Discuss the relationship between sexual selection and human reproductive behaviour.
Reproductive success is at the very heart of the evolutionary process. Among early humans, those who failed to mate also failed to become ancestors. For our ancestors, successful mating was a complex business, involving selecting the right mate , out-competing rivals and then engaging in all the right behaviours for successful conception and child rearing. It follows then, that modern-day humans have a similarly complex collection of psychological adaptations specifically dedicated to the task of mating. Being choosy for a mate involves a lot of time, effort and energy. Sometimes the costs of mate choice can impair survival. The rationale behind sexual selection is that random mating is essentially stupid mating. It pays to be choosy, as the genetic quality of a mate will determine half the genetic quality of an offspring. Low quality mates will be more likely to produce unattractive, unhealthy offspring. By joining forces with an attractive, high-quality mate, offspring are higher quality and an individual’s genes are much more likely to be passed on.
An important feature of most sexually reproducing species is that males are more brightly coloured than their female counterparts; the classic example of this is the peacock’s tail. One would expect such disadvantageous traits not to be naturally selected – unless they and enhanced reproductive success in some way. Darwin (1874) came up with his theory of ‘sexual selection’. There are 2 processes. One of them is called intrasexual selection, also known as mate competition. This is when members of one sex compete with each other for access to members of the other sex. The victors are able to mate and so pass on their genes, whereas the loser’s do not. The other process is called intersexual selection, this is sometimes called mate choice. This form of selection involves the preferences of one sex for members of the opposite sex who possess certain qualities. For example, if all females preferred tall males, over times there would be an increase in tall males on the population. The preferences of one sex, therefore, determine the areas in which the other sex must compete.
Human beings possess a menu of different mating strategies, some of which evolved specifically for short-term mating success. According to the parental investment theory, men evolved a greater desire for casual sex, and would ideally seek sex earlier in a relationship. Female behaviour would not be subjected to the same evolutionary pressures. Over the period of one year, for example, a male who managed to impregnate a large number of female would have passed on more copies of his genes than a less successful male. On the other hand, a female who had sex with the same amount of people would only be able to get pregnant once in that 9 month period. Although research consistently reports that men more than women have a desire for a variety of sexual partners and a greater willingness for casual sex…