Transcript Chapter 3
Chapter 3 Evolution and Genetics Where did we come from? Human history is relatively short Evolutionary history is extremely long Species A species is a reproductively isolated breeding population More than 95% of all species that have ever lived are now extinct Distal and Proximal Causes of Behavior Distal (ultimate) causes: causes of behavior rooted in evolutionary and genetic determinants Proximal (nearby) causes: Causes of behavior that focus on immediate, local, (psychological and sociological) determinants. Crying behavior shows both distal and proximal causes: Darwin’s Theory of Evolution On the Origin of Species by Means of Natural Selection (1859) Evolution: existing species of life on earth are the end result of a process of natural selection Adaptation Any characteristic that improves the "fit" of a plant or animal with its environment, thereby increasing its chances of transmitting genes to the next generation. Natural Selection The means by which organisms adapt to the environment and reproduce differentially. Selective Pressure Any feature of an environment that allows one organism to have reproductive advantage over another. Lamarckian Evolution The theory that genetic changes can occur in populations through the inheritance of characteristics acquired during a lifetime. Cataclysmic Disasters Mass extinction due to natural calamities E.g. asteroid impact resulted in sudden extinction of the dinosaurs Genetics and Heredity Genes The basic units of heredity Genotype The genetic constitution of an individual organism Phenotype The physical expression of features in an organism that results from the interaction of its genotype with the environment Mendel’s Experiments: Breeding peas with dominant and recessive traits results in predictable proportions of offspring Aa bred with Aa results in 75% dominant phenotype, 25% recessive phenotype Mendel’s Experiments AA Aa Aa Aa Aa Note: These three offspring appear identical. aa Deoxyribonucleic Acid (DNA) A double-strand, helixshaped structure containing genetic material. The basis of the chromosome: A structure in the nucleus of a cell that carries genetic information Genetic Relatedness Degree of Relatedness Individual Organism an identical twin Percentage of genes shared with you 100% first degree a sibling (brother or sister) a mother or father a child 50 50 50 second degree a grandparent a grandchild a half-brother or half-sister an aunt or uncle a niece or nephew 25 25 25 25 25 third degree a first cousin 12.5 a stepchild a spouse 0 or ? 0 or ? Genetic Relatedness Homo Sapiens has a shared genetic history with all its ancestors We also have a shared genetic relationship with other animals Up to 98.4% genetic similarity to some chimpanzee species Genetic Variability Meiosis The process of cell division that produces sex cells (sperm and egg) containing one of each pair of chromosomes “Crossing over” results in genetic variability How can genes influence behavior? Genes can only produce proteins Proteins create structures like the brain Genes and Environment Phylogenetic History The evolutionary history of a specific group of organisms Ontogenetic History The history of an animal’s entire development, from fertilization through death Extragenetic History Information in the form of cultural wisdom, including oral and written history, that is passed across generations Nature vs. Nurture Species-specific behaviors adaptive, innate response patterns typical of a species Learning Changes in behavior resulting from experience Behavioral Genetics The study of how genes, interacting with environments, affect behavior E.g. Emotionality in dogs Breeding fearful basenji dogs with sociable cocker spaniels results in an F2 pattern of offspring similar to that seen in Mendel’s experiments 3/4 Fearful, 1/4 sociable Fearfulness is a dominant trait Behavioral Genetics Obesity in mice Behavioral Genetics Obesity in mice Inbreeding heavy mice results in heavier offspring An example of a polygenic character A character that varies in a continuous manner, presumably caused by the effects of many genes Ethology The study of species-specific behaviors Ethologists are interested in instinctive behaviors Patterns of behaviors that are common to a species Ethology Appetitive Behaviors Preliminary activities that precede and lead to consummatory behaviors Consummatory Behaviors Innate "survival" behaviors such as copulating and eating Imprinting A highly adaptive innate behavioral process that involves the rapid development of a response to a specific stimulus at a particular stage of development E.g. following behavior in goslings Fixed Action Patterns Programmed sequence of speciesspecific behaviors that are triggered by a particular stimuli E.g. egg-retrieval in geese Fixed Action Patterns Sign Stimulus A specific environmental stimulus that triggers innately organized behaviors E.g. sight of egg Innate Releasing Mechanism A neural mechanism that triggers an innately organized motor program Species-Specific Defense Reaction An innately organized hierarchy of defense behaviors elicited by signals indicating potential danger E.g. “freezing” and fleeing from danger in rats Comparative Psychology The study of the motivation and behavior of animals in order to identify similarities and differences among them Morgan’s Canon: One should not attribute complex psychological processes to non-human animals if a simpler explanation is available Anthropomorphism The attribution of human characteristics to animals Zoomorphism The attribution of animal qualities to humans Contact Comfort Harlows Baby monkeys prefer contact with soft “mother” over “mother” that merely gives food Harlow picture Pair Bonding A strong and enduring affection that unites an infant with a parent Social isolation disrupts pair bonding and later adult interactions (Harlows) Neuroethology The study of the relationship between the nervous system and consummatory behaviors E.g. brain areas controlling song in birds change in size as a function of hormone levels Sociobiology The study of the genetic determinants of social behavior Evolutionary Psychology The study of human and animal minds and behavior from the perspective of evolutionary theory. The “Selfish Gene” - Dawkins Human behavior can be viewed as an attempt by our genes to propagate themselves Kin Selection The theory that one promotes the well-being and inclusive fitness of a genetic relative because of shared genes Inclusive Fitness The fitness of an individual and related individuals (who carry many of the same genes) Altruism A behavior that helps another individual but may diminish one’s survival or reproductive potential The likelihood of altruism correlates with the one’s genetic relationship to the individual receiving help Mating Patterns Monogamy Polyandry Polygyny Polygandry Mating Patterns Parental Investment Mating patterns are influenced by how much an offspring’s survival costs one parent or another E.g. carrying a child through gestation vs. providing sperm E.g. time spent guarding mate or offspring Human Mating Systems