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Chapter 17 Emergence of Evolutionary Thought

Chapter 17 Emergence of Evolutionary Thought - Chapter 17...

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Chapter 17 Emergence of Evolutionary Thought I. Fire, Brimstone, and Human History A. About 3,000 years ago, tremendous volcanic activity in the Mediterranean Sea area caused widespread destruction. B. Ignorant of the geologic forces responsible for these events, people in the region interpreted them as punishment. II. Growing Awareness of Change A. The Great Chain of Being 1. Many of the ancient Greeks, including Aristotle, attempted to explain the natural world by making direct observations. 2. By the fourteenth century, the ancient view of gradual levels of organization from lifeless matter to the most complex organisms had been formalized into the Great Chain of Being. a. The chain extended from lowest forms to spiritual beings. b. Each being (species) had its fixed place in the divine order—unchanged and unchanging since creation. B. Questions from Biogeography 1. When global voyages of the sixteenth century revealed unusual species not known in Europe, the students of biogeography began to question, “Where do all these species ‘fit’ in the Great Chain?” 2. Furthermore, if all species had been created at the same time and place, “Why were certain species found in only some parts of the world but not others?” C. Questions from Comparative Anatomy 1. Studies of comparative anatomy of seemingly unrelated animals led to questions of why certain structures should be so similar. 2. One explanation: Some body parts were so perfect at the time of creation there was no need for any variation; but what about bones still present but without function (pelvic girdle in snakes, tail bones in humans)? D. Questions About Fossils 1. Studies of stratification (layering of Earth’s rocks) revealed that deposits had been laid down slowly, one above the other. a. The layers held recognizable remains or impressions of organisms—fossils. b. The arrangement of the layers suggested that different organisms had lived at different times. 2. de Buffon’s explanation: Perhaps species originated in more than one place, and perhaps species became modified over time—evolution! III. Attempts to Reconcile the Evidence With Prevailing Beliefs A. Cuvier’s Theory of Catastrophism 1. Georges Cuvier believed in an original creation of all species. 2. Cuvier further suggested that the abrupt changes in the fossil record in different rock strata reflected the concept of catastrophism. a. After each catastrophe, fewer species remained. b. The survivors were not new species; it was just that their ancestors’ fossils had not been found. B. Lamarck’s Theory of Desired Evolution 1. Lamarck believed that simple forms had changed into more complex ones by a built-in drive for perfection up the Chain of Being.
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a. The drive was by “fluida” substances in the nerves.
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