,” in Evolution–the Extended Synthesis, and Chapter 12; Gerd Müller, “Epigenetic Innovation.” 51. Stuart A. Kauffman, The Origins of Order: Self-Organization and Selection in Evolution (New York: Oxford University Press, 1993) Note that Turing, as long ago as 1952, proposed a self-organizing mechanism capable of generating organic patterns; see Alan Turing, “The chemical basis of ]4[ morphogenesis,” Philosophical Transactions of the Royal Society of London, Series B, Biological Sciences 237, no. 641 (August 14, 1952): 37–72.] [Michael Denton: Evolution, Still a Theory in Crisis (Kindle Locations 330- 335). Discovery Institute Press. Kindle Edition.] Richard Prum and Alan Brush, the researchers who elucidated the development of the feather, speak for many workers in the evo-devo field when they write: Recently, Wagner and colleagues... proposed that research on the origin of evolutionary novelties should be distinct from research on standard microevolutionary change, and should be restructured to ask fundamentally different questions that focus directly on the mechanisms of the origin of qualitative innovations. This view underscores why the traditional neo-Darwinian approaches to the origin of feathers, as exemplified by Bock (1965) and Feduccia (1985, 1993, 1999), have failed. By emphasizing the reconstruction of a series of functionally and microevolutionarily plausible intermediate transitional states, neo-Darwinian approaches to the origin of feathers have failed to appropriately recognize the novel features of feather development and morphology, and have thus failed to adequately explain their origins. This failure reveals an inherent weakness of neo-Darwinian attempts to synthesize micro and macroevolution. In contrast, the developmental theory of the origin of feathers focuses directly on the explanation of the actual developmental novelties involved in the origin and diversification of feathers (Prum 1999). Restructuring the inquiry to focus directly on the explanation of the origin of the evolutionary novelties of feathers yields a conceptually more appropriate and productive approach.53 [53. Richard O. Prum and Alan H. Brush, “The Evolutionary Origin and Diversification of Feathers,” Quarterly Review of Biology 77, no. 3 (September 2002), 261-295, 289, emphasis added. For references cited in the passage, see the original article.] [Michael Denton: Evolution, Still a Theory in Crisis (Kindle Locations 346-357). Discovery Institute Press. Kindle Edition.] In the same vein, Douglas Erwin entitled one of his papers “Macro-evolution Is More than Repeated Rounds of Microevolution”;54 and in another paper, Erwin and colleague Eric Davidson argued that micro-evolutionary changes are not able to account for the origins of or