Evolutionary Explanations of Contemporary Human Behavior Controversy Caused by Nature Nurture Debate 3 Evolutionary Approaches to Human Behavior Case Study Inbreeding Avoidance Evolutionary explanations of contemporary human behavior have been controversial o 2 misperceptions Behavior is entirely genetically determined Natural selection cannot lead to adaptations unless behavioral differences are caused by generic differences o Misunderstanding comes out of nature nurture debate nature phenotypic traits that are genetically determined and unchangeable genotype phenotype nurture phenotypic traits are shaped by environment experience and learning environment phenotype this debate reflects a general misunderstanding of phenotype Genotype environment phenotype o The nature nurture debate is misguided because the vast majority of traits reflect interaction between genes AND environment Example 1 stature Example 2 language Heritability of adult stature is 50 Genes affect development of mechanical and cognitive machinery to process sounds and symbols Environment affects what language will be acquired what information will be exchanged etc immutable or that humans are slaves to their genes o Evolutionary basis for behavior does not imply that behavior is Behavior is more plastic than morphology or physiology Natural selection often favors behavioral flexibility Hamilton s rule rb c requires animals to adjust Sexually selected infanticide predicts males will behavior in different contexts protect infants in some circumstances but kill them in others what others do Ones behavioral strategy is sometimes based on 3 evolutionary approaches to human behavior o Evolutionary psychology How has selection shaped human psychological mechanisms what we use to take decisions Assumes that modern conditions are different than those in which the human mind evolved The human mind was shaped by challenges faced by our hunter gatherer ancestors during the Pliocene and Pleistocene 2 crucial assumptions Complex behavioral adaptions evolve slowly The details of past conditions are known as Environment of Evolutionary Adaptedness EEA strategies different conditions gatherers How has natural selection shaped human behavioral Focus fitness outcomes of behavioral strategies in HBE research focuses on strategies of recent hunter Behaving optimally how long to hunt What to Simple mathematical models provide precise hunt Where to hunt predictions that can be tested against empirical date o Human behavioral ecology Common critiques of HBE It is implausible that people make optimal decisions o Calculations are complex and require perfect knowledge on the part of foragers HBE ignores mechanisms for decision making o Knowledge of psychological mechanisms ignored by HBE is needed to explain departures from optimal predictions o Cultural evolution How does cultural transmission affect frequencies of Does not assume that observed behaviors are behavioral strategies in a population mistakes held over from the EEA Evolutionary psych or that all behaviors are adaptive HBE Evolution human behavior case study inbreeding avoidance o In general primates avoid mating with close kin o But how can we explain this behavior Is it learned or o Many deadly diseases are caused by being homozygous o Inbreeding increases chance of offspring with 2 copies of o EX In human societies matings among close kin are strongly instinctive recessive sickle cell anemia deleterious recessive allele avoided even outlawed There are no known human societies with regular matings between siblings or between parents and offspring avoidance in humans o Several different mechanisms may explain inbreeding Phenotypic cues about genetic similarity kinship Age class people your age are not your parents Sexual aversion to people one grows up with Westermarck effect childhood association stifles sexual attraction Cultural rules about sex and marriage Disgust o Taiwanese minor marriages provide evidence for Westermarck effect What is a minor marriage How have they been problematic Lack of sexual interest Lower female fertility Higher infidelity rates Higher divorce rates Culture social learning and human evolution Cultural Evolution approach to human behavior What is culture How do we study it from an evolutionary perspective Individual learning vs social learning Different forms of social learning The dark side of observational learning What is culture o Culture is Learned Shared From other people Cultural evolution requires population thinking Population thinking about culture change How does the ability to acquire ideas beliefs and values from others via social learning affect the frequencies of behaviors at the level of a population through time Ex tattoos on basketball players What is social learning How does it occur Symbolic Dynamic and error Individual vs social learning o Individual learning a behavior is acquired after period of trial Can be expensive time and energy and dangerous o Social learning a behavior is acquired by observing or Social learners do not ay a cost for acquiring the interacting with another individual Different forms of social learning behavior o Social facilitation the activity of one individual indirectly increases the probability that other individuals will learn the behavior on their own local stimulus enhancement o Observational learning a na ve individual learns by observing and imitating an experienced individual a teacher Innovations can be passed on and people have a cumulative nature Cumulative culture provides humans the behavioral flexibility to live almost anywhere and organize our societies almost any way In short the phenotypic flexibility provided by cumulative culture may help explain the relatively recent success of hominins Unbiased cultural transmission a na ve individual chooses to copy a behavior or a teacher at random from within the population Biased cultural transmission an individual copies a particular behavior or a particular teacher for a reason showing some bias Note that this reason may not even be conscious nor does it necessarily lead to the adoption of an adaptive behavior Direct bias Content bias do what appeals to your personality or preconceived notions may be the easiest for you to learn or understand result for you Results bias do what provides the best Prestige bias do what prestigious person Indirect bias does Frequency dependent bias Conformist bias do what the majority of Anti conformist bias