Sexual Selection

All sexually reproducing animals seek reproductive partners, or mates, who will 'enable them to enhance [their] reproductive success' (Singh, 1993, p. 293). We do not consciously (or even unconsciously) evaluate those we meet in terms of their ability to help us procreate. We may feel a strong sexual attraction that has been 'hard-wired' into our biological constitution; but this is not a strategic plot designed to maximise the representation of our genes in future generations (Buss, 1992). Individuals that are highly physically attractive possess an assortment of characteristics that gives them a high mate value. It has been argued that the psychological mechanisms underlying perceptions of sexual attractiveness should be sensitive to environmental cues that correlate with mate value (Buss, 1992), thus accurately guiding human mate selection without conscious rationalisation.

Trivers (1972, cited in Millar, 1998) explained why males court and females choose in terms of the higher level of necessary parental investment required by the female of nearly all species of animal.

Millar (1998) cites studies by Anderson (1982), Catchpole (1980), Mollard (1988), and Ryan (1985) that have all shown that females of many species exhibit strong preferences for particular male characteristics. With regards to humans, Singh (1993) published his first study into the adaptive significance of female waist to hip ratio (WHR), and in 1995 he published a study investigating male WHR. Both these studies found that males and females definately do have preferences for a specific range of WHRs. WHR outside these ranges are perceived to be unattractive, and Singh has explained this in terms of fat distribution, which gives a good estimation of the health of an individual. Men prefer women with a waist-to-hip ratio of between 0.67 and 0.80. Women prefer men with a waist-to-hip ratio of between 0.85 and 0.95. Singh (1993) states that evidence is accumulating that supports the belief that WHR is an accurate somatic indicator of reproductive endrocrinological status and long-term health prospects. WHR is primarily due to the distribution of adipose tissue. Adipose tissue distribution is directed by human steroid hormones; primarily oestrogen and testosterone. Therefore, WHR can be used as a crude measure to determine the health of the endocrine system. By judging if fat is deposited in correct proportions by viewing the WHR, we can estimate the potency of an individuals circulating sex hormones. There is an optimum density of fat deposited around the waist and hip area for each of the sexes, as both too little or too much fat can be viewed as reliable indicators for health problems, and therefore impact upon potential suitability as a mate.

Mating Strategies
If a man has sex with dozens of women in a one year period, then he is likely to father many children. However, no matter how many men a woman has sex with, she can only have one pregnancy (NB: during breastfeeding, the hormone oxytocin is released by the posterior pituitary gland, which prevents ovulation). Thus, the preferred sexual strategy of males across many species is polygyny, which helps to ensure the male has many offspring with a larger proportion of the 'gene pool'. Males therefore spend a lot of time and energy finding and attracting mates, valuing females that are fit enough to produce healthy offspring and to tend to them fairly autonomously from the father. According to Buss (1992), human females value a mate that is willing and able to: (1) provide for her and her progeny, (2) protect her and her offspring, and (3) engage in direct parenting activities such as caring for and teaching the children, while providing social support and opportunities; that is, someone who is prepared to invest a lot into the relationship. This supports the axiom that women prefer monogamous relationships, or serial monogamy.

Therefore, men prefer short-term mating strategies, whereas women prefer longer term relationships that will satisfy the preferences detailed above. A study by Clarke and Hatfield (1989, cited in Buss, 1999) asked people this what they would do in the following scenario: Imagine an attractive person of the opposite sex walking up to you and saying 'Hi, I've been noticing you around town lately, and I find you very attractive. Would you have sex with me?' One hundred percent of the women gave a definate 'NO' answer, but 45 percent of the men said they would have sex with that stranger. This makes sense when we look at the relative input required from both parents in pregnancy and raising a child. Effectively, a man may have nothing to do with the women ever again after sex. If the women got pregnant however, she would have to invest nine months with the infant developing inside her and then have to care for the child very intensively for at least three to four years. There is an awful lot more at stake for a women.

Darwin's Theory of Evolution

Environment of Evolutionary Adaptation


The social function of intelligence

References and Bibliography

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