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Simplifying Complexity – Evolution and Biological Complexity Timothy Bonebrake – November 5, 2014 I. Important figures and events in the development of evolutionary theory 1. Darwinism a. William Paley (1743-­‐1805) – Natural History: or, Evidences… of the Deity…, Darwin favorite, watchmaker analogy b. Jean-­‐Baptiste Lamarck (1744-­‐1809) – Philosophie Zoologique, transformation via internal force, use/ disuse, species not fixed. c. Thomas Malthus (1766-­‐1834) – An essay on the Principle of Population, food supply (arithmetic) vs. pop demand (exponential) d. Charles Darwin (1809-­‐1882) – On the Origin of Species, evolution by natural selection, influenced by Smith, Malthus and Paley. e. Alfred Russel Wallace (1823-­‐1913) – natural selection, biogeography. 2. The Modern Synthesis a. R.A. Fisher (1890-­‐1962), J.B.S. Haldane (1892-­‐1964), Sewall Wright (1889-­‐1988) showed how natural selection could operate under Mendelian genetics. b. History of eugenics (especially Fisher and Galton) c. Genetic drift vs. selection d. Theodosius Dobzhansky (1900-­‐1975) – studied populations of flies. e. E.B. Ford (1901-­‐1988) – studied natural populations (Ecological Genetics), e.g. peppered moth. f. Ernst Mayr (1904-­‐2005) – biological species concept. 3. The structure of evolutionary biology today involves systematics, genetics, physiology, developmental biology, ecology etc. 4. Evolution is important for our daily lives. In medicine for example, it is critical in understanding where SARS came from and how to treat HIV. II. Of watches and watchmakers 1. Richard Dawkins wrote The Blind Watchmaker as response to Paley to “prove” the non-­‐existence of God. 2. Recent trends have seen Intelligent Design (ID) replace Creationism 3. Irreducible Complexity is central argument in ID: that the whole cannot function without all of the component parts, i.e. “too complex”. 4. There are many problems with ID arguments scientifically a. Reductionism taken to an extreme b. Plenty of things appear complex and have been designed but are not (recall many examples throughout the course) c. We know how eyes have evolved (not through ID) 5. Evolutionary biologists have a huge range of personal beliefs from vehemently atheist (Dawkins) to very religious (Joan Roughgarden) but these personal beliefs are distinct from evolutionary science. III. Burgess Shale and the “nature of history” 1. SJ Gould wrote Wonderful Life based on findings from the Burgess Shale. 2. Earth’s history: 4.5 billion yrs old, Cambrian explosion occurred 500 mya when lots of animal body plans emerged. 3. Most animal phyla emerged during the Cambrian 4. Lots of fossils unearthed in the Burgess Shale exemplify Earth’s wondrous biological history including Nectocaris, Odontogriphus, Hallucigenia, Opabinia 5. Pikaia represents one of the early chordates (us!) 6. The “march of progress” represents a familiar but false evolutionary icon 7. The “increasing cone of diversity” also frequently hides the complicated evolutionary histories experienced by lineages. 8. In “replaying life’s tape” we get an intuition for the rarely (arguably) directional nature of evolution. The Burgess Shale shows nicely how small changes in the results could have altered life’s history. VI. Genetics, simplified 1. Life is made of cells. In cells there are nuclei. In the nucleus there are chromosomes which contain DNA (and other things). 2. Watson and Crick (with help from Franklin) discovered the structure of DNA. 3. Transcription: DNA is unwound and mRNA is transferred out of the nucleus. 4. Translation: Ribosome produces polypeptide chains via mRNA pairings with amino acid-­‐attached tRNAs. 5. Codons (three nucleotides) are the basis of the “genetic code”. VI. Major evolutionary transitions 1. Gene number generally increases with complexity… but not always as you might expect (more genes in grapes than humans). 2. The history of life can be thought of as a series of evolutionary transitions a. RNA world – RNA was the main replicator of life. b. Eukaryote – Increased cellular structure (and size) via cytosis. c. Sex – Genetic exchange allows faster evolution. d. Evolution of multicellularity i. Has evolved independently many times in life’s history ii. Cambrian explosion was a hotbed for this activity e. Eusociality – Organization of animal societies and division of labor f. Human society – A number of features distinguish human society. i. Language and cultural information ii. Memes and horizontal transmission 3. Overall lesson here: evolution and the history of life is pretty freaking of awesome! Complexity has been an integral concept all along.