In sexual selection members of one sex (usually males) compete with each other for access to members of the other sex. Victors are then able to mate and so they can then pass on their genes, whereas the losers do not. Whatever traits lead to success in these same-sex contests will be passed onto the next generation. This is called Intrasexual Selection (mate competition.) Intersexual selection (mate choice) involves the preferences of one sex for members of the opposite sex who possess certain qualities. For example if women prefer tall men, over time there would be an increase in tall men in the population, as the gene for tall men would keep being passed on. The preferences of one sex will determine the areas in which the other sex must compete. Indicators given will reveal traits that could be passed onto any offspring, (i.e. selection for good genes) as well as any information about the chances of the mate being able to give protection and support to the offspring, (i.e. the selection for good parents).
Human beings are pre-programmed to attend to displays of these indicators, which in turn increases their willingness to mate with the individual who possesses them.
Another part of the nature of sexual selection is the short term mating preferences. Humans have a variety of different mating strategies; some of these have evolved specifically for short term mating success. According to the Parental investment theory, men have evolved a greater desire for casual sex, and would seek sex earlier in a relationship. This is an innate desire as a male who manages to impregnate a large number of females would have passed on more copies of their genes than a less successful male, whereas a female who has sex with the same number of men can only produce one child at a time. Buss 2007 said that the less time a man spends with a woman before they have sex the larger number of women he can impregnate in the given time.
Buss and Schmitt (1993) said that in contrast to men women lower their standards in the context of short term mating opportunities. Research consistently reports that men more than women have a desire for a variety of sexual partners and a greater willingness for casual sex, men could not have evolved this desire without the willingness of females. Despite the fact that short term mating carries potential costs to the woman there must be some benefits. Greiling and Buss (2000) suggests that a woman could profit by using short term mating as a way to leave poor-quality relationships, or as a way of producing more diverse offspring. This shows that there is gender bias in the research into short term mating preferences and that its not just men that have a desire for casual sex, and it leaves out any mention that it could work for both sexes.
In long term mating, both men and women invest heavily in any offspring. As a consequence of this, sexual selection should favour high levels of choosiness in both sexes. As women have an obligatory biological investment in their children, they are more particular about their choice of mate. This means that the type of mate they would go for would be someone who can protect her and the children and show strong promise as being a good parent. Men are more attracted to females who display strong signs of fertility. Buss found universal trends in male and female mating preferences. It is more logical to be choosy when deciding on a mate, even though it requires more time and energy. Random mating is essentially stupid mating. It pays to be choosy as the genetic quality of a mate will determine half of the genetic information of any offspring. This supports the nature of sexual selection as long term preferences need people to be choosy when deciding on a mate as they want the best genes possible.
Research by Penton-Voak (1999) suggests that female mate choice varies across the menstrual cycle. They found that women chose a slightly feminised version of a male face as ‘most attractive’ for a long term relationship. However for short term relationships, during the high conception risk phase of the cycle, the preferred face shape was more masculinised. This therefore shows the differences between short term and long term mating preferences in a relationship. In most mammalian species the female gives out a variety of visual or chemical signals, which encourage the male to mate. In human females it is hidden, but women near the most fertile point in their cycle are more attractive. A recent study showed this as the tips earned by lap dancers varied during different stages of their cycle.
One of the most striking conclusions from Buss’s study of 37 cultures was that men have a distinct preference for younger women. This finding was consistent with the theory of sexual selection because the younger the women are the more fertile they are. However some critics have tried to explain it in terms of power, as younger women are easier to control, therefore preferred as mates. Kenrick (1996) rejected this hypothesis. They found teenage males are more attracted to women who are five years older than them. This therefore shows that the research is inconclusive as the findings contradict each other so no conclusion can be drawn and the results can’t be generalised.