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Chapter 2

PSY290- Biopsychology - Chapter 2

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University of Toronto St. George
John Yeomans

Chapter 2 : Evolution, genetics and experience • Zeitgeist ---> intellectual climate of our culture ---> bringing our understanding of biological bases of behaviour influenced by our Zeitgeist up to speed • Thinking about the biology of behaviour ◦ dichotomous reality of behaviour ▪ is it physiological or psychological? • Descartes ---> universe was composed of two elements ---> physical and the human mind ---> Cartesian dualism ◦ pleased the church ◦ some still believes that there is an aspect of the mind that transcends the brain • is it inherited or learned ? ◦ Nature-nurture issue ◦ ethology ---> instinctive behaviours ---> inherited factors ▪ assumed all behaviours were inherited ---> not true • problems with thinking about the biology of behaviour in terms of traditional dichotomies ◦ physiological-psychological debate ▪ damages or stimulation to the brain can product complex emotions • self-awareness ---> asomatognosia ---> result of brain damage ▪ animals are known to present some “human” behaviours • Chimpanzees ---> mirror to groom themselves + mark test response ▪ self-awareness! ◦ Difficulties with nature-nurture ▪ other factors than genetics began to show influence on behaviour • behaviour ---> combined control of both genetics and environment ◦ combine in an additive fashion ◦ how much does one factor contribute? ---> when both contribute • nature of interaction on development ◦ neurons are active long before they are fully developed ◦ the subsequent course of development depends on activity/experience ◦ experience continuously modifies genetic expression ▪ model of the biology of behaviour • behaviour is the product of interactions between: ◦ genetic endowment ---> product of evolution ◦ experience ◦ perception of current situation • human evolution ◦ Darwin ---> first to amass evidence but not first to bring about theory evolution ▪ fossil records ▪ structural similarities ▪ major changes due to selective breeding ◦ occurred through natural selection ---> heritable traits associated with high or low rates of survival/reproduction ---> repeated through generations ---> evolution of a species ▪ Fitness ---> ability for organism to survive ◦ just a theory? ---> scientific theory ---> best theory fitted for current evidence ◦ evolution and behaviour ▪ social dominance ---> usually established through combative encounters with men • dominant males copulate more than nondominant males • dominant females produce more and more healthy offspring ▪ courtship display • signal leading to copulation ---> copulation not likely to occur if pair fails ◦ species ---> isolated from others ---> break off when some barrier discourages breeding ---> evolution independently when cross-fertilization becomes impossible ▪ only suitible exchange is no longer possible ◦ course of human evolution ▪ evolution of vertebrates • water-dwelling organism ---> Chordates ---> dorsal nerve cords ---> bones to protect ---> vertebrates ▪ evolution of amphibians • transforming fins and gills into legs and lungs ---> amphibians ▪ evolution of reptiles • first to lay shell covered eggs and developed dry scales • spends first stage of its life in the watery environment of the egg than in the water ▪ evolution of mammals • fed young from mammary glands ---> mammals ---> stopped laying eggs and nurtured them in their own internal environments ◦ security to develop ▪ emergence of humankind • hominins ---> homo ---> erectus (extinct) and sapiens (human) ◦ hard to reconstruct ◦ lived inAfrica until about 50000yrs ago ◦ thinking about human evolution ▪ evolution does not happen in a straight line ▪ we are not up for evolutionary supremacy ▪ rapid evolutionary changes have been triggered by sudden environmental changes and adaptive genetic mutations ▪ only 1% of known species are in existence ▪ evolution does not progress to some perfunctory state ▪ not all behaviours and structures are adaptive ---> spandrels ▪ not all adaptive characteristics evolved into its current function ---> exaptations ▪ similarities among species do not mean common origins • homologous ---> similar but have common origins • analogous ---> similar but not common origins ◦ convergent evolution ---> unrelated species meeting the same environmental demands ◦ evolution of the human brain ▪ size and intellectual capacity was once stipulated to be related • larger animals have larger brains ---> more brain tissue to regulate them ▪ study evolution of different brain regions • increased in size • increased in size has occurred in cerebrum • convolutions have increased ◦ major structures connected in the same way may produce the same function in different species ◦ evolutionary psychology ▪ human behaviours through the consideration of the pressures that led to its evolution ▪ ex: promiscuity ---> indiscriminately copulating to forming mating onds • female mammals give birth to a few helpless young ---> adaptive that males stay with their young • polygyny---> males mating with more than one female ◦ low contribution from males ---> can produce lar
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