Relationships Revision Notes
Evolutionary Explanations for Partner Preferences
Sexual Selection:
• Darwin’s (1871) concept of sexual selection concerns the selection of those
characteristics that aid successful reproduction (rather than survival).
• Physical characteristics, such as male peacock’s tail, are a sign of genetic fitness.
Females who select males with such characteristics are more likely to produce robust
offspring and therefore the preference for such a tail is perpetuated in future
generations.
• Other characteristics, such as aggressiveness, are adaptive because they provide an
advantage for a male over competitors for reproductive rights. The aggressive
characteristics that allowed the animal to reproduce in the first place are passed on
to offspring if they are genetically determined and remains in the population.
Anisogamy:
• The basis of human reproductive behaviour is anisogamy which refers to the
differences, between male and female sex cells (gametes).
• Male gametes (sperm) are small, highly mobile, created in vast numbers continuously
and do not need much energy to be produced.
• In contrast, female gametes (eggs) are relatively large, static, produced at intervals
for a limited number of fertile years and require a significant investment of energy.
• One consequence of anisogamy is that there is no shortage of fertile males, but a
fertile female is a much rarer ‘resource’.
• Anisogamy is important in partner preference because it gives rise to two types of
sexual selection.
,Inter-Sexual Selection:
• Inter-sexual selection is between the sexes - the strategies that males use to select
females or females use to select males.
• Inter-sexual selection is the preferred strategy of the female, quality over quantity.
• Trivers (1972) pointed out that the female makes a greater investment of time
commitment and other resources before, during and after the birth of her offspring.
• The consequences of making a wrong partner choice are more serious for the female, so
it pays for her to be especially selective. Therefore, the female's optimum mating strategy
is to select a genetically fit partner who is able to provide resources.
• It is this female preference which determines which features are passed on to the
offspring, e.g. if height is considered an attractive male trait by females, then it would
increase in the male population over successive generations.
• This is because, in each generation, females will select the tallest males and that
characteristic gradually becomes exaggerated (a runaway process).
• Fisher (1930) developed a ‘sexy sons hypothesis’. A female who mates with a male who
has a certain characteristic then will have sons who inherit this 'sexy' trait. Then her sons
are more likely to be selected by successive generations of females who will mate with
her offspring. Therefore the preference for this sexy trait is perpetuated.
Intra-Sexual Selection:
• Intra-sexual selection is within each sex - such as the strategies between males to be the
one that is selected.
• It is the preferred strategy of the male, quantity over quality.
• There is competition between males to be selected to mate with a female. The winner of
the competition reproduces and therefore the characteristics may be passed on to his
offspring.
• This strategy has given rise to dimorphism (‘two forms’) - males and females end up
looking very different because of intra-sexual selection; e.g. in any physical competition
between males, size matters.
• Larger males have an advantage and are therefore more likely to be reproductively
successful. On the other hand, females youthfulness is selected because males have a
preference to mate with younger more fertile women (large waist-to-hip ratio).
• Intra-sexual selection also has behavioural consequences. The characteristics that are
passed on allow a male to outcompete his rivals, including deceitfulness, intelligence and
aggression. E.g. males may benefit from behaving aggressively in order to acquire fertile
females and protect them from competing males. This leads to the selection of
aggressiveness in males.
,Evaluation:
Research Support for Inter-Sexual Selection
• Strength is evidence supporting the specific role of female choosiness in heterosexual
partner preference.
• Clark and Hatfield (1989) sent male and female psychology students out across a
university campus.
• They approached students individually questioning, “I have been noticing you around
campus. I find you to be very attractive. Would you go to bed with me tonight?”
• Not one female student agreed to the request – 75% of males immediately did.
• Supports the view that females are choosier than males when it comes to selecting
sexual partners and that males have evolved a different strategy to ensure reproductive
success.
Counterpoint – Complex View of Evolutionary Pressures
• The argument from sexual selection that one strategy is adaptive for all males, and
another is adaptive for all females is simplistic.
• It appears that strategies differ according to the length of the relationship.
• Sexual strategies theory (Buss and Schmitt 2016) argues that both males and females
adopt similar mating strategies when seeking long-term relationships. Both sexes are
very choosy and look for partners who are loving, loyal and kind.
• This is a more complex and nuanced view of how evolutionary pressures influence
partner preferences which takes account of the context of reproductive behaviour.
Sexual Selection and Homosexuality
• A criticism of sexual selection theory is that it cannot explain the partner preferences of
gay men and lesbian women. This is because in homosexual relationships partners are
not assessing genetic fitness.
• Lawson et al. (2014) looked at ‘personal ads’ placed by heterosexual and homosexual
men and women (describing what they looked for in a partner).
• They found that the preferences of homosexual men and women differ just as they do in
heterosexual men and women.
, Research Support for Intra-Sexual Selection
• Strength is evidence to support the predictions of sexual selection theory.
• Buss (1989) carried out a survey of over 10,000 adults in 33 countries.
• He asked questions relating to a variety of attributes that evolutionary theory
predicts are important in partner preference.
• He found that females placed greater value on resource-related characteristics than
males did, such as good financial prospects and ambition. Males valued physical
attractiveness and youth (signs of good reproductive capacity) more than females
did.
• Findings reflect consistent sex differences in partner preferences and support the
predictions from sexual selection theory.
Social and Cultural Influences Underestimated
• Limitation is that evolutionary theories overlook the influences of social and cultural
factors on partner preference.
• Partner preferences over the past century have been influenced by rapidly changing
social norms of behaviour. These develop much faster and have come about due to
cultural factors (e.g. availability of contraception).
• Women's greater role in the workplace means they are no longer dependent on men
to provide for them.
• Bereczkei et al. (1997) argue that this social change has consequences for women's
mate preferences, which may no longer be resource-oriented.
• Therefore, partner preferences today are likely to be the outcome of a combination
of evolutionary and cultural influences. Any theory that fails to account for bath is a
limited explanation.
Evolutionary Explanations for Partner Preferences
Sexual Selection:
• Darwin’s (1871) concept of sexual selection concerns the selection of those
characteristics that aid successful reproduction (rather than survival).
• Physical characteristics, such as male peacock’s tail, are a sign of genetic fitness.
Females who select males with such characteristics are more likely to produce robust
offspring and therefore the preference for such a tail is perpetuated in future
generations.
• Other characteristics, such as aggressiveness, are adaptive because they provide an
advantage for a male over competitors for reproductive rights. The aggressive
characteristics that allowed the animal to reproduce in the first place are passed on
to offspring if they are genetically determined and remains in the population.
Anisogamy:
• The basis of human reproductive behaviour is anisogamy which refers to the
differences, between male and female sex cells (gametes).
• Male gametes (sperm) are small, highly mobile, created in vast numbers continuously
and do not need much energy to be produced.
• In contrast, female gametes (eggs) are relatively large, static, produced at intervals
for a limited number of fertile years and require a significant investment of energy.
• One consequence of anisogamy is that there is no shortage of fertile males, but a
fertile female is a much rarer ‘resource’.
• Anisogamy is important in partner preference because it gives rise to two types of
sexual selection.
,Inter-Sexual Selection:
• Inter-sexual selection is between the sexes - the strategies that males use to select
females or females use to select males.
• Inter-sexual selection is the preferred strategy of the female, quality over quantity.
• Trivers (1972) pointed out that the female makes a greater investment of time
commitment and other resources before, during and after the birth of her offspring.
• The consequences of making a wrong partner choice are more serious for the female, so
it pays for her to be especially selective. Therefore, the female's optimum mating strategy
is to select a genetically fit partner who is able to provide resources.
• It is this female preference which determines which features are passed on to the
offspring, e.g. if height is considered an attractive male trait by females, then it would
increase in the male population over successive generations.
• This is because, in each generation, females will select the tallest males and that
characteristic gradually becomes exaggerated (a runaway process).
• Fisher (1930) developed a ‘sexy sons hypothesis’. A female who mates with a male who
has a certain characteristic then will have sons who inherit this 'sexy' trait. Then her sons
are more likely to be selected by successive generations of females who will mate with
her offspring. Therefore the preference for this sexy trait is perpetuated.
Intra-Sexual Selection:
• Intra-sexual selection is within each sex - such as the strategies between males to be the
one that is selected.
• It is the preferred strategy of the male, quantity over quality.
• There is competition between males to be selected to mate with a female. The winner of
the competition reproduces and therefore the characteristics may be passed on to his
offspring.
• This strategy has given rise to dimorphism (‘two forms’) - males and females end up
looking very different because of intra-sexual selection; e.g. in any physical competition
between males, size matters.
• Larger males have an advantage and are therefore more likely to be reproductively
successful. On the other hand, females youthfulness is selected because males have a
preference to mate with younger more fertile women (large waist-to-hip ratio).
• Intra-sexual selection also has behavioural consequences. The characteristics that are
passed on allow a male to outcompete his rivals, including deceitfulness, intelligence and
aggression. E.g. males may benefit from behaving aggressively in order to acquire fertile
females and protect them from competing males. This leads to the selection of
aggressiveness in males.
,Evaluation:
Research Support for Inter-Sexual Selection
• Strength is evidence supporting the specific role of female choosiness in heterosexual
partner preference.
• Clark and Hatfield (1989) sent male and female psychology students out across a
university campus.
• They approached students individually questioning, “I have been noticing you around
campus. I find you to be very attractive. Would you go to bed with me tonight?”
• Not one female student agreed to the request – 75% of males immediately did.
• Supports the view that females are choosier than males when it comes to selecting
sexual partners and that males have evolved a different strategy to ensure reproductive
success.
Counterpoint – Complex View of Evolutionary Pressures
• The argument from sexual selection that one strategy is adaptive for all males, and
another is adaptive for all females is simplistic.
• It appears that strategies differ according to the length of the relationship.
• Sexual strategies theory (Buss and Schmitt 2016) argues that both males and females
adopt similar mating strategies when seeking long-term relationships. Both sexes are
very choosy and look for partners who are loving, loyal and kind.
• This is a more complex and nuanced view of how evolutionary pressures influence
partner preferences which takes account of the context of reproductive behaviour.
Sexual Selection and Homosexuality
• A criticism of sexual selection theory is that it cannot explain the partner preferences of
gay men and lesbian women. This is because in homosexual relationships partners are
not assessing genetic fitness.
• Lawson et al. (2014) looked at ‘personal ads’ placed by heterosexual and homosexual
men and women (describing what they looked for in a partner).
• They found that the preferences of homosexual men and women differ just as they do in
heterosexual men and women.
, Research Support for Intra-Sexual Selection
• Strength is evidence to support the predictions of sexual selection theory.
• Buss (1989) carried out a survey of over 10,000 adults in 33 countries.
• He asked questions relating to a variety of attributes that evolutionary theory
predicts are important in partner preference.
• He found that females placed greater value on resource-related characteristics than
males did, such as good financial prospects and ambition. Males valued physical
attractiveness and youth (signs of good reproductive capacity) more than females
did.
• Findings reflect consistent sex differences in partner preferences and support the
predictions from sexual selection theory.
Social and Cultural Influences Underestimated
• Limitation is that evolutionary theories overlook the influences of social and cultural
factors on partner preference.
• Partner preferences over the past century have been influenced by rapidly changing
social norms of behaviour. These develop much faster and have come about due to
cultural factors (e.g. availability of contraception).
• Women's greater role in the workplace means they are no longer dependent on men
to provide for them.
• Bereczkei et al. (1997) argue that this social change has consequences for women's
mate preferences, which may no longer be resource-oriented.
• Therefore, partner preferences today are likely to be the outcome of a combination
of evolutionary and cultural influences. Any theory that fails to account for bath is a
limited explanation.
