evolutionary explanations for partner choice

• Evolution

  Each living thing (organism) has a set of characteristics encoded by its genes.

  The organism inherits its genes from its parent(s)

  Variations between organisms are caused by variations in the genotype.
• Evolution requires the organism:

  To live to reproductive age

  To mate successfully

  To ensure the offspring’s survival
• Natural selection – survival of the fittest

  •Ability to survive in a particular environment (fitness)
• Sexual selection – survival of the sexiest

  •Ability to attract/find a mate and reproduce successfully.

  •Attributes and behaviors that increase reproductive success are passed on to future generations.
• Anisogamy is the difference between male and female sex cells.
• Male sex cells (sperm)

  •Plentiful and continuous production from puberty

  •Relatively ‘cheap’ to produce

  Female sex cells (egg)

  •Produced at intervals for a limited number of years

  •‘expensive’ to produce
• A consequence of anisogamy is that there are plenty fertile males but fertile females are a rarer ‘resource’.
• Inter-sexual selection is the selection of mates between sexes e.g. strategies females use to select males and vice versa.
• Female strategy: Quality over quantity

  Females make a greater investment of time, commitment etc. (before, during and after birth)

  Therefore, females optimum mating strategy is to select a genetically-fit partner who can provide resources
• Male strategy: Reproductive success

  Reproduction is not costly to males, therefore they aim to reproduce as many times as possible to pass on genes

  Therefore, they value youthfulness and a large hip-to-waist ratio(suggests fertility)
• Sexy sons hypothesis

  Preferences of both sexes determined attributes that are passed on.

  e.g. is height is seen as attractive in males, these males are the most likely to reproduce and pass on this gene, increasing the trait in the population.
• Intra-sexual selection is the selection of mates within sexes e.g. males compete with other males for mates
• male strategy: Quantity over quality

  Males compete for access to females as sperm is plentiful but fertile females are limited and choosey

  The winners pass on their traits to their offspring
• Dimorphism

  Competition has led to dimorphism (two forms) in males and females.

  In many species males have exaggerated characteristics to increase attractiveness and compete for the females
• Strength

  A review of lonely hearts adds (adverts in the paper looking for partners) found males tend to seek youthful females and females tend to seek professional/wealthy males.

  This supports the theory that males favour characteristics that suggest fertility and females favour characteristics which suggest they can be provided for, supporting the evolutionary theory of partner preference
• Strength

  In a study students asked other students ‘ I find you very attractive, would you go to bed with me tonight?”. No female student agreed, but 75% of males agreed.

  This supports the view that females are choosier than males in partner preference and that males have evolved a different strategy for reproductive success
• Weakness

  Buss claims sexual selection theory is simplistic as it suggests different strategies are used for different sexes, however argues both sexes have similar preferences when seeking long term partners.

  This contradicts the original evolutionary theory and propose a more complex theory which considers context.
• Weakness

  Partner preferences have been influenced by changing social norms and cultural practises e.g. the availability of contraception and changing workplace roles means partner preference is no longer resource oriented.

  Suggests partner preferences today are likely due to both evolutionary and cultural influences – a theory failing to explain both is limited