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9/27/2012 History of Evolutionary Thought Epistemology and Evolution • Argument from Authority – Reality can be explained by scripture or by persons • Methodological Naturalism – Nature to explain nature – Supernatural explanations are not allowed Rise and Fall: in a nutshell • Greeks used methodological naturalism • After, Aristotle and scripture used for knowledge • Methodological naturalism rejected – not entirely • 18th century: Age of Enlightenment Aristotle (384-322 B.C.E.) Plato’s student Studied ecology, biology, and geology Continued Plato’s idea of eidos Concept of eidos for species persisted until Darwin – Search for laws Age of the Earth • Greeks: eternal • Bible scholars: ~ 5000 years • George Buffon (1707 – 1788), French naturalist – 75K to 2-3M years – Used observations • James Hutton (1726-1797), Scottish geologist Charles Lyell (1797-1875) • Principles of Geology (1830) • Based on uniformitarianism • Was the geology textbook of Darwin’s day • Friend of Darwin – Founder of modern geology – Earth is incredibly old – Uniformitarianism 1 9/27/2012 Natural History and Classification • Aristotle proposed a simple classification with genus and species • Scala naturae: Great Chain of Being • Karl von Linne (Carl Linnaeus, 1707-1778) – Binomial nomenclature – Systema naturae – Was all about sex! Organisms and their environment • William Paley (1743-1805) Natural Theology – God as Watchmaker • Extinctions are impossible – Lewis and Clark • Georges Cuvier (1769-1832), French – Father of paleontology – Extinctions are real Change through time • Greeks proposed it • Bible scholars forbid it – Organisms created perfectly – Immutability of species • Erasmus Darwin (1731 – 1802) – Charles Darwin’s grandfather – Zoonomia (poem) – Organisms evolve in scala naturae – Publically ridiculed Change through time Change through time • Robert Chambers – Vestiges of the Natural History of Creation (1845) – Organisms evolve – Process is slow – Emphasis on populations • Jean-Bapiste Lamarck (1744-1829) – Zoological Philosophy (1809) – Inheritance of acquired characteristics Along came Darwin 1809—1882 • Grandfather and father were doctors • Went to Edinburgh for two semesters to study medicine – dropped out • Went to Christ’s College to be a clergyman – – – – Studied natural theology: geology and natural history Energetic field student Urged to go aboard the HMS Beagle The captain (Robert FitzRoy) needed a companion of similar social stature 2 9/27/2012 Voyage of the HMS Beagle Voyage of the Beagle • Surveying trip – Map coastlines – Test new equipment • Naturalist on board was the doctor • Was supposed to be three year journey – went 5 • Left 1831, Darwin age 22 • Went to Azores, S. America, Galapagos, Australia, Tahiti Voyage of the HMS Beagle • • • • • Darwin collected fossils and living organisms Ship’s official naturalist left Darwin shipped materials back Became famous as a naturalist Wrote several books soon after Voyage of the HMS Beagle • Observations – Each Galapagos island had its own turtle, mockingbird – Fossil species similar but not the same as extant species – Similar species over land masses – Struggle for existence • Thomas Malthus Darwin, from boat to book • After the Beagle trip, married and settled in the country • Studied barnacles, worms, seeds • Researched like mad • Did not work for a living – Married cousin, invested, inheritance • Thought about natural selection and evolution • Thousands of letters of correspondance Alfred Russel Wallace (1823-1913) • Studied butterflies in southeast Asia • Knew many of the same facts as Darwin • Sent Darwin an outline of natural selection in 1855 • In 1858, co-authored a paper with Darwin on natural selection • Not a big hit 3 9/27/2012 Origin of Origin Natural selection sensu Darwin • Happens when • Inspired by Wallace, finally published his draft On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life in 1859 • Stressed the importance of variation within a species • Natural selection • Common ancestry: hierarchical branching – Taxonomy reflects ancestry Process related to artificial selection – More organisms are born than can survive and reproduce • Competition to represent the next generation – Those organisms more likely to survive because of some trait will leave more offspring – If that trait is heritable then the offspring will have that trait – If conditions continue then that trait will spread in the population Major Darwinian Ideas • Natural selection • Common ancestry Interspecific variation There are fitness consequences to this variation • Organisms vary within a species Male tail streamers length as a predictor of reproductive success: (a) First brood breeding success, (b) Annual breeding success, (c) Successful genetic offspring in first brood, and (d) Annual genetic breeding success. Vortman Y et al. Behavioral Ecology 2011;beheco.arr139 © The Author 2011. Published by Oxford University Press on behalf of the International Society for Behavioral Ecology. All rights reserved. For permissions, please e-mail: [email protected] 4 9/27/2012 The variation is heritable Natural selection occurs Dave Reznick Caribbean Anoles Common Ancestry • Phylogenetic trees Pre-Darwinian Linnean classification Species A Species D Species E Genus C Genus G Species B Species F Family H Post-Darwinian Classification Species A Species B Species D Common Ancestor C Species E Species F Common Ancestor G Common Ancestor H 5 9/27/2012 Phylogenetics and Taxonomy • Pre-Darwinian Taxonomy –Classification arbitrary Reception of Origin • Most scientist accepted evolution • Natural selection not as widely accepted • Post-Darwinian Taxonomy –Classification represents lineages –Taxon = monophyletic group • Taxonomy should reflect phylogeny Issues with Darwin • Eusocial insects • Mechanism of heredity unknown • Time To recap • Darwin’s contributions – Evidence that evolution happened – Mechanism of evolution: natural selection – Pattern of evolution: heirarchical Rise of the Geneticists • Weisman's germplasm hypotheses – Contra Lamarck • Hugo DeVries – worked with mutations – genes • Early Geneticists – Variation was discrete – Mutations produced large changes • Naturalists – Most variation was continuous 6 9/27/2012 Population Genetics • Resolved the dispute between naturalists and geneticists • Modern Synthesis of 1940’s – Ronald Fisher – Theodosius Dobzhansky – Sewall Wright – JBS Haldane – Ernst Mayr – George Simpson Population Genetics • Evolution is – Descent with modification – Change in gene frequency 7