Reproductive Behavior in Terms of Parental Investment

In 1972 Robert Triver's proposed that the differences in male and female mate selection and human reproductive behavior are caused by the amount of parental investment in offspring. He suggested that females invest more in their children than a man would hence why they are more choosey about their partner; he used biological stages of conception as an example of why women invest more. Males have a generally small about of investment as it only takes a few minutes before they may produce offspring whereas a woman would have to carry and nurture the baby for roughly 9 months. Males are also able to reproduce many times as their investment and time taken to produce gametes is significantly smaller than females, and are very capable of having many sexual partners and the only thing to limit the amount of offspring he produces is the amount of available female partners. As women have a limited supply of gametes that are much larger than sperm from the males and have a limited reproductive life of around 30 years, this limits the amount of offspring she can produce and carry in her life time. therefore the woman's investment in the child will be much larger as she has to continue to care for the baby after birth and stands to lose more if the child is weak or ill so must ensure the wellbeing and survival of her offspring to create the best possible reproductive success by choosing a suitable mate.

Later studies done by Buss and Schmidt in 1993 provide support for the parental investment theory by building on it, and proposing that we as homosapians are strategic in our sexual strategies. In the short term (2-3 months) men tend to look for fertility in a woman and the chances of her being reproductively successful whereas females assess mate insurance which can involve how likely he is to stay and support her through a pregnancy. In the long term (3 months onwards) men look for good parenting skills and faithfulness in the relationship, in this case women according to Buss and Schmidt are looking for similar traits in males such as commitment and protection but also resources such as economic assets. However it was pointed out by Weiderman and Allgier that human female mate choice may be the product of rational thinking and choices made in light of themselves lacking the resources (mainly economic) that a male may possess.

This evolutionary theory is demonstrated well by the research conducted by Clarke and Hatfield's and their study that investigated how likely male and female students would respond to being propositioned .The experiment they conducted suggested that males are much less picky in their selection of sexual partners and are more likely to have short term relationships than women as around 75% agreed to sex with a stranger. This much like Triver's theory suggests that men have a low investment in their offspring compared to women's. Other studies by Buss and Schmidt found that men were much more likely to engage in casual sex than women. They found