PSYA3 Relationships - Parental Investment Theory

Evolutionary explanations of Human Reproductive Behaviour

Parental Investment Theory AO1

- Trivers (1972) defined ‘parental investment’ as being the investment a parent makes in an individual offspring, that increases that individual’s chances of surviving at the cost of the parent’s ability to invest in other offspring

- men’s minimum obligatory investment considerably less that womens

- Discrepancy has consequences for the reproductive strategies used by males and females (e.g. whether orientated towards short term or long term mating)

Maternal Investment
- Certainty of maternity: unlike males, females can be 100% sure they are the true parent

- Infant dependence on mother: a gradual increase in brain size over the past 2million years = childbirth more difficult. To compensate for difficulty, childbirth occurs earlier than is ideal so humans are born more immature than other mammals. As a result humans dependent on mothers until teenage years

Paternal Investment
- Danger of Cuckoldry: males can never be certain that offspring produced is theirs. Therefore they run the risk of using up valuable resources looking after another man’s offspring (cuckoldry)

Sexual/Emotional Jealousy
Possibility of sexual infidelity posed different adaptive problems for males and females
Males – unfaithful mate means risk of investing other men’s offspring (sexual)
Females –…