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Discovering Evolution. 1 Lecture I. Introduction. Readings: Young, Ch. 1; Johnston. On the Importance of Darwin; As referenced in text. I. Introduction. A. Most scientists believe the question of evolution settled. 1. Significant segments of society nonetheless reject this conclusion – hence the “Evolution Wars.” 2. To characterize doubters / skeptics as “morons” unhelpful – see Bloom (2005). a. Poisons the well of civil discourse. b. Discourages objective consideration of what evolution can and cannot explain. 3. Stakes are enormous. a. Evolution arguably most important principle in biology. b. Humanity’s view of itself – “Why are we here?” – inextricably bound up with “How we came to be.” B. This class: We consider what the theory of evolution is and how it came to be. 1. The second question inevitably leads us to consider how science works. 2. We will also discuss the connection of scientific inquiry generally to broader societal issues. 2 II. The Wisdom of God Manifested in the Works of Creation. A. The Judeo-Christian tradition encouraged the study of the Nature as a way of studying God. “The concept of a created world gave grounds for regarding nature as orderly and open to rational inquiry. The study of nature could be acknowledged and respected as the study of God’s handiwork … .” – David Young. The Discovery of Evolution. B. The resulting studies led to replacement of Design by Descent with Modification. Compare 1. Paley’s “Teleological Argument.” (1800) vs. 2. Darwin-Wallace paper (1858). C. Eiseley (p. 198) argues that triumph of Darwinism does not rule out all forms of the design argument and is therefore compatible with certain kinds of religion. ”The evolutionists discovered that ‘nature makes things that make themselves’ and thus succeeded in apparently removing the need of a Master Craftsman. … it was only later that the question began to be asked: Why does nature let things make themselves? D. One answer is the Second Law of Thermodynamics: organized states of matter that don’t reproduce must eventually disappear. But that only begs the point. Why the Second Law? 3 III. Science as the Modeler’s Art. A. Models are simplified representations of reality. 1. Can be mathematical, pictorial or verbal. 2. Reduce real world complexity to “the essentials.” B. All theories are models, and they must be falsifiable. C. From mechanistic assumptions, one deduces predictions that can then be tested. Figure 1. Science as the modeler’s art. Mechanistic assumptions and simplifying approximations inform the construction of a model that generates predictions. Falsification results when observation contradicts prediction (red slashes) or when new observations indicate assumptions or simplifications to be untenable (blue slashes). D. Model falsification results if 1. Observation ≠ prediction. 2. Assumptions and / or simplifying approximations turn out to be wrong or inappropriate. E. Model acceptance results when repeated attempts at falsification fail. 4 F. Important: 1. A model can be falsified but never be proved. 2. .Revising a model in light of new information is not the same thing as confirming its predictions. 3. What results is a simply a new model, the predictions of which must then be subject to further experimental test. G. All models – even large scale simulations, e.g., climate models – reduce real-world complexity to a manageable approximation. 1. Simplification essential if models are to be useful – see Borges (1998). 2. “All-but-the-kitchen-sink” simulations replace systems that aren’t understood with models that can’t be understood – at least not mathematically. a. The best one can do is to perform (numerical) experiments. b. Over abundant computing power a temptation of modernity. 3. Real world complexity a source of confusion: Is predictionobservation conflict the result of a. Inappropriate mechanistic assumptions? b. Inappropriate simplifications? 5 H. Macroscopic vs. microscopic levels of organization. 1. Classic example is derivation of the gas law, PV = kT from a model of molecular collision. 2. Here, a. P, V, and T are macroscopic quantities. b. Molecular velocities are microscopic variables. Figure 2. Science at small and large length scales. A microscopic model generates macroscopic predictions. As in Figure 1, red and blue slashes indicate model falsification and need for revision. 3. In case of evolution, a. Gene frequencies are the microscopic variables; b. Their alteration by mutation, migration, selection, drift, etc., microscopic processes. c. History of life, patterns of diversity and phylogenetic branching, the macroscopic observables 6 Figure 3. Evolution according to the “modern synthesis.” IV. Two Theories of Evolution. A. Descent with modification (DwM) – the observable pattern; the processes that produce it – the responsible mechanisms. B. Regarding DwM: 1. Supporting evidence has been accumulating since before Darwin. 2. Seeking “God in the gaps” a fool’s errand. C. Regarding Mechanisms: 1. A succession of theories: Lamarck, Darwin-Wallace, Modern Synthesis, Post-Modern Synthesis. 2. Each informed by discoveries that invalidated previous assumptions and by independent opinion as to how the universe operates. D. No one has deduced the pattern from the mechanism. 1. In terms of Figures 1 and 2, we have never gone round the loop in the large. 2. With regard to the “Modern Synthesis,” recent advances in genetics and development suggest that we never could. 7 E. Contrasting Views: 1. “Nature, to cite a modern cliche, always bats last. She will not succumb to the simplicities of our hopes or mental foibles, but she remains eminently comprehensible. Evolution follows the syncopated drumbeats of complex and contingent histories, shaped by the vagaries and uniquenesses of time, place, and environment. Simple laws with predictable outcomes cannot fully describe the pageant and pathways of life.” – S. J. Gould (1999b). Problem: Post-facto comprehension ≠ à priori prediction. 2. “The primary problem with the synthesis is that its makers established natural selection as the director of adaptive evolution by eliminating competing explanations, not by providing evidence that natural selection among ‘random’ mutations could, or did, account for observed adaptation.” (Leigh, 1999). 3. “Microevolution, … while arguably consistent with larger scale patterns, does not predict them in detail. Variation plus selection does not, for example, predict that during the first 4 billion years of earth’s history, i.e., most of it, the dominant organisms were microbes. It does not predict the skeletization, if not the emergence, of the major taxonomic groups some half a billion years ago. Nor does it necessitate the dominance of early Paleozoic seas by invertebrates, nor the subsequent colonization of land by insects and the limbed descendants of rhipid8 istian lungfish. It cannot tell us that dinosaurs and mammals would come into being at about the same time, and, with regard to the 100 million year eclipse of the latter by the former, it says nothing. It is unable to tell us what would have transpired had the Chicxulub asteroid missed. And, of course, it cannot predict the emergence of man, much less the fact that humans would one day compose symphonies and argue as to whether or not God really does play dice with the universe.” F. When challenged, evolutionists are always more comfortable defending the pattern. 1. “Whether the naturalist believes in the views given by Lamarck, or Geoffroy St.-Hilaire, by the author of the 'Vestiges,' by Mr. Wallace and myself, or in any other such view, signifies extremely little in comparison with the admission that species have descended from other species and have not been created immutable; for he who admits this as a great truth has a wide field opened to him for further inquiry.” – Darwin (1863a). 2. “to learn that the same set of 25,000 to 30,000 genes is present in most animals. Almost every gene in our DNA has a homologous gene in the DNA of other mammals, such as the mouse. It is even more extraordinary when we look at more distantly related organisms; the invertebrate sea squirt, for example, has only half our number of genes, but as many as two-thirds of these have homologues in human DNA.” – J. D. Watson (2005). 9 3. “The evidence for common descent … is independent of specific gradualistic explanatory mechanisms. None of the dozens of predictions [discussed herein] directly address how macroevolution has occurred … . None … assumes that natural selection is valid [or] … that natural selection is sufficient for generating adaptations or the differences between species … . Because of this evidentiary independence, the validity of the macroevolutionary conclusion does not depend on whether natural selection, or the inheritance of acquired characters, or a force vitale, or something else is the true mechanism of adaptive evolutionary change. The scientific case for common descent stands, regardless.” – Theobald (2004). 10 Figure 6. Evolution of whales from artiodactyl-like ancestors. From “Walking with Whales.” 11 G. Darwin’s Facts. 1. “The view given by me on the origin or derivation of species … connects … by an intelligible thread of reasoning a multitude of facts.” a. “Formation of domestic races by man's selection,” b. “The classification and affinities of all organic beings,” c. “The innumerable gradations in structure and instincts,“ d. “The similarity of pattern in the hand, wing or paddle of animals of the same great class,” e. “The existence of organs become rudimentary by disuse,” f. “The similarity of an embryonic reptile, bird and mammal, with the retention of traces of an apparatus fitted for aquatic respiration;” g. “The retention in the young calf of incisor teeth in the upper jaw, &c.,” h. “The distribution of animals and plants, and their mutual affinities within the same region, – their general geological succession, and the close relationship of the fossils in closely consecutive formations and within the same country; extinct marsupials having preceded living marsupials 12 in Australia, and armadillo-like animals having preceded and generated armadilloes [sic] in South America,” i. “Many other phenomena, such as the gradual extinction of old forms and their gradual replacement by new forms better fitted for their new conditions in the struggle for life.” – Darwin (1863b) 2. Note that a. Only the first and last relate to selection. b. The last – gradual extinction and replacement – was and remains a pious hope. H. Some proposed evolutionary mechanisms have been, or at least are believed to have been, falsified. E.g., 1. Lamarck’s “Power of Life” – predicts massive parallelism – not observed. 2. Inheritance of acquired characters – segregation of germ cells and soma. In the process of resurrection by “transgenerational epigenetic effects?” 3. Orthogenesis and racial senescence – “bushiness” evolution / no known mechanism. 4. Result was the “Modern Synthesis.” 13 V. Plausibility and Expectations. A. Simplicity. Triumph of Darwinism was due principally to the fact that it offered a more economical explanation for emerging patterns of distribution and development, for the existence of homologous and vestigial organs, for adaptation and mal-adaptation, etc., than did the alternative theory of Special Creation. “… what would the Astronomer say to the doctrine that the planets moved [not] according to the law of gravitation, but from the Creator having willed each separate planet to move in its particular orbit?” – Darwin (1842). B. Mechanism. 1. Continental Drift proposed to explain geographical distribution of extinct species. 2. Initially rejected for lack of a plausible mechanism. 3. Discovery of sea-floor spreading proved Wegener had been right after all. Figure 4. Distribution of fossil Mesosaurus and other Permo-Triassic genera. The major landmasses are shown as they existed in relation to each other prior to the break-up of the super-continent of Pangea. The simplest explanation of such patterns is that the continents were assembled into a single landmass, as first proposed by Wegener [w15]. From http://de.wikipedia.org/wiki/Mesosaurier. 14 C. Experience. 1. Lyell correctly rejected Lamarck’s theory of spontaneous generation of unicells based on previous falsification of the hypothesis in case of lower plants and insects. 2. His belief that Paleozoic mammals and birds would eventually be discovered (i.e., as more fossil-bearing formations became available) proved wrong. D. World View. 1. Charles Lyell’s belief that earth’s history was entirely explicable in terms of “actual causes.” a. Accepted for over 100 years. b. Destroyed once and for all by discovery of iridium at Gubbio. 2. Lamarck’s belief that species evolved because Nature wouldn’t permit extinction. Figure 5. Iridium spike at Gubbio, Italy, provided 1st convincing support for termination of the Mesozoic by bolide impact. 15 3. Scientific worldviews can reflect both “known facts” and beliefs from outside of science. 1. Evolutionists like to point to the religious motivations of evolutionary skeptics. 2. But history teaches that there are other sources of ideological input. a. Lysenkoism. b. Eugenics 3. Science in the service of ideology usually results in bad science and bad policy. E. Facts Themselves Evolve. 1. Kelvin’s estimates (vs. Darwin’s assumed requirements) of the age of the earth suggest that when different intellectual starting points lead to vastly different conclusions, something undiscovered may be waiting in the wings. 2. The attempts of geologists to harmonize their estimates with Kelvin’s maximum grant of 100 m.y. also merits consideration – see Powell (2001; Chapter 1). a. “Facts” arrived at via the same iterative process of model formulation and testing described above. 16 VI. Wrap-Up. A. Evolution a central biological concept with implications that extend far beyond biology. B. Theory of evolution the unexpected consequence of trying to understand God’s Nature by studying His Creation. C. Theories are models that can be falsified but never proved. D. Some theories deduce macroscopic behavior from microscopic models. E. There are two theories of evolution. 1. Descent with modification – the pattern. 2. Mechanism that produces the pattern. F. Evidence for DwM overwhelming. G. Ideas as to mechanism continue to evolve. H. The evolution of scientific theories results from a complex interaction of theory and observation modulated by experience, philosophy and societal inputs. 17