evolutionary theory of relationships

• Sexual selection

  Explains why certain seemingly disadvantageous characteristics (from an evolutionary point of view) are still passed on
• Sexual selection

  • These characteristics may be advantageous for sexual selection, such as males who behave aggressively (and so have a greater chance of protecting their female from competing males) and females with characteristic traits of fertility (such as a narrow waist and large hips)
• Heredity


  The process that determines which genes are passed onto offspring
• Anisogamy


  Differences between male and female gametes
• Differences in gametes

  • Size
  • Energy invested into their production
  • Whether they are static or mobile
  • Intervals at which they are produced
• Inter-sexual selection


  The strategies that each sex uses to attract the other
• Intra-sexual selection


  The strategies used within sexes to attract males
• Inter-sexual selection

  Favoured by females because they invest more energy into the development of ova, which are produced in limited numbers at intervals across their lives, and the fact that females experience more post-coital responsibility compared to males
• Intra-sexual selection

  Favoured by males because they produce sperm continuously throughout their lifetime, with little energy investment and limited post-coital responsibility
• Intra-sexual selection strategies

  • Males behaving aggressively and being protective of their female
  • Being larger (and so more sexually desirable to women)
  • Possessing certain facial and physical characteristics (e.g. strong jawlines and broad shoulders)
• Dimorphism


  The physical differences between the male and female sexes
• It is incorrect to assume that current reproductive patterns still have a strong evolutionary basis, but rather an interactionist approach would be more accurate, where the influences of both culture and evolution are combined together
• Changing social and cultural norms means that women no longer place a large emphasis on resource-availability when looking for a new partner, as they are now more financially independent, with the average age of marriage currently exceeding 30
• Some evolutionary pressures for inter-sexual selection no longer apply in the modern climate
• Research has suggested that there are some sexual selection pressures which have been constant in terms of evolution and in terms of modern times, such as the hip to waist ratio
• If the hip to waist ratio is around 0.7, then this demonstrates to potential mates that the female is fertile and able to carry children over a long period of time, with birth being easier when the female has larger hips and a narrower waist
• Females are more selective when it comes to potential mates, due to their greater energy and genetic input into the pregnancy and care for the child
• 75% of college males, compared to 0% of females, would be willing to sleep with a stranger if this stranger had approached them and complimented them
• This supports the idea that men have an evolutionary predisposition to want to impregnate as many women as possible, due to the high rates of sperm production and little energy/resources required to do so