PROGRESSStress isn’t good for human health. In fact, stress kills. Stress
increases the likelihood of developing heart disease, poor sleep, diges-
tive problems, and immune system impairment. It can also trigger
depression, which leads to low energy, poor motivation, hopelessness,
thoughts of death, and simply giving up, all of which militate against
survival. Among our evolutionary ancestors, people who were sensitive
to stress had a harder time extracting resources from environments that
represented a large change from what they were used to. They were
less successful hunters and less productive gatherers. That made it hard
for them to compete for reproductive mates, and sometimes they didn’t
even live long enough to have children who would carry their genes
forward to the next generation.
Not everyone gets stressed by change, though. A new job, a new
city, even a whole new career can be exciting and energizing for people
with dopaminergic personalities. They thrive in unfamiliar environ-
ments. In prehistoric times, they were more likely to cope well despite
radical changes in their way of life. They competed more successfully
for mates, and as a result they passed along their dopaminergic genes.
Over time, alleles that helped people adjust to unfamiliar environments
with ease became more common in the population, while other alleles
became rarer.
Of course, carriers of the 7R allele weren’t well suited to every
environment. People with dopaminergic personalities may do well
when coping with novel situations, but they often have difficulty with
relationships. That’s important because skillful social functioning also
provides an evolutionary advantage. No matter how big, how strong, or
how smart a person is, he’s not going to be able to compete with people
who work together as a group. Individuals shouldn’t fight gangs. In this
situation, when the need for cooperation is paramount, a dopaminergic
personality is a liability.
So it all depends on the environment. Under familiar conditions, in
which social cooperation counts the most, highly dopaminergic genes
become less common because their survival and mate-seeking advan-
tages diminish relative to the benefits of more balanced dopamine lev-
els. On the other hand, when a tribe picks up and heads off into the