evolutionary explanations

• darwin suggested we have evolved in order to?

  1. survive - natural selection
  2. reproduce - sexual selection
• relationships & evolution?

  • we have evolved to form relationships & choose partners which either enhance our reproductive success so we can pass our genes or to increase our chances of survival
• define sexual selection?

  • process by which characteristics are selected in a species because they attract opposite sex & increase chances of reproduction
• 2 types of sexual selection?

  1. intersexual selection
  2. intrasexual seletion
• darwin & sexual selection?

  • he suggested that some bodily features & behaviours exist as theyre valued by opposite sex
  • they may not be advantageous to survival - increase likelihood of animal reproducing & passed onto offspring
• intersexual selection - choosing a mate?

  • refers to evolution of traits that influence mate choice
  • certain characteristics are preferred by opposite sex
  • those possessing these traits will attact more mates - sexually selected & passed on
• sexy sons hypothesis?

  • sexy traits will be passed onto offspring which in turn will make their children more attractive to opposite sex so will enhance their reproductive success - can pass on their genes
• intersexual selection & reproductive behaviour?

  • preferred reproductive behaviour of females
  • have limited number of eggs
  • trivers 1972 - female has to invest more into offspring in terms of time/commitment/other resources compared to males
  • women prefer long term mating - being with only 1 sexual partner & being with them for long time
  • quality over quantity!!
• females mate preference?

  • as she has to invest more she has more to lose if she chooses wrong partner
  • has to be pickier when comes to choosing mate
  • women have genetically evolved to select male who is genetically fit & healthy & has resources & willing to provide these resources for her potential offspring
• waynforth 2005?

  • found that women prefer men with square jaw, ridged eyebrows, small eyes & symmetrical face
• intrasexual selection - fighting for dominance

  • members of 1 sex compete with members of same sex for access to members of opposite sex
  • when successful reward is to mate with opposite sex & pass on their genes - next generation have desirable traits
  • enables offspring to inherit strength to further be able to compete with same sex - more likely to mate & pass on genes
• intrasexual selection & reproductive behaviour?

  • preferred reproductive behaviour of males
  • minimal effort is required to produce enough sperm to theoretically fertilise many women
  • male does not have to invest much into offspring after birth
  • males likely to take higher number of sexual partners - increases chances of passing on genes
  • prefer short term mating - engage in more casual sex
  • quantity over quality!!
• males mate preference?

  • likely to go for young & youthful looking women
  • theyre more likely to be fertile
• singh 1993?

  • found that across cultures theres preference for females waist-hip ratio of 0.7 - typical hour glass figure
  • signals to males that female is over age of puberty & not pregant & associated with better health & reproductive success
• 3 * of evolutionary explanations?

  1. evidence from dunbar 1999
  2. evidence from buss 1989
  3. evidence from clark & hatfield 1989
• 2 X of evolutionary explanations?

  1. oversimplified
  2. methodological problems
• * evidence from dunbar 1999 evolutionary?

  • conducted content analysis on lonely hearts advert in newspapers
  • found that most men wanted woman who was younger than themselves
  • women tended to seek older men - 1/4 women sought resources
  • supports idea that females prefer to choose mate who enhances reproductive success by providing for them & their offspring
  • men prefer more fertile looking women in order to pass on genes
• * evidence from dunbar 1999 sexual selection & reproduction?

  • conducted content analysis on lonely hearts advert in newspapers
  • found that most men wanted woman who was younger than themselves
  • women tended to seek older men - 1/4 women sought resources
  • supports idea that women will choose mate who will provide quality over quantity in terms of reproductive behaviours
  • men select mate who appears more fertile so they can engage in short term mating to pass on their genes to many offspring
• * evidence from buss 1989 evol?

  • asked males & females what they look for in marriage partner used over 10000 people from 33 countries
  • found females said were looking for males who could financially provide, tall, strong & healthy, older than them & who had symmetry of face & body
  • males said were looking for females who were younger,healthy,physically symmetrical with good WHR
  • supports idea males & females look for diff characteristics in opposite sex - increase chances of survival & reproductive success - said to have evolved to look for
  • men look for young women & women look for resources
• * evidence from buss 1989 sexual selection?

  • asked males & females what they look for in marriage partner used over 10000 people from 33 countries
  • found females said were looking for males who could financially provide, tall, strong & healthy, older than them & who had symmetry of face & body
  • males said were looking for females who were younger,healthy,physically symmetrical with good WHR
  • supports idea that females select mate who will protect & provide when they have child & be part of long term mating
  • men select mate who appears younger so more fertile
• * evidence from clark & hatfield 1989 evol?

  • conducted study - investigate diff in reprod behaviour between men & women
  • attractive male & female approached total strangers on uni campus said "hi ive been noticing u around campus & i find u very attractive" then asked series of q "would u have sex w me tnt?"
  • 75% men - yes & no women said yes
  • supports idea females evolved to choose mate takes part in lt mating to protect them & offspring - reject casual sex
  • men likely to take part in st mating w young attractive women - want to pass on genes to many offspring - likely to agree in casual sex
• * evidence from clark & hatfield 1989 sexual selection?

  • conducted study - investigate diff in reprod behaviour between men & women
  • attractive male & female approached total strangers on uni campus said "hi ive been noticing u around campus & i find u very attractive" then asked series of q "would u have sex w me tnt?"
  • 75% men - yes & no women said yes
  • idea that men choose to partake in st mating to pass on genes to lots of offspring is supported
  • supports ides that women less likely to partake in st mating as they have more to lose if choose wrong mate & have higher parental investment
• X oversimplified?

  • theory does not explain all couples
  • eg cannot explain homosexual relationships where its impossible for either of pair to find other attractive as a result of evolution where we look for traits that increase our reproductive succes & chances of survival
  • cannot account for lots of relationship types which exist in modern society
  • means it cannot be fully accurate as it doesnt provide valid explanation for these relationships so other factors must be involved
• X methodological problems?

  • due to fact that in order to study mate preferences & reproductive behaviours of males & females we need to use self report techniques - questionnaires
  • means that results may rely on honesty of p & accuracy of their answers
  • they are likely to lie about such sensitive topics - preferred mating preferences & casual sex to gain social desirability.
  • method of investigation used can easily lack accuracy & therefore explanations for partner preferences & relationship between sexual selection & human reproductive behaviour may not be accurate