Genetic and Evolutionary Foundations of Behavior Chapter 3 Darwin s Theory 150 years ago Charles Darwin proposed a theory of evolution that explains both the differences and the similarities between species Today evolutionary scientists discuss the application of evolutionary theory to explain behavior How Genes Affect Behavior Gene for Genes provide the codes for protein Structural proteins forms the structure of cells Enzymes controls rate of chemical process in cells DNA Composed of a series of amino acids Templates for RNA serves as templates for proteins Genes are segments of DNA Non coding DNA Junk DNA passed on but no apparent effect on development may regulate coding DNA Coding genes codes for proteins vs Regulatory genes moderates by activating or suppressing coding genes Genes Work Only through Interaction with the Environment Environment is every aspect of an individual and his her surroundings except the genes themselves There is continuous complex interplay between genes and the environment Genotype vs Phenotype Genotype Phenotype The set of genes that an individual inherits Observable properties of the body and behavioral traits How Genes Are Passed Along through Reproduction DNA exists in chromosomes The normal human cell has 23 chromosome pairs All humans have 22 of these pairs the last pair is sex chromosomes XX for females One member of each of these pairs comes from one parent the other member of the XY for males pair comes from the other parent Mitosis and Meiosis Mitosis Meiosis cells When cells other than reproductive cells divide to create identical cells Reproductive cells replicate and divide many times to create non identical Genetic Diversity of Offspring Genes have a better chance of survival if they are rearranged at each generation Twins are the only offspring that are not diverse Identical twins Fraternal twins Homozygous and Heterozygous When two genes at the same locus on a pair of chromosomes are the same the individual is homozygous at that locus 1 3 and 5 When the two genes are not the same the individual is heterozygous at that locus 2 4 Alleles different genes that can occupy the same locus and thus can potentially pair with each other Dominant and Recessive Genes A dominant gene is one that will produce its observable effects in either the homozygous or heterozygous condition A recessive gene is one that will only produce its observable effects in the homozygous condition Mendelian Pattern of Heredity Mendel came up with the idea that genes come in pairs and that one can be dominant over the other He discovered that some behaviors are affected by a single gene Fearfulness in dogs KE family language disorder Selective Breeding Modifying a specific behavior or characteristic by mating individuals with or without the specific characteristics Example Tryon s classic maze rats Polygenic Behavioral Characteristics Many human behaviors are complex and are affected by multiple genes and interactions with the environment Evolution by Natural Selection Origin of Species Artificial selection Human controlled selective breeding Natural selection Selective breeding in nature Darwin s essential point Individuals of a species vary in the number of offspring they produce Traits that increase of offspring will be selected for Traits that decrease of offspring will be selected against Genetic Diversity Provides the Fodder for Natural Selection There are two sources of the genetic variability on which natural selection acts Reshuffling of genes during reproduction Mutations Errors that occasionally and unpredictably occur during DNA replication Environmental Change Provides the Force for Natural Selection Evolution is spurred by environmental changes Environment can cause appropriate mutations that change and promote natural selection Grant and Grant s work on finches Peppered Moth Evolution Has No Foresight Evolutionary paths are not working toward some predetermined end Humans are not the most evolved species Natural selection is not a moral force Natural Selection as a Foundation for Functionalism Functionalism The attempt to explain behavior in terms of what it accomplishes for Tries to answer how a trait helped ancestral members of the species survive and the behaving individual reproduce Ultimate and Proximate Explanations Ultimate explanations Functional explanations at the evolutionary level Proximate explanations Explanations that deal with the mechanism in the immediate conditions Example Songbirds Limitations on Functionalist Thinking Some traits are vestigial Some traits are side effects of natural selection for other traits Some traits result from chance were are inconsequential and not selected for Evolved mechanisms cannot deal effectively with every situation Natural selection develops mechanisms triggered by general not specific conditions Natural selection doesn t create mechanisms capable of distinguishing among specific conditionings and triggering them only when it is useful and not harmful e g guilt Species Typical Behaviors in Humans Human emotional expression Darwin Ekman and Friesen Eibl Eibesfeldt Role of learning in developing species typical behavior E g language walking Biological preparedness and species typical behavior E g eyebrow flash and moderation by culture Natural selection prepares organisms to learn and develop specific traits or characteristics in specific ways at specific times E g language walking taste aversion learning imprinting etc Cross Species Comparisons Homologies Physical mechanisms of behavior Evolutionary pathways of species typical traits Analogies Convergent evolution Fallacies to Avoid Naturalistic fallacy Natural moral right Social Darwinists Deterministic fallacy Genes determine behavior No species is more evolved than another Genes do not influence behavior and mental processes directly The internal environment may mediate the influence of genes e g sex linked effects Genes may moderate or interact with the direct environmental influence on behavior e g Biological prepared learning language imprinting perhaps even intelligence