Furthermore, Singh et al found men preferred waist to hip ratio of 0.7 across cultures. This is a typical hourglass figure and a sign of fertility which further supports the sexual selection theory.
In addition to this, Thornhill et al found that symmetrical faces were sought by both genders and that symmetry was a sign of strong genetic fitness and strong resistance supporting the sexual selection theory. Women also sought men with masculine features while men preferred women with childlike features such as large eyes, small nose, good teeth and full lips – these are all indicators of good fertility. Both genders engage in behaviours that increase reproductive success.
Evidence for sex differences in short term mating preferences comes from a study by Clarke and Hatfield. Men and women experimenters approached strangers on a college campus and told them they found them attractive. They then asked them one of three questions: 1. Would you go on a date with me? 2. Would you go back to my apartment with me? 3. Would you have sex with me? Of the females approached, 50% agreed to go on a date, 6% to go back to his apartment and 0% to have sex. Of the males approached, 50% agreed to a date, 69% were willing to back to her apartment and 75% agreed to have sex. This provides evidence that men have evolved psychological mechanisms to ensure success in short term mating. These include a desire for sexual variety, the tendency to let a little time lapse before seeking sexual intercourse and willingness to consent to sex with strangers.
Females invest heavily in offspring. As a consequence, for long term mating preferences, females tend to have high levels choosiness. This means being attracted to males who are able to invest resources in the female and her children, physically protect her and her children, show promise as a good parent and ensure minimal costs. Women desire and have a preference for males that have good financial prospects such as, a house and money.
Buss supports these universal sex differences by exploring what males and females looked for in a marriage partner. The study involved 10,000 people from 37 different cultures. He found that, women desired men with good financial prospects – a desire for someone with good resources. Whereas men placed importance on physical attractiveness. This provides insight to a women’s health and hence her fertility and reproductive value. Both are therefore engaging in behaviour that increases reproductive success supporting the sexual selection theory.
However, in the case of homosexuality, Buss’s argument cannot be accounted. This is because, homosexual relationships do not contribute to the survival of the species. But, homosexual couples do have the ability to adopt children. Therefore, a cost in parental investment is implicated. Furthermore, same sex relationships seem to have existed in most cultures throughout recorded history, so explanation for sexual selection cannot explain these relationships, therefore it cannot be generalised to all relationships.
Buss’s survey of mate choice suffers validity problems. An indication of expressed preferences is given rather than being a reflection of real life. Furthermore, people may express a preference for an ideal partner (intelligent, kind) but may have to settle for less. However, many real life studies support the mate choice hypothesis. A study of actual marriages in 29 cultures was conducted by Buss. This confirmed that men do choose younger women. Furthermore, men who divorce and remarry, tend to marry younger women.
Although Buss' study supports the idea that men prefer younger women, this may not be because of fertility. Some critics have tried to explain this in terms of social power: younger women are easier to control and are therefore preferable as mates. Kenrick et al. rejected this hypothesis by finding that teenage males are most attracted to women 5 years older than them: these women are not easily controlled.
In addition to this, there is gender bias in the research of short term mating. Although short term mating can be costly to females, they could also profit from this. Short term mating could be used as a means of ending a relationship with a poor quality male, or as a way of producing more genetically diverse offspring.
It could also be argued that evolutionary explanations are deterministic. It assumes that men will be motivated to have a high number of sexual partners and are less inclined to a long term committed relationship, and that women are motivated by resources. This ignore the role of free will and choice that both sexes have when deciding what relationship they want. There are males that settle down with one person at an early age and females who do not settle down and have children. Moreover, the theory can also be considered as being determinist because it suggests human sexual preferences are genetically programmed. The theory does not take into account our ability of conscious thought which gives us free will to make choices for ourselves. In fact human reproductive behaviour has changed dramatically over the last century, with non-heterosexual relationships, widespread use of contraception, and couples choosing not to have children. This implies that we have more control (free will) over our behaviour than is implied by the evolutionary approach.
Sex differences in reproductive behaviour could also be explained by an alternative perspective. It could be argued using the social approach that the idea that men are motivated to sleep around is something that is created and reinforced by society and socialization. Behavioural approaches would also explain this via the role of the media. The media could have a role via social learning theory as there are many social models in the media where males are exposed to this behaviour. Sexually promiscuous behaviour is also celebrated by the male peer group and this could be an alternative reason for this sex difference.