Evolutionary Psychology

1. Evolutionary Psychology • Scientific study of human behaviour, brain, mind within an evolutionary context • Relatively new as actual academic discipline • Principles have been around for long time • Not a sub-discipline of psychology, but a general theoretical approach

2. Humans’ Place • Humans are animals • But are they special animals? • “Gradual” vs. “recent” development of modern human characteristics • Bias, agenda

3. Mammalian Social Organization • Milk production • Mother-offspring association • Matrilineal cross-generational bonds • Females are the limiting resource • Polygyny and monogamy

4. Milestones major advance in tool manufacture; the Mousterian (200k) agricultural revolution origin of modern humans in Africa (200k?) first cities (6k) Industrial Revolution (150) first evidence of art (70k) technological revolution (25) controlled use of fire (~800k) present evidence of meat eating becomes strong 0.01 million 0.1 million grinding wild grains for baking (25k) 1 million Major advance in tool manufacture; the Achulean Homo erectus expands out of Africa 2 million earliest-known stone tools, Africa origin of brain expansion earliest-known fossils (A. afarensis Homo sp.?) origin of bipedalism in Africa 3 million 4 million Adapted from: Leakey (1994) 5 million 10 million

5. Australopithecine ~ 3.5-2.7 myr Brain size: 650 cc Homo habilis ~2.4-1.7 myr Brain size: 800 cc Homo erectus ~1.7-0.3 myr Brain size: 900 cc Homo Neanderthalensis ~250-45 kyr Brain size: 1400cc Image sources:http://www.archaeologyinfo.com, http://paleodirect.com/, http://www.talkorigins.org/faqs/homs/eurydice.jpg

6. Broad “Assumptions” of EP • Brain is physical system • Psychological systems (neuronal, cognitive, behavioural) adaptively selected for problems faced by our ancestors in Environment of Evolutionary Adaptiveness • Selective pressures have produced cognitive modularity

7. Brain is a Physical System • Materialism • Brain is a physical organ • Activity of brain is “the mind” • Evolution typically used to study physical adaptation • But behaviours derived from brain, so evolution can be applied here, too

8. Adaptive Selection • Environment of Evolutionary Adaptiveness (EEA) • Period of evolutionary pressures on human ancestors prior to about 10000 years ago • Selected and shaped species-specific traits seen in modern humans • Because of changes in environment, some of these traits may no longer be well suited to the modern environment

9. Modularity • Fodor (1983), The Modularity of Mind • Small, independent, impenetrable units • Generally applied by EP not only to perceptual systems, but to cognitive and behavioural ones as well (more on this later…)

10. Levels of Causation • Proximate (or Mechanistic) • Developmental (or Ontogenetic) • Phylogenetic (or Historic) • Ultimate (or Functional)

11. Food sharing between family members • Breast feeding • Monogamy • Language • Sibling rivalry

12. Levels of Causation • Different areas of science operate at different levels • Very different explanations may all be correct, just at different causative levels • Even sub-disciplines of psychology operate at different levels • Depending on the topic of focus, EP may also be operating at different levels

13. History of Evolutionary Theory • Did not start with Charles Darwin • All evolutionary theories address: “how do organisms change with time?” and “how do new organisms develop?” • Greeks • Thales and Empedocles: change across generations • Aristotle: strict, rigid hierarchy

14. Francis Bacon (1561-1626) • Novum organum (1620); variation across generations • Gottried Leibniz (1646-1716) • Ammonites & nautilus; environment causes change • George Leclerc, Comte de Buffon (1707-1788) • Adaptation to fit environment • e.g., N.Am bison from ox • Immanuel Kant (1724-1804) • Apes could develop the abilities of reasoning beings

15. Erasmus Darwin (1731-1802) • Single source of beginning of life • Competition as driving force of evolution • Sexual reproduction, The Botanic Garden • Baron Georges Cuvier (1769-1832) • Catastrophism: periodic extinction of species

16. Jean-Baptiste Lamarck • Gives mechanism for evolutionary change • Movement towards higher forms • Individuals change during lifespan • Inheritance of acquired characteristics (i.e., changes passed to offspring)

17. Charles Darwin • Lots of geology and entomology • Voyage of the Beagle (1831-1836) • Existence of adaptations • Read Malthus’ Essay on the Principle of Population • Not everyone can survive

18. Darwinian/Natural Selection • 1837: started notebook on “transformation of species” • On the Origin of Species (1859) • Variation, inheritance, selection • Provided causal mechanism • Selection • Artificial, natural, sexual • Not intentional, gradual, differential reproductive success Alfred Wallace

19. Requirements of Evolution • Heritable variation • Differential reproductive success

20. Gregor Mendel • “Founder” of modern genetics • Experiments with pea plants (also fuschia, maise, etc.) • Particulate inheritance • “Gene” • Darwin didn’t know anything about this…

21. Social Darwinism • Herbert Spencer (1820-1903) • Applied evolution to everything • Animals, human mind, society • “Survival of the fittest” • Directed, purposeful

22. Helping the weak limits society • Government should not be involved in social programs • Appreciated by 19th C. American industrialists • e.g., “The growth of a large business is merely survival of the fittest…” (J.D. Rockefeller) • e.g., “All is well since all grows better.” (A. Carnegie)

23. Francis Galton • Charles Darwin’s cousin • Developer of modern field of psychometrics • Early use of twin studies to understand heritability of intelligence (Hereditary Genius) • Argued traits from EEA useful in modern period (e.g., social nature, gregariousness) • Eugenics movement

24. Eugenics • Improve society by selective breeding • Not a new idea, e.g., Greek city state Sparta • Herbert Spencer • Hitler • Alberta Eugenics Board • Environment changes; necessary to predict future…

25. Evolved Instincts • William James • Humans possess inherited, evolved instincts • But environment and learning can modify many “instinctive” behaviours • Now, better to say “biological predispositions”

26. Standard Social Science Model (SSSM) • Nature vs. Nurture issue • Shift to importance of environmental factors in behavioural regulation • Early Behaviorists, developmental and social psychology • Tabula rasa, total modifiability, culture as autonomous force, behaviour via general learning rules

27. Nature via Nurture • Much of psychology studied at proximate level of causation • Genetic and Environmental interaction is a constant

28. Sociobiology • E.O. Wilson • Behaviours affect reproductive success, and behaviours influenced by genes • Ergo, evolutionary selection has helped shape human behaviour • Fears of a new social Darwinism

29. Risks for EP • Teleological assumptions; evolution has no “end-goal” • Assuming all modern traits must be derived from selected-for adaptations • Arguing without sufficient evidence (“just-so stories”)

30. Solutions • Study gene-environment-behaviour interactions • Behavioural genetics (won’t indicate if a trait is an adaptation, though) • Comparative approach • Cross-species comparisons • Cross-cultural approach • Behavioural “universals” across time and space; complicated due to environmental contingencies • Mathematical and computational modeling • Genetic algorithms, game theory, neural networks

31. Misconceptions about EP • A variety of misunderstandings • Many derive from a broader misinterpretation of general evolutionary theory

32. Everything is an Adaptation • Not all present traits must have been adaptively selected • Spandrel • Non-adaptive trait as side-effect of an adaptive one • Exaptation • Trait shaped by evolution for a specific purpose that is subsequently coopted for a new use • Sensory bias • Trait as side-effect of sensory/perceptual system

33. EP is Deterministic • “Genetic determinism” • Remember, genetics interacts with environment • Actually, relatively low heritability of many behavioural traits • Effects of learning very significant • E.g., Abbey (1982), Buss (1994): woman smiles, man misinterprets

34. EP is Reductionistic • Reductionism: taking something down to its most constituent parts • Sometimes rather absurd • Levels of causation • Certain degree of reductionism very useful in science

35. EP Argues for Optimal Design • No organism is fully optimized • Evolution: “good enough” to last long enough to reproduce • Evolutionary time-lag • E.g., clogged arteries and heart attacks • Costs of adaptation • E.g., fear of snakes and spiders, not cars

36. EP is Politically Incorrect • Science • Social-cultural elements

37. Field in Progress • EP is a developing field • Disagreement over underlying theory

38. EP, Santa Barbara Style • Late 1980s - early 1990s, Leda Cosmides & John Tooby • University of California, Santa Barbara • Center for Evolutionary Psychology • Formalized the developing field of EP • Adapted Mind (1992) • Universal human trait adaptations • EEA; slow evolutionary development • Cognitive modules • Currently, most well-known and popular(ized)

39. Universal Traits • Politically correct • Specter of sociobiology • Avoids claims of racism • Cognitive psychology • Specific link between cognition and genes not well understood • Physiology and (some) gene interactions better understood • Therefore, look for pan-human attributes

40. Slow Evolution • Older biology, evolution, genetics operated on assumption of slow evolutionary change • Made Pleistocene mind in modern body assumption reasonable • Modern research challenging this

41. Hawks et al. (2007) • Linkage disequilibrium study of the HapMap genotype data set • Recent selection (within last 10,000 years) on 1800 human genes • Ascertained selected variants • About 7% of human genes • Indicates that human evolution has actually increased over last 50,000 years • Population increase, cultural development, ecological modification

42. Wang et al. (2006) • Identified biological functional categories for recently (less than 40,000 years) selected human gene function • Non-random (indicating specific human relevant selection pressures) • Pathogen-host interaction, reproduction, DNA metabolism, cell cycle, protein metabolism, and neuronal function • Neuron function includes genes for: • Serotonin transporter, glutamate and glycine receptors, olfactory receptors, synapse-associated proteins, and numerous brain-expressed genes with largely, as yet, unknown function

43. Cognitive Modules • Idea that specific brain “units” have evolved for specific, ancestral tasks • Little/no change from ancestral form • Each module for single function • Cognitive science argues for brain as general pattern classifier • More on this later in course…

44. Popularized • Evolutionary psychology; catchy name • Santa Barbara school the early adopter • Numerous popular-press books

45. Caveat • Issues with some underlying assumptions do not invalidate value of applying evolutionary theory to psychological topics! • Scientists (in any field) frequently debate assumptions, findings, and interpretations • Other evolutionary approaches

46. Human Behavioural Ecology (HBE) • Applies principles of evolutionary theory and optimization to human behavioural and cultural diversity • Early roots in ethology and sociobiology • Modern HBE studies evolution and adaptive design in ecological context

47. Dual Inheritance Theory (DIT) • Culture and genes provide separate, but linked, systems of inheritance and variation • Cultural information affected by natural selection, decision making (genetic and/or culturally evolved preferences) and transmitter influence • Often utilize explicit mathematical models

48. Summary Comparison From: Winterhalder & Smith (2000)

49. EP, HBE, DIT • Traditionally viewed as competing fields • Different assumptions, analytic methods, alliances with other disciplines, academic politics • Increasing recognition of complementary integration • Take advantage of different study methodologies, empirical foci, time scales of adaptation, behavioural domains • Limits to complementarity • The same behaviour can’t simultaneously be the product of each field’s underlying assumptions • But, different these field’s hypotheses could be simultaneously true for different behaviours