Evolutionary explanation

• What is sexual selection?

  • Attributes or behaviours that increase reproductive success are passed on through genes, which depends on our chances of survival and our ability to attract a mate
  • Charles Darwin - females establish a preference for male characteristics that enhance reproductive success, putting males under pressure to improve that trait
  • Male goals are to outcompete their rivals, mate when it is ensured a child will be conceived, and ensure the child lives long enough to reproduce and pass their genes on
• What is human reproductive behaviour and the goal of this?

  • Any behaviours relating to the opportunities to reproduce and increase the survival chances of our genes
  • Main goal is to reproduce and pass on their genes
• What is anisogamy?What are the consequences of anisogamy?

  • The differences between male and female sex cells (gametes)
  • Female gametes (eggs) are larger in comparison, static, have limited years of fertility and invest a lot of time/energy into reproduction
  • Male gametes (sperm) are smaller, extremely mobile, have an infinite supply, and invest little time and energy into reproduction
  • Means fertile females are much rarer but there is no shortage of male mates
• What is intersexual selection?

  • Strategies that males and females use to select each other - females select a genetically fit partner willing to provide
  • Trivers: consequences of wrong partner choices are more serious for females (due to rare eggs) so invest greater time/commitment
  • Female's preference determines which features are passed onto the offspring e.g. height will increase in males over generations
  • Fisher: 'sexy sons' hypothesis - females mate with males that have reproductive characteristics, inherited by their sons who are then more likely to be selected by females to mate
• What is intrasexual selection?

  • Strategies within each sex to be the one that is selected
  • Competition between males to be selected by a female - winner reproduces passing on his victorious characteristics to offspring
  • Dimorphism: males and females look different e.g. size in men, young fertility in women (waist-to-hip ratio)
  • Behavioural consequences: men may act more aggressive to acquire fertile females and protect them from competing males, leading to selection of aggressive men
• What evidence supports the role of female choosiness in intrasexual selection?

  • Clark & Hatfield (1989): sent male and female students on a university campus to approach others saying they found them attractive, asking them to go to bed with them the same night
  • 75% of males agreed, 0% of females
  • Shows females are choosier than men when selecting sexual partners evolving different strategies to ensure reproductive success -> supporting Trivers (1972)
• What evidence supports intrasexual selection?

  • Buss (1989): surveyed 10k adults in 33 countries in attributes that the theory predicts to be important in partner preference
  • Females preferred resource-related, financial characteristics
  • Males value physical attractiveness and youth as signs of good reproductive capacity
  • Findings reflect consistent sex differences in partner preferences, supporting sexual selection theory
• Why can cultural differences be just as important as evolutionary forces in gender differences with mate preference?

  • Kasser and Sharma (1999): analysed 37 cultures and found that women value resource-related characteristics in mates MORE in the cultures where women's status and educational opportunities are limited
  • Weakens evolutionary explanation, underestimating the role of social and economic factors in establishing mate preference patterns
• Are female mate preferences for high-status men universal?

  • Buller (2005): majority of studies that attempt to determine female mate preferences were carried out on female undergrads
  • Their preference for high status men may just be a preference of men with similar interests or educational prospects to their own
  • Weakens evolutionary psychologists' claim that female preference for high status men is universal as this evidence is weak