Conflict between natural and sexual selection

• There can be conflict between natural and sexual selection
• Traits giving a reproductive advantage, natural selection happens with traits that give a survival advantage, makes trait more likely to survive
• Attractive traits sometimes make a mate less likely to survive, sexual selection can conflict with natural selection more generally.

  i.e. Colourful male peacocks
• One theory from evolutionary psychology explaining why this happens is through handicap principle
• Zahavi (1975)

  • Argued displaying a noticeable handicap to survive indicates survival strength --> handicap principle
  • If an individual has managed to survive despite unhelpful characteristics they have superior genes
• Handicap principle applied to humans

  • Masculine features (i.e. strong jaw) result from high testosterone levels
  • Testosterone causes less responsive immune system meaning these features are costly for an individual
  • Features only displayed by those who can afford the handicap