The evolutionary explanation for partner preferences
Evolutionary theory sees differences in male and female sexual behaviour as having arisen due to different selective pressures. Males are not certain of paternity, so their best strategy to pass on their genes is to impregnate as many females as possible, which has little reproductive cost, as males produce lots of sperm. Males therefore seek signs of fertility in women, such as youth, healthiness and child-bearing hips, and indulge in intra-sexual competition with other males to obtain high-quality females. Females are certain of maternity but produce few eggs, so reproductive activity has a greater cost for them. Therefore their best strategy is to indulge in intersexual competition and select fit males to produce healthy children. A female therefore seeks wealth and resources in males, indicators that they will be able to provide for her and her children. Females also get males to spend time, effort and resources in courtship, to reduce the chances of males deserting and leaving childcare to females. Males indulge in courtship rituals to compete and display genetic potential and have evolved to be bigger to compete with other males. Both males and females benefit from copulation with non-partners, males by increasing chances of reproductive success and females by widening the genetic diversity of their children, increasing survival chances.
Fig 9.1 Evolutionary theory predicts differences in types of jealousy between males and females
Schutzwohl & Koch (2004) tested the idea that males fear sexual infidelity while females fear emotional infidelity. 100 males and 100 females were presented with four imaginary scenarios involving social situations, each with two alternative responses. The important scenario was: ’Imagine you discover your partner formed a deep emotional and sexual relationship with another person. Which aspect of your partner’s involvement would make you more jealous: (1) the deep emotional relationship, (2) the passionate sexual relationship?’
Both sexes reported more jealousy over emotional involvement, but more males (37 per cent) than females (20 per cent) selected their partner’s sexual involvement as making them more jealous. Women who selected emotional infidelity reached their decision faster than women selecting sexual infidelity. Men selecting sexual infidelity reached their decision faster than men selecting emotional infidelity. Therefore, men and women who choose their adaptively primary infidelity type — sexual for men, emotional for women — rely on their initial response tendency suggested by their respective jealousy mechanism.
• Cartwright (2000) found females with symmetrical breasts were more fertile than those with non-symmetrical breasts, supporting the idea of body symmetry as indicating reproductive fitness. This was supported by Penton-Voak et al. (2001) finding females prefer males with greater facial symmetry.
• Pawlowski & Dunbar (1999) found women aged 35—50 years were more likely to not disclose their true age in personal advertisements, which suggests they do so in order to not be judged by males as being less fertile and therefore increase their reproductive opportunities.
• Toma et al. (2008) found that in personal advertisements men were more likely to lie about their education and income, while Kurzban & Weeden (2005) found women were more likely to lie about their weight being less than it really was, supporting the idea of resource richness being attractive in males and physical indicators of fertility being attractive in females.
Evolutionary predictions about sexual behaviour are generally supported by research into animals, with behavioural variations understandable by reference to differences in environmental pressures. This suggests that differences in sexual behaviour have evolved.
The practice of checking partners’ emails and mobile phones can be seen as a modern form of mate-guarding, where checks are made on partners to see whether they are being sexually and emotionally faithful, which would reduce our reproductive fitness.
Females finding males who take drugs, drink alcohol and engage in risky activities as attractive may occur due to such males advertising their reproductive fitness by being able to safely consume toxins and survive potentially dangerous situations.
The evolutionary explanation cannot account for romantic relationships where couples choose not to have children or homosexual relationships that cannot result in pregnancy.
Younger males desiring substantially older females goes against evolutionary predictions — though this could be explicable as males wanting to mate with females proven to be fertile.
The fact that many women today have resources of their own and therefore do not need resource-rich males goes against the evolutionary explanation.
Female choosiness and male competitiveness can be explained by gender role socialisation, as well as through evolution.
Learning that jealousy is a natural, evolutionary response to perceived sexual and emotional threats could help partners in relationships threatened by intense feelings of jealousy to come to terms with it and therefore save their relationship.