1. Relationships
Parental Investment

2. Quiz What is intrasexual selection? [2]
What is intersexual selection? [2]
What are males’ short-term mating preferences? [2]
What are females’ long-term mating preferences? [2]
How does the Buss (1989) study support the link between human reproductive behaviour and sexual selection? [4]

3. Starter How do females invest in their offspring?
How do males invest in their offspring?

4. Learning Objectives
To develop an understanding of the differences between male and female investment in their offspring.
Success Criteria
Complete page 21 of your booklet about differences in parental investment.
Evaluate sex differences in parental investment on page 22.
Mark and provide feedback on a sample essay.
Watch ‘Maury Povich’ and analyse for parental investment.

5. Males
Females

6. Trivers (1972)
Defined parental investment as “any investment by a parent in an offspring that increases the chance that the offspring will survive at the expense of that parent’s ability to invest in any other offspring (alive or yet to be born)”

7. Q1. Parental Certainty
Parental certainty is a measure of how certain a parent is that the offspring is their own.
How might this effect males more than females?
How might this influence parental investment?

8. Why do men and women invest differently in their offspring?
Women invest more in their offspring due to a limited number of eggs that they produce over a lifetime. Men can be far less choosy as they have a potentially unlimited number of children that could be fathered.
Women go for quality in men!
Men go for quantity of women!
As a result parents have to invest in their offspring so that all survive, sometimes investing in more vulnerable offspring as the stronger cope alone…this can cause conflict.

9. Q2. Maternal Investment WHY do females invest more?=
According to Daly and Wilson (1978) it is because men place so much effort into courtship and can opt out of parenthood; this cannot be the case for females.

10. Q3. Costs of maternal investment
Minimum of 9 months pregnancy followed by years of feeding and carrying.
Random mating is too costly for females.

11. Q4. What do males invest in their offspring?
Minimum is a few moments of copulation and teaspoonful of semen (Symons, 1979)
How does this influence indiscriminate mating?

12. Q5. The risks of paternal investment
Miller (1998)
Males more than females are worried about fidelity – there is the risk of cuckoldry (investment in someone else’s offspring).
There are also laws which make adultery an offence in terms of women rather than men!

13. Q6. Sexual Jealousy
Males and females behave differently when it comes to sexual jealousy:
When a male is unfaithful resources could end up being shared
When a female is unfaithful a man puts his resources into someone else’s offspring
Buss (1995) found men are more jealous of a sexual act (cuckoldry), women are more jealous of a shift in emotional focus (loss of resources).

14. Evaluation
Complete the evaluation questions on page of your booklets...don’t forget the synoptic information!!

15.  Baker and Bellis (1990)
A magazine survey of 2700 women was conducted.
It was estimated that 14% of the population is born as a result of extramarital affairs.
This links with evolutionary psychology – so that their efforts are not wasted women marry a man with resources and have an affair with a ‘stud’ (an attractive man with no resources).

16.  Benefits of cuckoldry
Additional support for their offspring (i.e. social support from another male) and perhaps better genes for her children.
The risks are abandonment from her partner or ‘male-retention strategies’ (threats or violence to her or the other male).

17.  Dunbar (1995)
Suggests that males restrict their reproductive opportunities and invest more in individual offspring as this is more desirable due to high costs of successful reproduction.
This criticise parental investment because it shows men have free will and are not interested in unlimited offspring like evolutionary theory suggests.

18.  Rowe (2002)
Rowe criticises the evolutionary theory because he says that men’s behaviour is affected by social and personal conditions too (e.g. quality of the relationship with the mother, characteristics of the child, or the personality of the father).
This shows that the evolutionary perspective is reductionist and does not take into account all factors when parental investment is considered.

19. Anderson (1999) Parental certainty is not always an issue for males.
Anderson measured parental investment from fathers and stepfathers (time spent with child and financial investment).
It was found that men did not discriminate between children born in the current relationship or by a previous partner.
This criticises parental investment as you would not expect men to invest in a child that was not their own.

20. Buss et al. (1992)
Male US students were found to be more jealous of sexual infidelity.
Linking with the idea of cuckoldry.
Female US students were found to be more jealous of emotional infidelity.
Linking with the idea of extramarital affairs and loss of resources.

21. Michalski and Shackelford (2005)
In terms of investment:
Maternal grandmothers invest the most.
Maternal grandfathers.
Paternal grandmothers.
Paternal grandfathers.
Think about this in terms of parental certainty...mum’s mum is certain you are her grandchild. Dad’s dad is definitely not sure!!

22. Essay Task You will be given an essay all jumbled up
Rearrange the essay into the correct order
Stick it on the A3 sheet
Mark on the AO1, AO2 and AO3
Give the essay a mark out of 24
Give the author some feedback on how to improve using the mark scheme

23. Plenary http://www.youtube.com/watch?v=Vgsdl-qTVgw

24. Create an essay plan for the following question: ‘Discuss sex differences in parental investment.’ [24 Marks]
Paragraph 1
Paragraph 2
Paragraph 3
Paragraph 4
Paragraph 5
Paragraph 6

25. Learning Objectives
To develop an understanding of the differences between male and female investment in their offspring.
Success Criteria
Complete page 21 of your booklet about differences in parental investment.
Evaluate sex differences in parental investment on page 22.
Mark and provide feedback on a sample essay.
Watch ‘Maury Povich’ and analyse for parental investment.