9.1.1

Sexual Selection & Human Reproductive Behaviour

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Sexual Selection

Sexual selection is a special case of natural selection.

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Intersexual selection

  • Sexual selection is where members of one biological sex choose mates of the other sex for reproduction.
  • This is known as intersexual selection.
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Intrasexual selection

  • It can also refer to members of the same sex competing for access to members of the opposite sex.
  • This is known intrasexual selection.
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Reproductive advantage

  • Sexual selection explains why some characteristics often seem disadvantageous but actually give a reproductive advantage.

Anisogamy

Anisogamy refers to the differences between male and female sex cells (or gametes).

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Gametes

  • Gametes are very obvious in humans and non-human animals but differ significantly between male and females.
  • Male gametes (sperm) are extremely small and highly mobile.
  • Sperm is created continuously in vast numbers from puberty to old-age. Males don't have to expend a lot of energy to produce sperm.
  • Female gametes (eggs or ova) are relatively large and static.
  • Ova are produced at intervals for a limited number of fertile years.
  • Women use lots of energy producing ova.
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Consequences of Anisogamy

  • Anisogamy has many effects on mate selection, such as an abundance of fertile males but a much a smaller number of fertile females.
  • Anisogamy is also important in partner preference because it results in two different mating strategies, which in turn means there are two types of sexual selection: intersexual and intrasexual selection.
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Inter and intrasexual selection

  • Intersexual selection is the selection between the sexes, i.e. the strategies that males use to select females and females use to select males.
  • Intrasexual selection is competition within each sex, i.e. strategies between males to be the one that is selected.

Buss (1989) - Sex Differences

Buss (1989) studied the sex differences in mate strategies.

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Study explanation

  • Buss (1989) surveyed over 10,000 adults in 33 countries.
  • He asked them questions relating to age and a variety of attributes that evolutionary theory predicts should be important in partner preference.
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Study findings

  • Buss (1989) found that females placed a greater value on resource related characteristics, such as favourable financial prospects, ambition and industriousness.
  • Males valued reproductive capacity, such as good looks and chastity, and preferred younger mates more than females did.
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Study conclusions

  • These findings reflect sex differences in mate strategies.
  • This is partly because of anisogamy.
  • The findings support predictions about partner preference derived from sexual selection theory.
  • They can be applied across different cultures because they reflect fundamental human preferences not primarily dependent upon cultural influences.

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1Social Influence

2Memory

3Attachment

4Psychopathology

5Approaches in Psychology

6Biopsychology

7Research Methods

8Issues & Debates in Psychology (A2 only)

9Option 1: Relationships (A2 only)

10Option 1: Gender (A2 only)

11Option 1: Cognition & Development (A2 only)

12Option 2: Schizophrenia (A2 only)

13Option 2: Eating Behaviour (A2 only)

14Option 2: Stress (A2 only)

15Option 3: Aggression (A2 only)

16Option 3: Forensic Psychology (A2 only)

17Option 3: Addiction (A2 only)

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