A comprehensive evolutionary framework for understanding
the maintenance of heritable behavioral variation in
humans is yet to be developed. Some evolutionary psychologists
have argued that heritable variation will not be
found in important, fitness-relevant characteristics because
of the winnowing effect of natural selection. This article
propounds the opposite view. Heritable variation is ubiquitous
in all species, and there are a number of frameworks
for understanding its persistence. The author argues that
each of the Big Five dimensions of human personality can
be seen as the result of a trade-off between different fitness
costs and benefits. As there is no unconditionally optimal
value of these trade-offs, it is to be expected that genetic
diversity will be retained in the population.