relationships- evolutionary explanations Flashcards
what is a relationship?
a continuing and often committed association between two or more people
what is natural selection?
genes which are advantageous for survival are naturally selected. genetic mutations give the individuals an advantage that helps to survive and reproduce
what is sexual selection?
form of natural selection, characteristics that increase reproductive success are passed on and may become exaggerated through generations
define anisogamy
sex differences between male and female sex cells (gametes)
consequence of anisogamy
no shortage of fertile males but there are of fertile females (‘rarer’ resource)
what is intersexual selection?
female ‘choosiness’
-develop and display traits or behavior patterns to attract the opposite sex
-females produce few eggs, only fertile for 25yrs ovulate one egg per month- large reproductive investment
-can be sure of maternity
-makes sense to engage in monogamy
-quality over quantity
-look for useful qualities such as resources that will help once offspring born
Trivers on intersexual selection
Trivers (1972)
-argues females make greater commitment before, during and after the birth of her offspring so more selective
-female preference determines what features are passed onto offspring, this gradually becomes more exaggerated through generations (a runaway process).
Fisher on intersexual selection
Fisher (1930)
-sexy sons hypothesis
-genes we see today are those with enhanced reproductive success
-female who mates with a male who has this certain ‘sexy’ trait will have sons with this trait
-sons will be selected by other females and trait will be passed on and sexy trait perpetuated
what is intrasexual selection?
-members of the same sex compete with one other for members of the opposite sex
male competitiveness
-can fertilise many females w/ very little cost to reproductive potential
-quantity over quality
-for ancestors couldn’t be sure of paternity
-makes evolutionary sense for males to maximise no. of potential pregnancies
-males look for females who display signs of fertility- good health, youth, childbearing hips
-these females will enhance their chance of reproductive success
what are the behavioural consequences of intrasexual selection?
competitive behaviours are more likely to be passed on e.g. deceitfulness, intelligence and aggression. these can be argued to be adaptive strategies.
ao3: limitation of evolutionary explanation (mate choice) from Penton-Voak et al.
-mate choice may be more complicated than suggested
-penton-voak et al. (1999) females preferences change across the menstrual cycle. prefer a partner w/ strong masculine features when ovulating but one w/ feminine features as a long term partner
-masculine appearance may suggest healthier immune system- better to pass to offspring. while feminine appearance suggests kindness and parental co-operation, desirable in a long term partner
-not a full and comprehensive explanation of mate selection
ao3: strength of partner preference from Buss
-supportive empirical evidence for partner preference
-Buss (1989) survey of over 10,000 adults in 33 countries. found females reported valuing resource-based characteristics when choosing a partner whilst men valued good looks and preferred younger partners
-evidences the theory that females choose based on the quality of resources, have to be more selective as limited supply of eggs
ao3: strength of partner preference from Singh
-studied preferred waist-to-hip ratio as sign of female fertility. waist to hip ratio of winners of miss America contest for a decade found men generally found any waist and hip sizes attractive as long as ratio 0.7
-female having larger hips and slim waist achieves this ratio- men unconsciously interpret as women is fertile but not currently pregnant.
ao3: strength of partner preference from Waynforth and Dunbar
Waynforth and Dunbar (1995) researched ‘lonely hearts’ columns in American newspapers
-found women tended to describe themselves as physical attractiveness and youth
-men advertised their intelligence more than women
ao3: strength of partner preference from Clarke and Hatfield
