evolutionary explanations

• what is the only part of us that survives for many generations?

  genes
• from a biological perspective, what is purpose of life?

  to ensure the survival of our genes
• how can we ensure the survival of genes?

  pass as many genes as possible into the next generation
• in the phrase 'survival of the fittest' from Darwin's theory of natural selection, what is meant by 'fittest'?

  best adapted - so if an individual is well adapted to survive in their environment, they'll be the healthiest, will reproduce most successfully (pass their genes down) and will live the longest
• genes that code for successful, adaptive characteristics are said to be ? by natural selection

  selected for
• genes that code for maladaptive characteristics that lead to the individual's death or failure to reproduce are ? by natural selection

  selected against
• what is human reproductive behaviour?

  any behaviour that relates to opportunities to reproduce + pass our genes on to the next generation e.g. mate choice and mate competition
• what is reproductive fitness?


  the extent to which an individual's body/behaviour increases the chances of them attracting a mate + successfully reproducing
• outline the basis for evolutionary explanations of reproductive behaviour


  genes that increase reproductive fitness will be selected for repeatedly so will be found in all members of a species
• what is sexual selection?

  a form of natural selection where genes increase successful reproduction but not through increasing survival - they're selected for by helping to attract a mate + helping defeat competitors for access to prospective mates
• what does sexual selection explain?

  why some features continue in a population even if they're a disadvantage to survival e.g. a peacock's tail
• explain how sexual selection works on males

  sperm is small and doesn't require much energy to produce and is biologically 'cheap'produced from puberty to old age continuouslyno shortage of fertile males SO males need to compete with each other for access to the female (fertility in females may be rare)
• explain how sexual selection works on females

  eggs are large12-13 produced a yearrequire lots of energy to produce and are biologically expensive produced for a limited time - puberty to menopausefertile females are rare biological 'resources'SO females have to be choosy about which male will father their offspring
• what is inter-sexual selection + what gender is it generally seen in?


  gene is selected for because of behaviour of other sex seen in femalesit's more important for females to choose the best quality mate as they need to invest in pregnancy, childbirth and raising the childinter = between
• what is intra-sexual selection + what gender is it generally seen in?


  gene is selected for because of behaviour of same sex intra = within seen in malesmakes you more able to compete with members of the same sex for access to a mate best strategy for getting many as many genes as possible into the next generation = fertilise as many females as possible
• any characteristic that helps a male overcome competition + gain access to a fertile female an protect her from competing males will be selected for - what has this led to?

  differences in body shape and size between the two genders (males may need to physically fight other males for access to a female - increased muscle mass)differences in aggression between the two genders (aggressive males would be more successful in competition with other males)preference for youth (males shouldn't waste resources competing for non-fertile females so they show a preference for younger females + signs of youth e.g. large eyes, rounded, smooth features
• give two strengths of evolutionary explanations of human reproductive behaviour

  :) predictions about female 'choosiness' supported by research evidence - Clark & Hatfield - when propositioned on a uni campus, 0 females agreed to sleep with another student, 75% of males agreed immediately - females more choosy, predictions are valid:) gender differences in reproductive strategy supported by research evidence - Buss surveyed over 10,000 adults in 33 countries - found females valued indications of good resources e.g. good financial prospects / males valued indications of good reproductive capacity e.g. youth - cross cultural study + large sample size, findings are due to genes - evolutionary theory is valid
• give two limitations of evolutionary explanations of human reproductive behaviour

  :( ignores effects of social/cultural influences - women's mate choices may no longer be resource based as they have larger role in the workforce + access to birth control - explanations are oversimplified :( can't explain homosexual relationships where one partners genetics won't be passed into the next generation - explanations are oversimplified