Sexual selection is a process that favours individuals possessing features that make them attractive to members of the opposite sex or help them compete with members of the same sex for access to mates. Darwin believed that the competition between mates of the same sex affects the evolution of some physical characteristic. Such as, the famous peacocks’ tail, which demonstrates that males have a large attractive tail to attract mates of the opposite sex and to stand out from their rivals.
This led Buss and Workman and Reader to come up with two kinds of mate selection. One of them, called the Intrasexual which consists of individuals competing with members of their own sex for access to the opposite sex. This creates competition between the males as they fight each other in order to access the female. The second type of mate selection is known as intersexual, this consists of members of one sex attempting to impress members of the other. This is normally based on females, as they need to be impressed before they consent to mating.
This mating selection led to Fisher’s “runaway process” which consists of an adaptive feature used by females choosing a sexual mate; this may become exaggerated over many generations. Also, the “sexy sons hypothesis” states that females choose a sexual partner for successful and attractive attributes as they are likely to pass onto their sons; this leads to successful mating, therefore the females genes will be passed on and continued. However, this hypothesis has been criticised by Zahavi, suggesting that the exaggerated feature is regarded as handicap and not an asset (Handicap Theory).
However, evolutionary perspectives on human mate selection are extremely deterministic; Thornhill and Thornhill said that men who are unable to mate are driven to rape women. Trivers defines parental investment as ‘any investment by the parent in an individual offspring that increases the offspring’s chance of surviving at the cost of the parent’s ability to invest in other offspring’. Females investments tends to be far greater because female garnets are less numerous and more costly to produce compared to male garnets.
Humans tend to share the care of their offspring because of the high cost of successful reproduction. Males restrict their reproductive opportunities and invest more in each offspring. This means that male humans are quite choosy in their females; this could be why characteristics that indicate good genes are important in females. A study conducted by Buss in which he looked at 37 different cultures and found that females valued qualities that suggested the potential of males whereas men valued physical attractiveness and women who were younger than them.
This suggested that they were looking for qualities associated with fertility in line with evolutionary predictions. Evolutionary theory, however, can be reductionist as it ignores social, cultural and moral influences on our reproductive behaviour. It is also deterministic, because humans have the ability to think about their actions. Nevertheless, evolutionary theory can be very difficult to test experimentally.