Evolutionary theory of relationships Flashcards
p118-119: Sexual selection and human reproductive behaviour
What are the two aspects of the evolutionary theory?
Sexual selection and human reproductive behaviour.
What is anisogamy?
The term ‘anisogamy’ is used to refer to the differences between male and female gametes (sex cells).
What are the two types of sexual selection?
Inter-sexual selection and intra-sexual selection.
What is the preferred sexual selection strategy of males and females?
Males prefer using intra-sexual selection (quantity over quality) while females prefer inter-sexual selection (quality over quantity).
According to Trivers (1972), why is it beneficial for females to use inter-sexual selection?
Trivers (1972) states that, because females invest more time and energy into the birth of their offspring, they stand more to lose in selecting the wrong partner.
What is the ‘runaway process’ in sexual selection? Give an example of this.
The ‘runaway process’ is the term used when a desirable trait is passed on due to it being selected, which results in these desirable genes being present in the offspring and taking up a larger percentage of the population. An example of this is the ‘sexy sons hypothesis’, devised by Fisher (1930), where ‘sexy’ traits are selected, and passed on and adopted by the offspring, which results in them having ‘sexy’ traits and the process repeats.
Describe intra-sexual selection.
The intra-sexual selection describes the competition between males for mating rights, where males with desirable traits are more likely to be selected and thus reproduce
Describe inter-sexual selection.
Inter-sexual selection describes when one gender makes mate choices based on characteristics of the other gender - in humans this is the females choosing the males
Briefly discuss supporting research into anisogamy.
Buss (1989) carried out a survey on over 10,000 adults from 33 countries and found females placed greater value on resource-related characteristics while males placed greater value on youth and beauty. This supports predictions of sexual selection theory due to anisogamy.
Due to a large and cross-cultural sample, this support has strong population and cultural validity; however, it only looked into heterosexual people and thus cannot be generalised to homosexual or bisexual people. Also being a survey means that it may have leading questions, reducing its validity, or alternatively it could reduce researcher bias as the researcher is not making assumptions on behalf of the participant.
Briefly discuss supporting research into inter-sexual selection.
Clark and Hatfield’s (1989) study on university students found evidence of female choosiness. Male and female students approached other students and asked them if they would like to have sex; 75% of males agreed to the request while 0% of females did. This is evidence of showing inter-sexual selection in females.
However, the study lacks population bias as it was only conducted on university students, and it also doesn’t take into account personal reasons (i.e. religion, sexuality, they might already be in a relationship) and so can’t be applied to homosexual people. It does have a degree of ecological validity though as it was conducted in the ‘field’ and is less likely to be affected by demand characteristics.
