Psychology 403 Topics in Evolutionary Psychology Dr M

Psychology 403: Topics in Evolutionary Psychology Dr. M. R. Snyder

Evolutionary Psychology • The approach • Old application, new formalization

Evolutionary Theories • Why/how do new organisms develop? • What drives change?

Evolutionary Psychology • • Multidisciplinary approach About 20 years old as a formalized field Theoretical approach Cosimides & Toobey (1992) – “Evolutionary Psychology Manifesto”

Evolutionary Theories Not New • Greeks – Heraclitus (6 th C. BC) • State of flux – Aristotle (4 th C. BC) • Development in prescribed direction • Medieval Europe – St. Thomas Aquinas (13 th C) • Human/lower animal differences

Eighteenth Century • George Leclerc, Comte de Buffon – Adaptations to fit environment pressures • Erasmus Darwin – Role of sexual reproduction • Jean de Lamarck – Inheritance of acquired characteristics • Georges Cuvier – Catastrophism

Charles Darwin • • • Provided causal mechanism Voyage of the Beagle (1831 -1836) On the Origin of Species (1859) Variation, inheritance, selection Artificial, natural, sexual Differential reproductive success

Social Darwinism • • Late 19 th century to present Directed, purposeful Teleological Political, social agenda

Sociobiology • E. O. Wilson • Systematic study of the biological basis of social behaviour

Evolutionary Psychology Issues • Are humans unique animals? • Gradual or sudden development? • Modularity of mind, or general information processor? • Environment of Evolutionary Adaptiveness (EEA)

Approaches • Evolutionary Psychology – Will the real EP please step forward? • Dual Inheritance Theory (DIT) • Human Behavioural Ecology (HBE)

Terms and Concepts

Genetics • Mendellian genetics – Gene, alleles – Particulate inheritance – Dominant or recessive – Homozygous or heterozygous – Genotype and phenotype • Polygenetic effects • Interaction between genes and environment

Darwinian Selection • Adaptive, maladaptive, neutral • Success – Not number of offspring, but number of reproducing offspring • Gene, individual, or group as level of selection?

Natural Selection • Survival value • Predator/prey, environment, parasitism, etc. • “Survival of the fittest”

Sexual Selection • Intrasexual selection – Within a sex • Intersexual selection – Between sexes

Genetic Diversity • • Heterozygosity Variability of offspring in the population Disease vector Sexual vs. asexual reproduction

r Values • Genetic relatedness • Probability of having the same gene due to common ancestor • r = 1. 0 – Self, identical twins • r = 0. 5 – Parent and child, siblings • r =0. 25 – Grandparent and grandchild

Inclusive Fitness • William Hamilton • Classical (direct) and “indirect” fitness • Role of r values – r. B>C – Phenotype and genotype

How to be Successful • Increase classical fitness • Increase inclusive fitness • Quantity vs. quality tradeoff

Male vs. Female Reproduction • Energy investment • Commonalities • Differences

Adaptationist Approach

Traits • An aspect of an organism’s phenotype • Physiological, behavioural

Adaptations • Process by which evolution modifies and generates traits that effect the spread of some genes over others • The end product of the process; i. e. , the traits selected by the evolutionary process

Spandrels • Byproducts • Not all traits are directly selected for • These traits are linked to other traits that were adaptations

Energy • • Finite Cost/benefit Energy budgets require trade-offs Expectation is that evolution selected for adaptations to energy budget that allows for maximization of fitness

Identifying Adaptations • Traits show “special design” if they perform a specific function well, and • It is difficult to postulate an alternative evolutionary process that led to the trait except for selection for this function • Inferential

Attractiveness as an Adaptation • Particular traits perceived as attractive by opposite sex • Benefits individuals’ reproductive fitness • Symons (1995): “Beauty is in the adaptations of the beholder. ”

Selection Benefits for Attractiveness • Genetic and resource benefits • Selection favoured those who possessed traits that predisposed them to mate with others who possessed traits that provided the benefits • Sexually selected traits

Cross Cultural Value • Buss (1989) surveyed from 37 cultures world wide • Value of physical attractiveness rated highly • Industrial, first world • Traditional (e. g. , Ache of Paraguay, Shiwiar of Equador, etc. ) • Also, cross-cultural agreement on who is attractive

Sexual Selection • A feedback system • One sex develops preference for trait • If it increases differential reproductive success, preference for trait spreads to offspring • Members of opposite sex that have the desired trait will also, therefore, spread the trait to their offspring

Intrasexual Selection • Competition between members of the same sex • Usually, perceived as male-male – Polygynous mating systems • However, in humans both male and female intrasexual selection

Intersexual Selection • Choice between the sexes • Sometimes called, “female choice” • Reproductive costs generally more expensive for females (limiting reproductive resource)

Mutual Mate Choice • Seen in species where both sexes invest heavily in offspring • Both sexes are selected to display desired traits • Seen in humans across time and cultures

Signaling Quality Traits • Traits that indicate something about an individual’s fitness • Honest signals are costly (Zahavi 1975) • “Handicap principle” • If you can afford the handicap, you must be of superior quality

Sensory Bias • May be a bias towards some trait in sensory system • May have nothing to do with mate choice • However, may inadvertently influence mate selection • Genes for some trait may be “piggybacked” into gene pool due to genes for sensory bias