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Influential Scientists and Their Hypotheses

It was not until the mid 1960’s that scientists truly began to analyze parental investment (Williams 1966), and it wasn’t until Robert Trivers wrote his widely acclaimed scientific paper Parental Investment and Sexual Selection (1972) that the discipline became worthy of consideration and analysis.  George C. Williams (1966) analyzed parental care from a cost-benefit standpoint, asserting that parents will alter the amount of care they provide their offspring, maximizing their offspring’s ability to survive while minimizing the cost to their future reproductive success. Robert Trivers (1972) took William’s ideas and expanded upon them greatly.  He defined parental investment as the total amount of investment from a parent into each of its offspring which serves to increase the survival of the offspring while simultaneously decreasing the parent’s ability to have more offspring.  In many species, the greatest that males will invest in offspring is their sperm (Trivers 1972, Diamond 1992, Gross 2005), while females invest an egg, pregnancy, and additional child rearing (Trivers 1972). In other species, males will invest in offspring by providing the female with resources and protecting during pregnancy, or helping to provide for, protect and raise the offspring after birth (Trivers 1972, Gross 2005).

Trivers used this idea of relative parental investment and outlined the effect it has on sexual selection among different species.  He theorized that in a given species, the sex that invests the most in its offspring will also be the most selective when it comes to choosing potential mates.  Conversely, the sex who invests least in the offspring will be less choosy about who they mate with (Trivers 1972).  In the case of animals where parental investment is divided roughly equally between both parents-such as humans-both sexes will be roughly equally as selective when it comes to choosing mates (Trivers 1985).  Trivers also theorized that the relative parental investment of each sex would dictate restrictions in mating.  For the sex that invests most heavily in rearing the offspring, the main limitation to mating is the availability of resources. On the other hand, the main limitation to mating for the sex that invests least heavily in offspring is the availability of the sex which invests most heavily (Trivers 1972).

Robert Trivers:

from: http://www.crafoordprize.se/press/pressphotos/2007.4.61632b5e117dec92f478000104288.html

~ by fknizner on April 14, 2009.


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