sexual selection and human reproductive behaviour Flashcards
define sexual selection.
an evolutionary explanation for partner preference.
explains why some characteristics that might appear disadvantageous actually have an advantage in human reproductive behaviour because they are attractive to potential mates, or provide an advantage over competitors for reproductive rights.
attributes or behaviours that increase reproductive success are passed on and may become exaggerated over succeeding generations of offspring.
define human reproductive behaviour.
any behaviours which relate to opportunities to reproduce and thereby increase the survival chances of our genes.
it includes the evolutionary mechanisms underlying our partner preferences such as mate choice and mate competition.
outline anisogamy.
differences between male and female sex cells (gametes).
male - small, mobile, created continuously in large numbers.
female - large, static, produced at intervals for a limited umber of years.
a consequence for mate selection is that there is no shortage of fertile males but a fertile female is a rare resource.
gives rise to two mating strategies, meaning there’s two types of sexual selection - inter sexual and intra sexual selection.
outline inter sexual selection.
between the sexes - males use to select females and vice versa.
preferred strategy of the female - quality over quantity.
ova are rarer than sperm and require greater energy to produce. females make a greater investment of time, commitment and other resources during and after birth of offspring.
consequences of choosing wrong partner more serious for female - pays to be more choosy. optimum strategy is to pick a genetically fit partner who is able to provide resources. leaves males competing for opportunity to mate with fertile females.
this choice determines features passed to offspring - e.g. if height is attractive, over generations of females, height would increase in the male population because females will mate with tall partners and, over time, produce sons who are taller with each generation and daughters who prefer tall partners - known as runway process (sexy sons hypothesis).
outline sexy sons hypothesis - Fisher (1930).
a female mates with a male who has desirable characteristics - ‘sexy trait’ is inherited by her son.
increases likelihood that successive generations of females will mate with her offspring.
outline intra sexual selection.
within each sex - such as the strategies between males to be the one that is selected.
preferred strategy of the male - quantity over quality.
competition between males to be able to mate with a female. winner reproduces and passes on characteristics to offspring.
given rise to dimorphism - obvious differences between the sexes. e.g. in physical competition between males, size matters - larger more likely to mate. females don’t compete, no evolutionary drive for larger females.
outline a psychological consequence of intra sexual selection.
for males to acquire fertile females and protect them from other males, may benefit from acting aggressively and thinking certain ways.
outline a behavioural consequence of intra sexual selection.
anisogamy states males optimum strategy is to mate with as many females as possible - due to minimum energy required and lack of post coital responsibility.
leads to a distinct preference for youth and a sensitivity to indicators of youth (e.g. certain facial features) and fertility (e.g. certain body shape).
discuss research support for preferences related to anisogamy as a strength of the evolutionary explanation.
one strength of ET is evidence from research support for preferences related to anisogamy.
Buss (1989) carried out a survey of over 10,000 adults in 33 countries. he asked questions relating to age and attributes that evolutionary theory predicts should be important in partner preference.
he found that female respondents placed greater value on resource related characteristics - e.g. good financial prospects. males valued reproductive capacity in terms of good looks and chastity, and preferred younger mates more than females did.
reflect sex differences in mate preferences due to anisogamy, and support predictions about preferences made my ET, giving the theory value.
ADDITIONALLY -
findings can be applied across vastly different cultures due to the large sample size - reflecting fundamental human preferences which are not primarily dependent upon cultural influences.
this suggests that the findings are not subject to culture bias, thus increasing the validity of the findings and increasing the support they can give the ET.
discuss research support for inter-sexual selection as a strength of the evolutionary explanation.
one strength of ET is evidence from research support for inter-sexual selection as a strength of the evolutionary explanation.
Clark and Hatfield (1989) showed that female choosiness is a reality of heterosexual relationships.
male and female psych students were sent out across a uni campus. they approached other students and asked ‘i have been noticing you around campus. would you go to bed with me tonight?’.
no females agreed to the request, whereas 75% of males did immediately.
this supports ET because it suggests that females are choosier than males when it comes to selecting partners.
discuss ET ignoring social and cultural influences as a limitation of the theory.
partner preferences over the past century have been influenced by rapidly changing social norms of sexual behaviour. these develop faster than evolutionary timescales imply and instead come due to cultural factors e.g. availability of contraception.
women’s greater role in the workplace means that they no longer require men to provide for them. researchers have argued that this social change has consequences for women’s mate preferences, which are no longer resource orientated.
Chang et al. compared partner preferences over 25 years and found some had changed and others had not, corresponding with huge social changes at the time.
this shows that mate preferences are the outcome of a combination of evolutionary and cultural influences. any theory that fails to take both into account is a limited explanation. thus, limiting the value of the ET.
