EVOLUTIONARY EXPLANATIONS FOR PARTNER PREFERENCES

• Evolutionary approaches explain human behaviour in terms of adaptiveness and reproductive success.
• In 1992, male students showed greater distress (measured by galvanic skin response) when asked to imagine partner’s sexual infidelity, while women were more distressed by thoughts of emotional infidelity.
• These approaches argue that if a behavioural feature (for example, aggression) has been genetically inherited by one generation from another, then it must have a specific value for the human species; it might either help humans adapt better to the environment and survive (natural selection) or might help to attract a mate and have healthy offspring (sexual selection).
• Anisogamy is a concept in evolutionary explanations of partner preferences, explaining differences in partner preferences between males and females.
• Males’ sex cells (sperm) are produced in large quantities, quickly replenished and created continuously from puberty to old age.
• Females’ sex cells (eggs or ova) take a lot of energy to produce, are created in limited numbers during specific time intervals and their production only lasts for a certain number of fertile years.
• These differences mean that males and females need to use different strategies to achieve reproductive success.
• Before the invention of DNA testing, males could never be sure that a particular child is theirs, so the reproductively successful strategy for a male would involve having sex with, and impregnating, as many women as possible.
• For women, however, the energetically expensive process of producing an egg and then carrying a child in the womb for nine months would mean that she needs a partner who will be committed to the relationship in the long run and provide resources for her and the child, ensuring the child’s survival.
• These differences in mating strategies were demonstrated by David Buss (1989), who surveyed over 10,000 adults in 33 countries.
• Buss found that females universally put more importance on resource-related characteristics in a partner, such as ambition, high intelligence and good financial prospects.
• Males, however, preferred younger mates and put more value on signs of a female’s ability to reproduce, such as attractiveness and modesty.
• The principles of sexual selection described above mean that males and females use different strategies to select a suitable mate.
• Since human females do not advertise their fertility openly, males have evolved to pay attention to other signs in a human female’s appearance that show her ability to produce healthy offspring.
• Intra-sexual selection, on the other hand, is a preferred male strategy that refers to the evolutionarily developed features that allow a male to compete with other males for a female mate.
• Anisogamy can also explain the existence of two types of sexual selection: inter-sexual selection and intra-sexual selection.
• Intra-sexual selection can explain the differences in the body size and physical appearance between males and females, known as physical dimorphism.
• Waynforth and Dunbar (1995) researched ‘lonely hearts’ columns in American newspapers, and discovered that women tended to describe themselves in terms of physical attractiveness and youth (‘exciting, flirty, curvy’)
• Men, on the other hand, advertised their resources and intelligence more than women did.
• Inter-sexual selection, also referred to as ‘female choice', is based on the idea that due to the greater investment of time, energy and resources required from a female to raise a child, females need to be more careful when choosing a partner.
• Sexual selection favours physically strong and aggressive males, as males need to compete with other males for an access to a fertile mate.
• Female choosiness was illustrated by the study conducted by Clark and Hatfield (1989) where 75% of male students agreed to go to bed with a female student, while not a single female student agreed.
• According to Buss (1995), males have much less certainty than females that the child they are raising is theirs, which can explain the difference in jealousy between males and females.
• Women, on the other hand, have adapted to look for the signs of male’s ability to provide resources and protect themselves and a child.
• This idea was supported by Buss et al.
• A female having larger hips and a slim waist achieves this ratio, and men unconsciously interpret this as a sign that the woman is fertile but not currently pregnant.
• The winner of this competition reproduces and passes on to his offspring the genes that contributed to his success.
• Females don’t need to physically compete for a mate, meaning that physical strength and aggression will hold no evolutionary advantage for them.
• Males tend to be more jealous of their partner’s sexual infidelity, because this could result in raising someone else's child; females, on the other hand, are more jealous of their partner’s emotional infidelity, as this may result in withdrawing of resources from the female and the child and puts the child’s survival at risk.
• Buss (1989) has discovered that males universally put importance on attractive and healthy looks and youth, which are signs of fertility.
• Further evidence comes from research carried out by Devindra Singh (1993, 2002) who studied preferred waist-to-hip ratio as a sign of female fertility.
• Studying the measurements of waist-to-hip ratio of the winners of the Miss America contest for a decade, Singh found that men generally found any waist and hip sizes attractive, as long as a ratio between them is about 0.7.