Unformatted text preview: 9/1/2010 IB35 Human Biological Variation Class #3 William Paley Natural Theology (1802) “the blind watchmaker” analogy Topics for today:
Darwin and Evolutionary Theory Phylogenetics Charles Darwin
The essence of a scientific proposition is that is can be tested by observation tested by observation.
1809 – 1882 Voyage of the Beagle
18311831-1836 • 1797 – 1875 • Principles of Geology • (elaborated on Hutton’s uniformitarianism) Charles Lyell 1 9/1/2010 Georges Cuvier
• French anatomist • 1769 – 1832 • catastrophism Darwin’s most important observations on his trip:
• Succession of fossil animals in South America • Geographical variation in species variation in species • Ocean island species (i.e., the Galapagos) Darwin observed that:
1 – organisms tend to produce more offspring than needed to keep the population size stable. 2 – population size stays stable. What does this mean? Conclusion: More of Darwin’s observations:
3 – Variation is an innate characteristic of life: individuals vary. 4 – Offspring tend to look like their parents (kids inherit this variation). There There is a lot of death. What does this mean? 2 9/1/2010 Conclusion: Survival of the fittest. th fitt Darwin said that the natural variation in the population was selected on by the environment to cause cause evolution. Fitness: reproductive success Change Change over time is caused by differential reproductive success differential reproductive success. Individual Fitness: success in Fit promoting survival of one’s own genes; measured relative to other individuals Strategies for increasing fitness: IMPORTANT POINT: Reproductive success is NOT how many times you mate!
Frogs: maximize production of offspring Monkeys: maximize care of just a few offspring 3 9/1/2010 Alfred Russell Wallace
1823 -- 1913 On On the Origin of Species
Charles Darwin 1859 Darwin’s three main contributions:
• Collected evidence to document the occurrence of evolution • Provided a natural mechanism for evolution (that natural selection is the creative force behind evolution) evolution) • Established a methodology and developed criteria for inferring the processes we cannot see from the results that have been preserved Before Darwin:
• Species arose through a special creation and had not changed since • The Earth is not very old (John Lightfoot estimated estimated it’s creation at 9am on 23 Oct 4004 BC) • Linneaus and Cuvier • Lamark and Hutton And then there was Charles Darwin…
• • • • • And Lyell… And Malthus… And the voyage on the Beagle… the voyage on the Beagle And Alfred Russell Wallace… On the Origin of Species (1859) Evolution by Natural Selection in three parts:
1. The principle of variation There is variation in morphological, physiological, and behavioral traits among members of a species. 4 9/1/2010 Evolution by Natural Selection in three parts:
2. The principle of heredity Th The variation is in part heritable, so individuals resemble their relatives more than they resemble unrelated individuals, and, in particular, offspring resemble their parents. Evolution by Natural Selection in three parts:
3. The principle of differential fitness Different variants leave different numbers Different variants leave different numbers of of offspring either in immediate or in remote generations. The Science of Who’s Related to Who
• Phylogenetics – the science of describing the relationships between organisms and the processes behind these relationships • Taxonomy – the science of naming and formally classifying groups of organisms • Evolutionary lineages How do you do comparative analyses?
• Look to see how things differ
– How do you “see” differences? do you see differences? • Look to see how things are the same
– How do you “see” sameness? Ways to Make Phylogenetic Trees
• Assessing overall similarity • Cladistics (phylogenetic systematics)
– Willi Hennig (1956, 1966) – Incorporates actual evolutionary relationships – Derived versus primitive characters 2 Types of Shared Characters:
• Primitive • Derived 5 9/1/2010 We build phylogenies based on comparisons of:
Genus: Felis Genus: Papio Genus: Pan Genus: Homo cats baboon chimpanzees & bonobos humans • Gross anatomy • Molecules • Fossils Homology:
Similarity due to descent from a common ancestor (indicates evolutionary relationship) Analogy:
Similarity due to independent evolution for a common function in separate groups
(This is also called convergent evolution.) (Can also be called parallel evolution if the organisms are pretty closely related.) Icthyosaur Porpoise Mice An example of parallel evolution… Tiger shark Aye-aye 6 9/1/2010 The Controversy of Evolution
• Before Darwin
– variation is just “noise” – Teleology (order is inherent) – A static world static world Jean-Baptiste Lamarck
• 1744-1829 • French anatomist • Mechanism of evolution: inheritance of acquired characteristis (use and disuse of body parts) • Progressive evolution • Hereditary plasticity • Jean Baptiste de Lamarck
– Transmutation – Teleological Teleology
• “A teleological explanation is one that explains the existence of occurrence of something by citing a goal or purpose that is served by the thing is served by the thing…”
• (from Daniel Dennett’s 1995 Darwin’s Dangerous Idea, p.24) Evolution by Natural Selection
• Transmutation/evolution was not new • Theory of evolution BY NATURAL SELECTION was new • Selection by the environment brings order out of randomness (accumulation of design) • Natural selection answers the “why” question of evolution • Another important point: The individual is the most important unit of biological change • Another important point: Variation among individuals is essential What Darwin Actually Said
• Proposed a testable hypothesis
– Darwin writes 14 chapters trying to demonstrate that evolution by natural selection didn’t happen, but comes to the pp conclusion that all the data he compiled can’t refute this idea. Prelude to the Scopes Trial
• Summer for the Gods, by Edward J. Larson • March 1925, Tennessee’s Butler Act is passed • ACLU offered to defend anyone willing to teach evolution in defiance of this law evolution in defiance of this law • City of Dayton (pop. 1,756), looking for publicity • John Scopes indicted in April of 1925 7 9/1/2010 The Scopes Trial
• Prosecution brings in William Jennings Bryan • Defense then brings in Clarence Darrow Bryan’s view on evolution
• Darwinism undermined morality • Vernon Kellogg, 1917, Headquarters Nights: A Record of Conversations and Experiences at the Headquarters of the German Army in at the Headquarters of the German Army in Belgium and France • Benjamin Kidd, 1918, The Science of Power • James Leuba, 1916, The Belief in God and Immortality Herbert Spencer
• 1864 Principles of Biology
– Coined “survival of the fittest the fittest” Is this Evolution by Natural Selection?
If Nature does not wish that weaker individuals should mate with the stronger, she wishes even less that a superior race should intermingle with an inferior one; because in such a case all her efforts, throughout hundreds of thousands of years, to establish an evolutionary higher stage of being, may thus be rendered futile.
– Adolph Hitler, Mein Kamph • But he really applied a Lamarckian sense of evolution to sociology rather than natural selection The “Moral” Problem Posed by Darwin
• Evolution by natural selection provides no clues for human conduct or moral dilemmas • People find comfort in order and purpose Does Evolution Make us Immoral?
"… the ethical progress of society depends, not on imitating [nature], still less in running away from it, but in combating it."
– T. H. Huxley 8 ...
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