Sexual Selection and Human Reproductive Behaviour

• Sexual selection is an evolutionary explanation of partner preference. Attributes or behaviours that increase reproductive success are passed on and may become exaggerated over future generations.
• Anisogamy refers to the differences between male and female sex cells. These are obvious in humans. Male gametes are extremely small, highly mobile, created in vast amounts and do not require a large expenditure of energy to produce.
• Female gametes are relatively large, static and produced at intervals for a fixed period of fertile years.
• A consequence of anisogamy for mate selection is that there is no shortage for fertile males but a fertile woman is a rare resource.
• Anisogamy is also important because it leads to two mating strategies or types of sexual selection.
• Intersexual selection is the preferred strategy of the female- quality over quantity. The female makes a greater investment of time , commitment and resources before, during and after birth. The consequences of making the wrong choice are much worse for a female.
• Therefore, the females optimum mating strategy is to select a genetically fit partner who is willing and able to provide resources. This leaves males to compete with the opportunity to mate with the fertile female.
• If height is considered an attractive trait then over successive generations of females, it would increase in the male population and daughters would have a greater preference for tall men.
• Fisher's sexy son hypothesis suggests a female mates with a male with a desirable characteristic, this trait is inherited by her son which increases the likelihood that successive generations will mate with her offspring.
• Intrasexual selection is the preferred strategy of the male - quantity over quality. It refers to the competition between males to be able to get with a female.
• The result of intrasexual selection is dimorphism which refers to the obvious differences between genders for example the importance of size in selection of males. Females don't have to compete for reproductive rights so there is no evolutionary drive favouring larger females.
• Intrasexual selection has behavioural consequences. Historically, for males to acquire fertile females and protect them from competing males, they may benefit from acting aggressively which may increase the likelihood of that trait.
• Anisogamy dictates that the male mating strategy is to mate with as many people as possible because of the minimal energy required for men to produce sperm and relative lack of post coital responsibility.
• A behavioural consequence of intrasexual competition is a man's preference for youth and fertility such as a specific body shape.