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Lecture 6

Lecture 6: Darwin and Evolution

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Natural Science
NATS 1760
Vera Pavri

NATS 1760- Darwin and Evolution • Darwin came up with a mechanism to understand the evolutionary process, the idea that things evolve through time is a debating topic that came about and does not belong to Darwin I. Intellectual and Scientific Background Prior to Darwin a. Great Chain of Being - Great Chain of Being: dominated religious thinking; fixity of species - God created all species according to certain order - Single hierarchy stretching from man to simplest form of life - Highest place on chain: God, angels, man - Hierarchy stable and harmonious but there is a problem: difficult to explain idea of extinction; if something is fixed how can it not exist, goes against notion of stability - To reconcile idea, had to image chain not as a stable representation (fixed) but as a sequence that would gradually change over long period of time - Dimension of time introduced b. Debates in Natural History and Classification * study each natural philosopher according to the questions - Debates center around following: how should things be classified (i.e. single or multiple characteristics); how much weight should be given to these characteristics; how much emphasis should be placed on how a living thing behaves, how it is constructed, or its natural environment; is behaviour important or is it the anatomy Carolus Linnaeus (1707-1778): publishes Systema Naturae in 1735 - Classified huge number of animals and plants: binomial nomenclature – How to classify living things? - Classified them according to seven groups (kingdom, class, order, genus, species, variety) - Belief that both plants and animals had been created in limited supply (fixed) by God; he focused on differentiating species based on their sexual/reproductive systems - Claimed there were essential characteristics of all living things but that they were difficult to identify Charles Buffon (1707-88): - Disagreed with Linnaeus and attacked hierarchal classification (emphasis of hierarchy) and too abstract systems - Wanted more “practical” method to organize species: look for patterns by observation, obtaining facts (application of Baconian ideals) - Bacons influence can be seen in Buffon, Inductive method - Believer in uniformitarianism (earth older than what was believed); publishes his book Natural History in 1749 - Up until this time age of earth was thought to be 6000 years, a sufficient amount of time for geological processes to take place - Claims age of earth much older - Wants to use present natural laws to explain past phenomena Jean Lamarck (1744-1829): early 19 century French naturalist - Advocated an evolutionary theory prior to Darwin - Believes in uniformitarianism (age is very old); fossils can aid in determining earth’s age - He had this idea that Simplest form of life (species) evolved from matter to more complex: spontaneous generation - Higher degree of organization equals higher degree of perfection - Species progress from lower to higher part of chain - Problem: how did evolution take place 1 - Had to be mechanism from which species adapt to changing environment - I.e. giraffe: neck originally small, but stretched it to get food from tree and eventually develops long neck - Used organs will evolve; disused or unused organs will degenerate - His theory is based on the idea of Inheritance of Acquired Characteristics: different from Darwin’s later theory - He was focused on species adapting to their environment - Environment shapes any given species, species not used become extinct (LOOK AT RECORDING) - Many of Lamarck’s ideas ignored; too vague - One individual that was especially against him was Cuvier who mobilized French biologists not to respond to Lamarck’s ideas E.g. Giraffe: First short necked creatures and eventually adapted to environment to look to for new resources, which required them to stretch their neck; reproduction of giraffes become long necked creatures Georges Cuvier (1769-1832) - French Philosopher, opposed Lamarck’s ideas - Interested in internal anatomy of invertebrates - His view looks for similarities in internal structure: comparative anatomy - Very interested in classifying species by function (i.e. flying, swimming) - Principle of correlation of parts: you should be able to tell properties of creature by just seeing one of its parts - Can thus rebuild and reconstruct animals - No belief in mingling of species, breeds do not mix together to create new species c. Geological Debates over Fossils - Discovery of fossils creates interest for naturalists - Problem of extinction: fossils of creatures like mammoths caused people to initially believe that these mammals were still living somewhere [how can this extinction occur if things are supposed to be “fixed”] - As fossils accumulate, fossils record points to fact that many mammals now extinct; problem is why mammals become extinct - Two explanations: uniformitarianism versus catastrophism Uniformitarianism - Long time span for formative process; geological mechanisms can help explain past events - Extinction takes place in a uniform way through an extensive period of time, gradually & slowly - God is a rational being, therefore likely to create a rational order world, and when accounting for change these kinds of changes would be done in a uniform and methodological way - Deists: Christians who believe God is rational; nature is ordered, rational - As such, should not have to invoke natural catastrophes to explain nature - Age of earth must be very old for these slow, gradual changes to occur - Evidence for older age of earth: lava found underneath volcano grounds - Depth and thickness of sedentary deposits in earth also suggest earth old - Australia: animals exist here that do not exist anywhere else - Differences found between existing animals were not as significant as differences between fossil animals Catastrophism: - Periodic di
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