Discuss the role of sexual selection in human reproduction

Sexual Selection
Sexual selection is the process whereby individuals advertise both their own requirements in a mate and their own attractive characteristics as a mate. Selection involves attracting the mate with the greatest fitness whilst at the same time maximising the chances of being selected as 'fit' themselves. Fitness in the context of evolution theory refers to the ability to reproduce and leave offspring. How animals select their mate is crucial to the species as it has a direct effect on the gene structure within their populations, and an effect on the future of the entire gene pool. There are two types of sexual selection. Intra-sexual selection refers to competition for reproductive success between members of the same sex - for instance males competing with other males for reproductive opportunities. An example of this is the way in which male stags fight over females. Inter-sexual selection refers to selection by females choosing from the available pool of male mates on the basis of features which they find desirable. For example, a female stickleback will choose a male to fertilise her eggs on the basis of how beautiful the nest that he has created.
Ridley says that in the past 100,000 years the human species has hardly evolved, therefore our psychology is similar to when we were hunter gatherers. This means that males have to find ways to ensure their reproductive success, and a way to attract females is to show that they have the right characteristics and traits. Some examples of characteristics are wealth, intelligence and strength. This have been supported by a study conducted into mate preferences by Buss (1989). Buss explored what males and females looked for in a marriage partner. The study involved over 10,000 participants from 37 different cultures. These results showed that women more than men desired mates who were ‘good financial prospects’. Also, this shows evidence of intrasexual selection (male competition). It is also thought that women are driven to secure the best genes possible, and want to be protected by a powerful man so their children have the highest chance of surviving.
Studies such as Buss’s survey of mate choice might suffer from a serious problem of validity – i.e. they give us an indication of expressed preferences rather being a reflection of what actually happens in real life. . For example, people may express a preference for an ideal partner (intelligent, kind etc.) but may have to settle for less. However, many real-life studies also support these mate-choice hypothesis. For example, a study of actual marriages in 29 cultures (Buss. 1989) confirmed that men do choose younger women (which was also a result from the mate choice survey). Conversely, Kenrick et al 1996 rejected this hypothesis and found that teenage males are most attracted to women who are five years older than them, despite the fact that such women usually show no interest in them, and are vertianly not more easily controlled by adolescence males.
Furthermore, it is also suggested that female mate choice varies across the menstrual cycles. Penton-Voak (1999) found that women chose a slightly feminised version of a male face as ‘most attractive’ for a long-term relationship. However, for a short-term sexual relationship, during the high conception risk phase of the menatrual cycle, the preferred face shape was more masculinised. The theory of sexual selection may well have favoured females who pursue a mixed mating strategy under certain conditions. A female might choose a main partner whose feminised appearance suggests kindness and cooperation in parental care, but might also copulate with a male with a more masculine appearance when conception is most likely. Such males are likely to have higher levels of the hormone testosterone (which suppresses the immune system). A male who is healthy despite this must, therefore, have a highly efficient immune system – a very valuable characteristic to pass on to offspring- which increases their ‘attractiveness’. Although research consistently reports than men more than women have a desire for a variety of sexual partners and a greater willingness for casual sex (evidence for sex differences in short term mating preferences comes from a study by Clarke and hatfield 1989 as an example), men could never have evolved this desire in the absence of willing females. Despite that fact that short-term mating carries a considerable potential cost to the women, there must also be some benefits. Greiling and Buss 2000 suggest that she could profit in a number of ways, including using short-term mating as a way of leaving a poor-quality relationship or as a way of more genetically diverse offspring. As a result, explanations that emphasise the advantages of short-term mating only to males, offer a gender biased view of mating behaviour.
Also, some psychologists argue that the relevance of evolutionary factors has been overemphasised, this is not how people really live and choose partners and decisions are more likely to be made on a whole range of issues and suggest that evolutionary influences on human reproductive behaviour are lost in today’s social context. This therefore suggests that evolutionary explanations are reductionist as they are too simplistic and focus on innate instincts and ignore another other important factors such as social, cognitive or environmental variables. Additionally, this theory could be said to have low historical validity as these ‘trends’ haven’t necessarily been demonstrated within society (past and present).