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Evidence and Support for Parental Investment Hypotheses

The hypotheses regarding parental investment seem to be well established and supported by scientific evidence.  The original hypotheses asserted by George Williams (1966) and Robert Trivers (1972) regarding the cost-benefit structure of parental investment seem to be supported by several scientific investigations. In Kevin Woodward and Miriam H. Richards (2005) relatively recent study on parental investment and mate choice in humans, they find Trivers’ original hypotheses to be supported by their data, but with one small incongruity.   In their experiment, they had men and women rate how choosy they would be towards selecting members of the opposite sex for five situations: a single date, a one night stand, casual dating, steady dating, and marriage. The general trend they found was that as the risk of parental investment increased, so did the average choosiness of both the males and females in their study.  The incongruity they found was that male and female average choosiness score for a one night stand was less than their average choosiness score for a single date.  The risk of parental investment for a one night stand (which involves sexual intercourse) is much greater than the risk of parental investment for a single date, so according to Trivers (1972) the choosiness score for a one night stand should be greater than the choosiness score for a single date.  However, they hypothesize that the perceived risk of parental investment for a one night stand is less than the perceived risk of parental investment for a single date.  Their critique on Trivers’ hypothesis was that choosiness for men and women will increase as the risk of perceived parental investment increases (Woodward & Richards 2005).

Another investigation, Mart Gross and Craig Sargent’s (1985) study on parental investment in fish, found there to be a relationship between the amount of parental investment that fish provide and the benefit that the fish gain in their inclusive fitness as a result of providing the investment.  Specifically, they found that the male-only parental investment in fish can be explained by the fact that the male fish serve to increase their inclusive fitness, with a very low cost (Gross & Sargent 1985).  This directly relates to George William’s (1966) assertion that animals will alter their parental investment to insure the survival of their offspring at a minimum cost to their future reproductive success.  While most scientific investigations serve to back up these two men’s hypotheses, additional experiments would always be beneficial.  It is also important to note that while data may support Robert Trivers’ (1972) assertion that parental investment plays key role in sexual selection, there are other factors that play perhaps a larger role as well, such as attractiveness, health, and masculinity (Diamond 1992).

~ by fknizner on April 14, 2009.

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