A01 Sexual Selection And Human Reproductive Behaviour

• Sexual selection


  Explains why some characteristics that appear disadvantageous actualy confer an advantage to the human reproductive behaviour. Therefore, the characteristics are attractive to potential mates.
• Advantageous characterisitcs and competition

  They may provide advantages over competitors for reproduce rights ( greater height, facial and bodily features for example).
• Anisogamy

  Refers to a difference in gamete size in males and females.
• Male gametes

  Sperm is extremely small, highly mobile and created continiously in vast numbers from puberty to old age. Does not require a great expenditure of energy to produce.
• Female gametes

  Ova (eggs) are relativly large, static and produced at intervals for a limited number of fertile years. Requires huge investment of energy.
• Consequence for male selection of anisogamy

  There is no shortage of fertile males but fertile women are consdiered a 'rare resource'.
• Anisogamy's importance for partner preference

  Gives rise to two different mating strategies which in turn are two different types of sexual selection: Inter-sexual selection and intra-sexual selection.
• Inter-sexual selection


  Preffered strategy of females-quality over quantity. Ova is rarer than sperm and require greater energy.
• Trivers' theory (Inter-sexual selection)

  Emphasises females make a greater investment of time, commitment and reources befre, during and after birth. Both sexes are 'choosy' as they both stand to lose if they invest in a substandard partner so consequences of making wrong choice of partner is more serious for females than males so it pays for females to be more 'choosy'. Thus, females optimum mating strategy is to select a genetically fit partner who is able and willing to provide resources.
• Female preference and its consequences on offspring

  It is this female preference for a fit male which determines features passed on to the offspring. For example, if height was considered attractive, then that would increase in the male population as all the females would mate with tall males producing taller sons and daughter who have a preference for taller males.
• Fisher's 'sexy sons' hypothesis

  Fisher describes female preference and its consequences on offspring as a 'runaway process' where a female mates with a male who has a desirable characteristic and this 'sexy' trait is inherited by the sons.
• Intra-sexual selection

  Preffered strategy of males- quantity over quality. Refers to the male competition between males to be able to mate with females. Winner of the competition reproduces and gets to pass on the characteristic that contributed to his victory.
• Evolutionary drive


  This strategy has given a rise to dimorphism, an obvious difference between males and females. For example, the competition between males: size matters. But for females, they do not compete for reproductive rights so there is no evolutionary drive towards larger females.
• Psychological consequences of Intra-sexual selection

  Controversial as for males to acquire fertile females and compete with other males, they may benefit from aggressive behaviour and think a certain way. Anisogamy dictates males; optimum reproductive structure is to mate with as many fertile females as possible as the minimum amount of energy required to produce sperm allows to theoretically, fertilise every woman on earth and relative lack of post-coital responsibility the male carries.
• Behavioural consequences of Intra-sexual selection

  Behaviour consequences lead to a distinct preference for youth and sensitivity to indicators of youth as well as fertility.