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Psychology 4000 Evolutionary Psychology Dr Darren Hannesson Lecture 2 What is evolutionary psychology? The theory of evolution by natural selection natural selection variation inheritance selection objections to evolution The modern synthesis: Evolution and genetics mendelian genetics genes and DNA Updates to evolutionary theory Misunderstandings about evolution 1 What is evolutionary psychology? a sub-field of biopsychology the study of behaviour and mind in terms of their underlying biological mechanisms genes, development, anatomy & physiology, evolution What is evolutionary psychology? Field of study = Subject matter (question) + explanation (answer) “the study of behavior and mind in terms of their function as solutions to adaptive problems faced during human evolutionary history” history” “the study of human evolutionary history and how it may have generated behavior and mind as solutions to adaptive problems” problems” 2 What is evolutionary psychology? Examples Why do women show a preference for mating with older men? Explanation should be in terms of selective pressures that could have made such a mating preference adaptive during our species evolutionary history What impact might hunting have had on human psychology? Explanation should be in terms of adaptive problems that arose as a result of using hunting as an important means of food acquisition and how current psychological traits may have helped solve these problems The theory of evolution by natural selection evolution change in species over time emerged to explain to three fundamental observations there are a wide variety of species on earth the characteristics of each species are particularly suited to achieve achieve distinct functions species share a remarkable number of structural and functional characteristics Lamarckian evolution transmission of acquired characteristics 3 The theory of evolution by natural selection Charles Darwin The theory of evolution by natural selection Darwin’ Darwin’s finches 4 The theory of evolution by natural selection principles of population results in a struggle for existence “winners” winners” are those with favourable variations repeated over generations this results in new species The theory of evolution by natural selection 3 key elements of Darwin’s theory variation inheritance selection 5 The theory of evolution by natural selection currency of evolution is “differential reproductive success” do you produce more reproductive offspring than the “Joneses” Joneses” what about survival? The theory of evolution by natural selection objections to evolution emotional religious rational 6 The modern synthesis of evolutionary theory and genetics genetics helps account for two aspects of evolution: heritability variability The modern synthesis of evolutionary theory and genetics Mendelian Genetics Mendel’s pea experiments (http://www2.edc.org/weblabs/Mendel/MendelMenu.html) bred peas with seeds that were green or yellow 7 The modern synthesis of evolutionary theory and genetics Mendelian Genetics Proposed particulate inheritance genes the unit of heredity each person is made from a complete set human genes each person has two copies of this set The modern synthesis of evolutionary theory and genetics Mendelian Genetics Dominant vs recessive Genotype vs phenotype 8 The modern synthesis of evolutionary theory and genetics Biochemistry of Genetics genes are written in the language of a molecule: DNA (deoxyribonucleic acid) DNA is constructed from Sugar backbone Paired nucleotides two strings of sugar backbones interlinked by cross matched base pairs twisting in the form of a double helix each molecule of DNA forms a complex with some proteins and forms a chromosome each species has a characteristic # of chromosomes The modern synthesis of evolutionary theory and genetics The genetic code genes do one of two things: code for long strings of amino acids (structural genes) or they regulate the function of other genes the “code” code” consists of a sequence of 3 base pairs (a codon) sequence of codons serves as template for stringing amino acids together to form proteins Enzymes Structural proteins 9 The modern synthesis of evolutionary theory and genetics Inheritence Meiosis generates gametes that contain one copy of each chromosome Contains 1 full set of genes Offspring are created when one gamete is “fertilized” fertilized” by the opposite sex gamete creating a zygote with two sets of chromosomes Zygote has two copies of each gene May be homozygous (same - yy) yy) or heterozygous (different Yy) Yy) The modern synthesis of evolutionary theory and genetics Sources of variation Sexual reproduction Recombination crossing over meiotic errors Mutation mitotic errors Environmental effects Penetrance PKU 10 The modern synthesis of evolutionary theory and genetics Genes and gender gender is determined by one pair of chromosomes called sex chromosomes XX Æ female; XY Æ male all others are called autosomal chromosomes sexsex-linked genes genes on X chormosome will be apparent in different frequencies in males and females sexsex-limited genes genes that have an effect on oneone-sex but not the other Updates to evolutionary theory sexual selection natural selection emphasized adaptations that promoted survival some traits seem to decrease survival traits that directly promoted reproductive success could be highly adaptive 11 Updates to evolutionary theory sexual selection Intrasexual selection traits that facilitate competition between members of the same sex for access to mates Updates to evolutionary theory sexual selection Intersexual selection traits that promote being selected as a mate by the opposite sex 12 Updates to evolutionary theory Inclusive fitness classical fitness = an individual’s reproductive success BUT selection operates at the level of the gene not the individual genes that promote their own survival/reproduction will be selected for regardless of “who carries them” them” therefore … inclusive fitness = classical fitness + effects on survival/reproduction of kin (since they also carry many of your genes) Updates to evolutionary theory Adaptations solutions to specific problems that impacted reproductive success Must be … Reliably expressed Efficient Economical 13 Misunderstandings about evolution Adaptations are strictly genetically determined Instead: adaptations prepare response forms responses are both elicited and shaped by the environment Misunderstandings about evolution Adaptations produce inflexible, unmodifiable traits or behavior Instead: organisms alter their environment organisms have a repertoire of adaptations 14 Misunderstandings about evolution Adaptations should produce optimal designs “why aren’t we perfect?” Instead several factors limit the likelihood of optimal designs evolutionary lag time and environmental variation costs biological system constraints Misunderstandings about evolution Adaptations should produce optimal designs “why aren’t we perfect?” evolutionary lag time and environmental variation 15 Misunderstandings about evolution Adaptations should produce optimal designs “why aren’t we perfect?” costs Misunderstandings about evolution Adaptations should produce optimal designs “why aren’t we perfect?” biological system constraints 16