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WEEK TWO Evolution I and II (module, live lecture)

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Joe Kim

WEEK TWO (JAN. 20) Read Ch. 2 of the textbook. IN CLASS LECTURE EVOLUTION AND HUMAN BEHAVIOUR: SEX DIFFERENCES IN ROMANCE AND RISK-TAKING  Reproductive Fitness o A simple currency to evaluate reproductive success o Simple goal: get as much of our genetic material out there as possible… how do you go about doing that? This may drive some of the traits we have.  Outcome variance can drive different solutions to the same problems o High variance & low variance KEY ASSUMPTIONS  Simplifying human behaviour o Inputs  Decision Rules  Output  Stimuli from the environment  Decision Rules  Behaviour  1. Behaviour = psychological mechanisms + input  2. Evolved psychological mechanisms are coded in the brain  3. Evolved psychological mechanisms can be described as information processing devices SEX DIFFERENCES IN ROMANCE  Genes and Family Resemblances o Newborns look more like the male according to the mom’s family  If you are a woman and you have a baby, there is almost no uncertainty that it is your child… not the same case for the man unless you go through genetic testing.  We do not want to invest resources into children (genetic material) that is not ours  THE MAIN IDEA: Mothers and their families trying to convince the father to stick around  Thought Experiment: Looking for Love o Women typically list traits related to resource potential (i.e. car, money) o Men typically list traits related to fertility (i.e. nurturing, voluptuous….?) ROMANCE IN THE FRIEND ZONE Men Women 1. Are you attracted to yourYES NO friend? 2. Is your friend attracted to YES NO you? *: ・゚✧ 1 ✧゚・ :* 3. Would you date your YES NO friend?  In this example, we are looking at sexual attraction  People are misattributing their own opinion as the other’s DIFFERENT ADAPTIVE PROBLEMS  Metabolic demands of reproduction o Very costly for women  Parental investment  Genetic cuckoldry o Resources  offspring o Cuckoo birds leave their eggs in other bird’s nest o You don’t want to be cuckolded but you may want to cuckold others REPRODUCTION IN A NATURAL FERTILITY POPULATION  On average, men and women are having the same amount of children (2.04 vs. 2.14) o The centering around the mean for woman are much tighter o Some expected outcome but differences in variance (9.27 vs. 6.52)… can be attributed to differences in approach to the problem  Likelihood of agreeing to have sex with someone you find attractive as a function of time known o Increasing time = higher likelihood, less time = lower likelihood  Men are more likely to on any other time point other than 5 years  It takes much longer for a woman to say yes (6 months vs. 1 day) o For men, you can figure out physical beauty quickly o For women, it takes a longer time to figure out trustworthiness, resource potential, etc. MALE VOICE PITCH: HUMAN PEACOCK TALE  DEEP VOICE PITCH IS HERITABLE o YES – Testosterone almost exclusively determines voice pitch  DEEP VOICE PITCH HAS A COST o YES – Testosterone actually weakens the immune system  A lower voice pitch is generally rated more attractive than higher ones by women DIFFERENT PREFERENCES AT DIFFERENT TIMES  For women in their fertile point of menstrual cycle, they show preference for deeper voice pitch even more so MEDIA AND SOCIALIZATION VS. INNATE PREFERENCES  Most humans have been influenced/exposed to the media by some way… how do we know this isn’t a product of that?  The Hadza o Find hunter gatherer populations on the Earth (not influenced at all by media and human civilization) and ask about voice pitch o RESULTS: Direct Correlations! *: ・゚✧ 2 ✧゚・ :*  A lower voice pitch generally = higher reproductive success  Deep voice: ONE trait amongst MANY that women may be picking up on for mate selection NATURAL SELECTION, RISK TAKING, AND HOMICIDE  Poker chip example o Higher chance of winning less money o Lower chance of winning more money  Women more likely to choose lower risk situations COMPETITIVE RISK TAKING AS RESOURCE DISPLAY  One way of looking at it: I have so much and it doesn’t matter if I lose anyways  Another way: I NEED the resource, have to take the risk HOMICIDE RATES  CHICAGO 1965 – 1190, CANADA 1974 – 1990, ENGLAND AND WALES 1977-1990 o Women barely commit homicide and men do a lot o Maybe men engage in risky behaviours for resource display  Unemployed people commiting the most homicides at age 20-24 and throughout  Income inequality o Increase in income inequality = increase of homicide rate  Life expectancy o If life expectancy is lower, you are more like to commit homicide EVOLUTION I MODULE 1: INTRODUCTION TO EVOLUTION & PSYCHOLOGY  Biological sciences (including psychology), have shared agenda: to elucidate the adaptive designs of living beings  Interested in adaptations: the working parts (the functional systems and subsystems) that animals, including human beings, are made of MODULE 2: ADAPTATIONS  ADAPTATIONS: adaptations are biological traits that help an individual survive and reproduce in its habitat o Adaptations perform specific functions to make an organism better suited to its environment  ADAPTATION EXAMPLES o examples: eyes detect and analyze reflected light  Raccoons have extraordinarily sensitive front paws for sight at night  Some bat species can navigate at night through echolocation o AGAIN, adaptations are always FOR something, they serve identifiable functions! ADAPTATIONISTS  Biological traits aren't just morphological, perceptual processes and behaviors are also adaptations (i.e. how we manage to see, hear, or respond to stimuli) *: ・゚✧ 3 ✧゚・ :* o We look for processes (relevant adaptations) capable of accomplishing certain tasks  ADAPTATIONISTS use this label to describe hypotheses about adaptive function o Also psychologists who study development, behaviours, or perceptual systems PSYCHOLOGICAL ADAPTATIONS  "Higher" mental processes  Cognitive psychologists study things like: o Selective attention o Memory encoding o Memory retrieval o Word recognition  All tasks the mind needs to do its job = adaptive functions of mental activity  Cognitive psychologists = adaptationists --> analyze adaptive problems & tasks and look for adapatations that solve those problems ADAPTATIONS CONCLUSIONS Adaptive functions served by minds (i.e. control of movements, attraction to stimuli, aversion, etc.) evolved through natural selection MODULE 3: EVOLUTION BY NATURAL SELECTION INTRODUCTION TO NATURAL SELECTION  Adaptations emerge through activation of relevant genes in interaction with relevant aspects of the environment o How do they arise? o How do they become differentiated in related species? o How do they maintain their complex functionality despite random genetic mutations?  NATURAL SELECTION DARWIN & WALLACE  NATURAL SELECTION: differential survival and reproduction of organisms as a result of the heritable differences between them o 4 basic mechanisms of evolution: natural selection, mutation, genetic drift, mutation  Three essential components: o Individual Differences  Within any population, there is variation among individuals for any given characteristic o Differential Reproduction  Differences affect individuals' chances of surviving and reproducing (some individuals have more offspring) o Heritability  Traits that give rise to differential reproduction have genetic basis --> offspring of successful reproducers will have characteristics of parents  Example of Selective Transmission *: ・゚✧ 4 ✧゚・ :* Imagine population of blue and red fish Blue fish camouflaged in ocean and red fish get eaten more often Blue fish survive and reproduce better (differential reproduction) Blue fish have blue coloured babies because body colour is a heritable trait (heredity) Over successive generations, there will be selective transmission of heritable parental traits ... more blue fish!! Characteristics best adapted for survival and reproduction are reproduced at higher rates MODULE 4: NATURAL SELECTION IN THE WILD  STABILIZING SELECTION: selection against any sort of departure from the species-typical adaptive design (i.e. blue is common colour in fish population because it is adaptive and minimizes risk of predation)  Significant change in environment --> selection favours non typical traits --> evolutionary change( sometimes rapid)  Darwin's Finches  Beak shape and size of Medium Ground-Finch which lives on Daphne Island in the Galapagos Archipelago  Natural selection within a generation  1977: severe drought hit island and decimated vegetation (only large, tough seeds left)  Birds with big, heavy beaks able to eat and survived, birds with small beaks died  Large beaked survivors reproduced, beak size is heritable --> big beak babies  Conclusions  Most examples of natural selection observable in lifetime are small, subtle and can be reversed over time (i.e. when drought ended, average beak size returned to original)  Other changes that arise through natural selection are more permanent and form potential foundation for diversification of related species MODULE 5: REPRODUCTIVE SUCCESS = FITNESS *: ・゚✧ 5 ✧゚・ :* ADAPTATIONS PROMOTE REPRODUCTIVE SUCCESS  Natural selection does not simply favour those best at surviving (i.e. "survival of the fittest"), but those best at reproducing DARWINIAN FITNESS: average reproductive success of a genotype relative to alternative genotypes  Natural selection is really about differences in reproductive success, not just survival  "Survival of the fittest" is not so good a term as "fitness" (abstract property that natural selection tends to maximize) o Term describes how good particular genotype is at leaving copies of its genes in next generation relative to other genotypes (not always smartest, biggest or fastest) GENE FREQUENCIES  Fitness is competition between genotypes to leave copies of themselves  EVOLUTION: change in gene frequencies over generations MODULE 6: SEXUAL SELECTION  Sexually reproducing organisms: o Fusion of male and female gametes o Competition for mates  Natural selection acts on mate-finding and reproductive behaviours = SEXUAL SELECTION COURTSHIP DISPLAYS  Peacock & pea
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