The nature of sexual selection
intrasexual selection- one sex competes with eachother for access to members of other sex. Victors mate and pass on genes, losers dont. Traits that lead to success in these same sex contests will be passed on to next generation.Intersexual selection- Preferences of one sex for members of opposite sex who possess certain qualities.e.g.if females prefer tall males,over time there would be an increase in tall male as that would be the successful gene passed on.
Short-term mating-different mating stratergies evolved, some specifically for short term mating success. Men have evovled greater desire for casual sex and would seek it earlier in the relationship.Female behaviour would not be subjected to same evolutionary pressures.e.g over one year, a male who managed to impregnate large numbers of women would have passed more copies of his genes than a less successful male.however a female who had sex with the same number of men in the same time period would only produce a single child.Buss-the less time the man permits to elapse before sexual intercourse the more women he can impregnate in a given time.Buss and Schmitt- men appear to lower standards in context of short-term mating and show decrease in attraction after sex- an evolved adaption that causes hasty departure to ensure he doesnt spend too much time with one woman
.Long-term- both sexes typically invest heavily in offspring(sexual selection should favour high levels of choosiness). Poor long-term mate choice could be disastrous for both sexes because they would have wasted valuable resources. women have obligatory biological investment in their children so very particular about their mate. Buss- attracted to males who: are able to invest resources in her and child, able to pyhsically protect them, show promise as good parent and are sufficiently compatible to ensure minimum cost to he and child.Buss-sex differences in long-term mate choice- what males and females looked for in marriage partner. 10,000 people from 37 different cultures. results showed: women desired men with good financial prospects(resources, qualities like ambition). Men placed more importance on physical attractiveness(indicators of health,fertitility and reproductive value). Men universally wanted mates younger than them(also indicating increased fertiltiy). Both sexes wanted mates who were intelligent, kind and dependable.
Logic of sexual selection- The rationale behind sexual selection is that random mating is essentially stupid mating. It pays to be choosy, as genetic quality of a mate will determine half the genetic quality of any offspring. Low quality mates (unattractive & unhealthy) will be more likely to produce unattractive and unhealthy offspring. By mating with attractive high quality mate, offsrping are higher quality and individuals genes more likely to be passed on.
Male preference for younger women- One striking conclusion from Buss' study of 37 cultures is that men have a distinct preference fot younger women, a finding which supports the sexual selection theory, because the younger the women, the greater the fertility. However, some critics have argued that this preference is more likely to be in terms of social power- younger women are easier to control and therefore preferred as mates. Kenrick et al rejected this hypothesis. they found that teenage males are most attracted to women 5years older than them, despite the fact such women show no interest in them and are certainly not easily controlled by teenage males.
AO2: commentary continued...
Mate choice and menstrual cycle- research by Penton-Voak et al suggests that far from being constant, female mate choice varies accross menstrual cycle-Women choose slightly feminised version of male face as most attractive for long term relationship. However, for short term sexual relatiosnhip, during the high conception risk phase of menstrual cycle, the preferred face shape was more masculine. Sexual selection may favour women who pursue mixed mating stratergy. woman might choose main partnerwhose feminised appearance suggests kindness and cooperation in parental care, but might also copulate with more masculine male when conception is most likely. such males are likely to have higher levels of testosterone, which supresses immune system. a mal who is healthy despite this must have highly efficient immune system.
Importance of fertility- Although female humans ostreuos is hidden and so they give no signs of when they are most sexually receptive, research suggests that males find women more attractive at the most fertile point of menstrual cycle. Miller et al- Calculated tips earned by lap dancers in US at varying stages of menstrual cycle. Girls in most fertile stage earned double that of those who were not.
AO3: synoptic links
Mate choice in real life- Studies such as Buss' survey of mate choice might suffer from a serious problem of validity e.g. they give us an indication of expressed mate choice rather than being a reflection of what actually happens in real life. However, many real life studies support these mate choice hypothesis. For example, another study by Buss of actual marriages in 29 cultures confirmed that men do choose younger women. in fact, men who divorce and remarry tend to marry women who are increasingly younger than them.
Gender bias in short term mating- Although research consistently reports that men more than women have a desire for sexual variety and a greater willingness for casual sex, men could never have evolved this desire without willing females. Every time a man has sex with a willing new partner, the woman is also having sex with a new partner. Despite the fact that short-term mating can have serious consequences for women, there are also some benefits. Grieling and Buss- suggest that she could profit in a number of ways including using short term mating as a way of leaving a poor quality relationship(mate switching) or as a way of producing more genetically diverse offsrping.