Sexual Selection

'It is debated whether evolutionary explanations of sexual selection accurately explain human behaviour'

Suggesting evolutionary explanations do explain human reproductive behaviour, women are primarily responsible for inter-sexual selection (mate selection) as they must carefully select a partner who is most likely to protect and provide for their off spring until it reaches sexual maturity. This causes men to compete with other men (intra-sexual selection) to be selected by numerous, high status, fertile women. Trivers (1972) explains this due to differences in the level of investment in child rearing made by men and women (Parental Investment Theory- PIT), a woman has limited reproductive possibilities (one ovum per month), and invests more than a man (as she must care for the off spring during pregnancy and childhood). Therefore, she uses inter-sexual selection to pass on her selfish genes (Dawkins) by selecting the most attractive males- one who can provide (with financial status) and protect (muscular). Whereas a man has numerous reproductive possibilities (millions of sperm a day) and invests less in childcare. Therefore he can be less selective, ensuring that he passes on his selfish genes by competing to procreate with as many partners as possible. 

Strong evidence to support evolutionary factors comes from Clarke and Hatfield (1989) who used confederates to approach both male and female students to offer casual sex. 75% of men agreed to the request by 0% of women did. This shows that men are more promiscuous due to their numerous reproductive possibilities and women and more selective due to their limited reproductive possibilities. However, this study can be criticised for having low external validity- leading to low population validity; the extent to which the findings can be generalised to wider populations, as they only used students which does not represent all adults, therefore can only be generalised to students and no the general wider adult population.

Further evidence to support the role of evolutionary factors comes from Singh, who showed that men select a partner with a hip to waist ratio of 0.7, suggesting child-bearing hips (a sign of fertility); and Gross , who showed that women are attracted to a shoulder to waist ratio of 0.85-0.9, suggesting broad shoulders (a sign of protection).  As these were shown cross-culturally, it adds strong research support for the role of evolution. It is considered to be culturally absolute; the theory can be fairly applied to all cultures. This is because Singh carried out this experiment on all different cultures and received the same result from each. This means it can be generalised to all cultures as all cultures were tested. 

Convincing evidence for the role of evolutionary factors in aggression, comes from Buss and Schmitt, who found the on average men sought 8 sexual partners in the next two years, where women only sought one. This shows that men are more promiscuous; due to their numerous reproductive possibilities, and women are more selective, due to their limited reproductive possibilities.

However, undermining the role of evolutionary factors in sexual selection, this theory can be criticised for being simplistic because it ignores other important influences. This is because the theory stresses the importance of heterosexual procreationand therefore ignores homosexuality; couples who decide not to have children or to adopt; and blended families (step children). 

However, undermining the role of evolutionary factors in sexual selection, this theory can be criticised for being simplistic because it ignores other important influences. This is because the theory stresses the importance of heterosexual procreationand therefore ignores homosexuality; couples who decide not to have children or to adopt; and blended families (step children). 

For the same reasons,it can be criticized for being constrained and alpha biased, as it ignores the idea of free will and unfairly exaggerates the differences between men and women. This is because it suggests that we are genetically programmed to select the exaggerated characteristics proposed by the theory, which is obviously not always the case (as women are now known to cheat in a relationship).

Also, further undermining the role of evolutionary factors, sexual selection theory can be criticised for being historically biased as it was developed in one time and unfairly applied to others. This is because it was created in 1972 and therefore does not reflect the cultural changes that have occurred since that time (e.g. female breadwinners and male househusbands). 

Finally, it can also be criticized for being unfalsifiable as it cannot be tested using an independent or dependent variable, and speculative, as it makes assumptions that go beyond the findings of research. This is because it is impossible to test an evolutionary theory as the period of evolutionary adaptation occurred millions of years ago. 

Therefore, whilst it is likely that sexual selection may accurately explain human reproductive behaviour, evolutionary explanations can never wholly be accepted because they are unfalsifiable.