evolutionary explanations: sexual selection in human reproductive behaviour Flashcards
natural selection
process by which inherited characteristics become more or less common in a population as they confer some environmental advantage that makes it more likely for an individual to survive
some of these become displays of health and fitness which demonstrate an individual’s increased likelihood of bearing strong offspring
sexual dimorphism > different characteristic evolve in males (e.g. strength) and females (breasts)
secondary sexual characteristics are then displayed by an individual in order for them to be selected by a mate through sexual selection
males display their ability to protect and provide whilst females display fertility to carry and care for children
sexual selection
display of desirable characteristics to increase one’s chance of securing a mate for reproduction
women predominately engage in inter-sexual selection, which is the act of selecting an ideal mate, men engage in intra-sexual selection (competition between men to be selected)
differences in selection and competition leads to differences in males and females when choosing a partner
women - sexual selection
have limited reproductive possibilities (one fertilised ovum per month for a short reproductive period)
so, women are biologically motivated to invest more in caring for their offspring and are motivated to carefully select an ideal mate (inter-sexual selection) to pass on their selfish genes (Dawkins)
especially true as can be certain their offspring is genetically theirs (travis, internal fertilisation theory) so are more likely to invest heavily in their children
so, women will seek signs of provision (high financial status) and signs of protection (muscular physique). they also tend to select an older partner as characteristics associated with provision are more likely in older males
in evolutionary past, only by being selective that women would get a mate who could best protect and provide for her and offspring in order to pass on their selfish genes
men - sexual selection
men have numerous reproductive possibilities (up to 300m sperm per ejaculation throughout adult life)
so, men are biologically motivated to invest less in caring for offspring and motivated to compete to be selected by numerous fertile mates (intra-sexual selection) to pass on selfish genes (Dawkins)
especially true as men cannot be certain their offspring in genetically theirs (Travis, Internal fertilisation theory) so are less motivated to invest heavily in children
so, men will seek general signs of youth (bright eyes, rosy cheeks) as well as specific signs of fertility (large breasts)
in evolutionary past, it was only by being promiscuous that men could best increase their chance of having offspring in order to pass on selfish genes
theories about evolutionary advantage of human reproductive behaviour
biological market place theory - Noe and Hammerstein (1995)
sexual strategies theory - Buss and Schmitt (1993)
long term courtship and mate guarding
advantageous to men as they enable them to retain access to one fertile woman
females - means the increased investment of resources by a man to her and children so, reduces chance of him later abandoning her and offspring
through mate guarding, couples monitor each other to ensure other potential partners know they are taken
important to men as they don’t want to waste their resources on raising a child that doesn’t share his selfish gene whilst women need to ensure their male uses all his resources on her and offspring and not spread it over multiple mates
one night stands and sneak copulation
advantageous to men as they enable them to increase their reproductive possibilities without having to heavily invest in a woman or her offspring
could mean that an offspring will have ones selfish gene but another man will use his resources to raise the child
women - provide access to a wider gene pool to maximise the chance of their offspring reaching sexual maturity and pass on her selfish gene
could allow for her to remain in a long term relationship with a resource rich but genetically poor mate but having offspring with a resource poor but genetically fit mate
sexy sons hypothesis
fisher (1930)
argues that females select desirable males as they know their sons will also share these desirable traits
increases likelihood they will reach sexual maturity and be found highly attractive themselves by future females
through this, a runaway process can occur where certain characteristics become fashionable over time
handicap hypothesis
zahavi (1975)
argues females select males with some disadvantage that shows his ability to thrive as this is a sign of his superior genes
may explain why some females find men attractive despite their socially undesirable behaviour
strength partner preferences
convincing evidence for role of sexual selection in partner preferences comes from
buss (1989)
in a cross-cultural study of 10,000 ppts across 33 countries found that, men sought physically attractive and younger women whilst women looked for a male’s financial capacity by seeking financial success or ambition
shows that due to women’s limited reproductive opportunities, they choose a partner that can provide for her and her offspring whilst men, due to their many reproductive opportunities, choose a partner whose youth and fertility will best lead to reproduction
strength human reproductive behaviour
evidence for role of sexual selection in human reproductive behaviour comes from
clarke and Hatfield 1989
used confederates to offer casual sex to men and women. 75% of males agreed to request yet none of the women did
shows that, as men compete to be selected by numerous female partners, they are more likely to agree to an opportunity to reproduce whereas women more carefully select an ideal mate and so are far less likely to agree
strength human reproductive behaviour 2
compelling research evidence from buss 1993
reported men would be more jealous due to infidelity, whereas women would be jealous if their partner formed an emotional bond to another woman
suggests sex differences in jealousy reflect the behaviour each sex shows in relationships: women seek a mate who can protect and provide for her and offspring and wouldn’t want this to be shared with another female
men seek a mate who will raise his offspring so would not want to risk investing in a child that may not be his
so, both sexes display mate guarding behaviours such as buying wedding rings to signify they are taken and in a long term relationship
strength partner preference 2
strong evidence from Buss and Schmitt (1993)
asked males and females how many sexual partners they would like in the future and found men sought 18 partners whilst women sought 5 in their lifetime
shows due to a mans many reproductive opportunities, best way to pass this selfish gene is by having numerous mates to increase offspring
however, due to a woman’s limited reproductive opportunities, the best way for her to pass her selfish gene is to choose a partner that can provide for her and offspring in the long term
strength of partner preference 3
strong evidence from Gross (2001) and Singh (1993)
found, across many cultures, women reported male shoulder to waist ratio of 0.85-0.9 (v-shape) was most attractive whereas men reported ratio of 0.7 (hour glass figure) was most attractive
shows men prefer partner who displays features which are most likely to increase chance of bearing a child (large breasts and child bearing hips) whilst women prefer a partner who displays their ability to protect and provide (muscular)
as this was found regardless of culture, it adds further evidence that these behaviours have evolved in humans rather than learnt
general strength
culturally universal
which is when a theory argues that behaviour is the same across all groups, including culture
this is because research suggests that characteristics in men and women that are seen as attractive are the same in all cultures e.g. Buss 1989 showed features such as signs of fertility (women) and offering protection (men) are universally attractive
meaning explanations account for human behaviour across the globe
