442 Part V Biological/Evolutionary Theories
which our ancestors lived. Heightened anxiety would provide a signal of danger
and threat; its absence would quickly lead to extinction of the species. Consider a
hunter on the savannah. He hears the growl of a large animal and becomes fearful.
He drops back behind the bushes before the animal becomes aware of his presence.
If he did not feel anxious, he might not hide, with dire consequences for his safety.
By the same token, the other extreme—hypersensitivity to threats—would be
debilitating and disruptive to everyday functioning. If the same man who became
fearful at hearing the growl of a large animal also became fearful with every rus-
tling of leaves or every sound of the wind, he would have a hard time functioning
in everyday life. Having some degree of fearfulness is adaptive, and people with
that quality were more likely to survive, reproduce, and pass on that disposition.
Naturally selected traits are favored if they increase one’s chances of survival and
reproductive success.
Fourth, one’s capacity and commitment to work is the core characteristic of
conscientiousness. Conscientious people are careful and detail-oriented as well as
focused and reliable. Less conscientious people are less reliable and dependable
and tend to lack focus. Conscientiousness signals to others whom we can trust with
tasks and responsibilities and whom we can depend on in times of need.
Finally, the evolved strategy of openness involves one’s propensity for inno-
vation and ability to solve problems. It is closely aligned with intellect and intel-
ligence but also a willingness to try new things and a willingness to have novel
experiences rather than sticking with one’s routine. These people are the explorers
of a group—they forge ahead where others are hesitant. In ancestral times this
quality might be expressed in willingness to explore new territories for food or
vegetation, but today it might be expressed in artists and scientists who are at the
cutting edges of ideas and knowledge.
Buss (1991) argues that of the five personality dimensions, surgency/dominance,
agreeableness, and conscientious are the most important traits because they most
directly provide answers to a host of adaptive problems. For example:
∙ Who is high or low in the social hierarchy?
∙ Who possesses the resources that I need?
∙ With whom should I mate?
∙ Who might harm me or betray my trust?
∙ Who will make a good member of my group?
∙ Whom can I trust and depend on when in need?
Personality differences function to solve adaptive problems by providing answers
to these questions for both the individual and for others. In this sense they are
indicators of fitness, much like the peacock’s plumage.Origins of Individual Differences
As we discussed earlier, evolutionary theory is inherently a nature and nurture
perspective when it comes to origins. Buss and his colleague Heidi Greiling pro-
pose four distinct sources of individual differences (D. Buss & Greiling, 1999). In
essence, these sources of difference come down to nature (biological-genetic) and
nurture (environmental-social).