Chapter 15 Buss: Evolutionary Theory of Personality 447a cousin and a cousin more than a stranger because the brother is more closely
related to us and a cousin is more closely related than a stranger. This is not a
mathematical calculation any more than a spider needs to understand geometry to
spin a web. Moreover, when evolutionary psychologists talk about “strategies,”
these are not to be thought of as conscious or willful acts. In fact, people have
no awareness of these influences and when discussed often even regret them.
“Ugh, I am not attracted to him because of his resources and fitness!” “Sexual
strategy” is just a short-hand term for a cumbersome idea that evolution has
shaped our preferences for mates based on the fact that we are attracted to those
who produce healthy and fit offspring and ideally continue to provide for them.
This increases the likelihood that they will survive to reproductive age and pass
on their healthy genes.
Mechanisms Are Optimally Designed
People sometimes draw the conclusion that evolution produces solutions that are
optimal. In fact, some adaptations are rather awkward. Evolutionary change occurs
over hundreds of generations and there is always a lag between adaptation and
environment. Human preference for fatty and salty foods is a good example. In
ancestral environments tens of thousands of years ago, fatty and sugary foods were
very difficult to obtain. Yet they provide important nutritional benefits. Over the
last 100 years, fat and sugar have become cheap and plentiful. Our waistlines have
bulged to the point where two-thirds of adult Americans are now either overweight
or obese (Flegal et al., 2010). If they were optimally designed they would be more
efficient and respond more quickly to changes in the environment.
Related Research
The evolutionary model of personality cannot be tested directly insofar as we can-
not conduct studies over hundreds of generations. And yet, just like in biology,
there is much support for the evolutionary basis of human personality, which can
be divided into at least three general topics: temperament, genetics, and animal
personality. All three lines of evidence support the view that personality has a
biological basis and that these biological systems have evolved.
Temperament and the Pre- and Post-Natal Environment
Most every parent of two or more children knows that babies are different from
one another from their very first day. These differences in behavior have a bio-
logical basis and are known as temperament (A. Buss, 2012). Temperament lays
the foundation for later personality traits. Insofar as temperament is expressed
before and immediately after birth means it develops mostly from biological sys-
tems, but is modified by input from the environment. Moreover, differences in
these biological systems between individuals—some are more active and others are
more sensitive to sensory stimulation—have been shaped by natural and sexual
selection pressures, that is, by evolution.