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Psychology 3229A/B
Scott Mac Dougall- Shackleton

Evolution & Human Behaviour Study Notes Lecture 1 Fluctuating asymmetry Fl.A = deviations from perfect symmetry in normally symmetric species Caused by environmental stress (i.e. poor nutrition) during development Refers to anatomy, not physiology Most attractive dancers were also most symmetric Symmetric men also have more sexual partners, begin intercourse earlier in life, and have more extramarital affairs Facial symmetry. . . Correlated to measures of health Predicts perceived attractiveness by others Facial attractiveness & sex hormones Attractiveness ratings taken with & without makeup; urine collected for hormone analysis High oestrogen (in urine) associated with. . . Higher attractiveness ratings Higher femininity Health Makeup eliminated all effects Cheater detection Logical problems involving cheater detection rather than rule verification are easier to solve Cross-culturally universal Evolutionary psychology & the SSSM SSSM (Standard Social Science Model) drove psychological research for decades; predicated on 3 assumptions: 1. Tabula rasa (blank slate) 2. General laws of learning 3. Irrelevance of biology Critiques of the SSSM (Tooby & Cosmides): 1. Misunderstands nature of development Genes can only act through environmental influences Species have predispositions for traits, not destinies 2. Creates a false dichotomy (i.e. nature vs. nurture) Example: melanin production & UV B o Genetic effects: different cultures have different levels of expression o Environmental effects: production depends on recent exposure to UV B o Trade-off between skin cancer prevention & vitamin D synthesis 3. Learning not governed by general laws (modular view instead) 4. Divides social & natural sciences Psychological phenomena arent separate from biology 5. Doesnt explain design (i.e. constrained to proximate vs. ultimate explanations of behaviour) Levels of analysis Mayr proximate & ultimate explanations Tinbergen 4 questions How does it develop? (ontogeny) What are the causal mechanisms? (physiological) How did it evolve? (phylogeny) What is the adaptive function? Cruel step-parent effect can be approached using LOAs Reduced parental investment in non-genetic offspring Socioeconomic status Increased stress Increased financial hardship in mixed families Human universals Denied by cultural relativists More potential cultures that have never existed than actual cultures that have Cultures are much more similar to each other than they are different. . . Social Verbal & nonverbal communication Exchange gifts Show hospitality Celebrations Punish theft, rape & murder Live in family groups; track marriages; track kin relations Sex differences in childcare & aggression Modest about sex & bodily functions Supernatural beliefs Common fallacies Deterministic/genetic fallacy Belief that what is encoded in genes is destiny/cannot be changed But many traits are flexible & respond to environmental influences (i.e. PKU, IQ, etc.) Opposite is cultural determinism Naturalistic fallacy Belief that what is natural is inherently right/good But adaptations are independent of morality Lecture 2 History of evolutionary thought Evolution: change in allele frequency over time Process, distinct from the mechanisms that cause it History started about 150 years ago Thales Explained origin of life in natural terms (first to do so) All life evolved from simpler elements, the simplest being water Empedocles 4 elements made up the earth Change arises through mixture of these elements (most combinations are deleterious, but some are beneficial) Plato Variation reflects deviations from ideal phenotype (i.e. two worlds, a perfect & an imperfect one) Aristotle Great Chain of Being (scala naturae) Species couldnt move between levels A fallacy because evolution is cumulative, NOT progressive Linnaeus Father of taxonomy; believed taxonomies reveal the plan of Gods creation Georges Cuvier Palaeontologist; hypothesized catastrophism (i.e. local catastrophes cause local extinctions) Taxa replaced by immigration Immanuel Kant Defied Aristotles scala naturae Hypothesized that anatomical structures could change to respond to various conditions Erasmus Darwin Grandfather of Charles Darwin Proposed impermanence of species; believed that competition drove change Jean-Baptiste Lamarck Inheritance of acquired characteristics (i.e. long necks in giraffes) Thought species could be transformed Charles Darwin Circumnavigated the globe in the Beagle (collected fossils in Andes; studied finches on Galapagos Islands) Proposed theory of natural & sexual selection, but was hesitant to publish Focus was on intraspecies competition Alfred Russell Wallace Believed discontinuity of species was due to plate tectonics Independently proposed natural selection Focus was on interspecies competition Evolution: the modern synthesis Natural selection: traits that increase reproductive success will be more likely to appear in subsequent generations (i.e. black peppers moths pre- & post-Industrial Revolution in Britain) Measured through long-term field studies 3 conditions 1. Variation among individuals 2. Much of this variation is inherited 3. More individuals are produced than can survive Evidence Fossil record Homologies Universal genetic code Artificial selection Direct observation Adaptive radiation: one common ancestor produces many similar species (i.e. Darwins finches) Measured through comparative analyses Types of evolutionary change Directional: mean for a trait shifts in one direction Stabilizing: extremes die off; becomes more concentrated around mean Disruptive: opposite of stabilizing (i.e. being average = bad) Genetic drift: change due to chance differences in genetic makeup Mutation Genetic variation is decreased by (a) natural selection, and (b) drift, but is increased by (c) mutation, and (d) sexual recombination Adaptation Adaptation: product of natural selection that increases reproductive success of the individual Distinguishes selection from drift Complex adaptations: collection of individual adaptations caused by cumulative selection (i.e. the human eye) Not all traits have been optimized View that all traits are adaptations is called panadaptationism/Panglossian approach Some traits are neutral, which can be maintained by (a) pleitropy, (b) linkage, and (c) immigration, and traits take time to go extinct Local adaptive peaks Problems with evolutionary theory Ant (why help others reproduce?) A case of direct versus indirect selection Peacock (why maintain elaborate costly traits that reduce survival?) Adaptations increase probability of genes being passed on, not necessarily survival Tail is a courting mechanism Behaviour genetics Studied using. . . Inbreeding Artificial selection Hybridization Mutation & screening studies Genetic engineering Single gene variations Variation at a single locus produces variation in behaviour Show Mendelian inheritance patterns (i.e. Punnett Square) Fearfulness in Basenji hounds Sickle-cell anemia Lactase production Tongue rolling Chromosomal variati
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