History of Evolutionary Thought Diane Philip

I. What is Evolution? Evolution: a gradual process by which the living world has been developing following the origin of life.

II. 18th and 19th centuries Species were thought to have a fixed form. Species defined mostly by their morphology (appearance). World was believed to be perfectly designed and earth was very young.

II. 18th and 19th centuries Classification system based on assumption that species were static (unchanging). Carl Linnaeus (1708-1788) created hierarchical classification scheme with binomial naming (genus species). Classification used as a method of organizing, not a way to show relationships.

III. Early Ideas of Evolution George Louis Leclerc (1707-1778): French naturalist who first suggested evolution. George Cuvier (1769-1832): Vertebrate zoologist who suggested Catastrophism (Mass extinction). James Hutton (1726- 1797): Proposed the Uniformatarian Theory of geology. Theory states that geologic processes happen at the same rate today that they have throughout the earth’s history.

III. Early Ideas of Evolution Jean Baptiste Lamarck (1744-1829): French naturalist and taxonomist. He proposed the Theory of Acquired Characteristics.

IV. Enter Darwin (1809-1882) Early Life: Charles Darwin (1809–1882) was born at Shrewsbury in northwestern England. He was sent to Edinburgh University at age 16 to study medicine. In 1827 he was sent to Cambridge University to become an Anglican clergyman.

IV. Enter Darwin (1809-1882) Voyage of the H.M.S Beagle: Asked by Capt. Robert FitzRoy on a voyage to chart South America coast in 1831. Read Principles of Geology by Charles Lyell, which discussed theory of uniformitarianism. Wanted to extend it to all animals. Noticed “family resemblance” between species (living and fossil) in areas he studied.

IV. Enter Darwin (1809-1882) Galapagos Observations different islands, climates, vegetation differences in animals (tortoise & finch) could these differences be the result of the differences among islands? could each animal have come from a common ancestor?

IV. Enter Darwin (1809-1882) Development of Natural Selection Malthus said as the human population outgrows it’s resources, members must compete for what is available. Darwin thought the same principle might apply in nature. Individuals with favorable traits might have an advantage in survival and reproduction. Favored individuals would pass their traits on to their offspring.

IV. Enter Darwin (1809-1882) Darwin and Alfred Russel Wallace’s papers were presented as a scientific meeting in 1858 but received little fan fare. Darwin’s findings were published in a book “On the Origin of Species” in 1859.

V. Neo-Darwinian Synthesis After about 1870, scientific evidence piled up against natural selection: The Earth was too young. Apparent ‘swamping’ of favorable variations. Lack of transitional forms in the fossil record. Biologists convinced that evolution had occurred but no longer saw natural selection as its chief mechanism The main scientific objections to Darwinian natural selection theory were answered by the 1930s: Discovery of radioactivity and later studies of decay rates showed age of earth to be 4 billion years. Swamping inheritance problem and lack of transitional forms in fossil record both resolved by Mendelian genetics.