From Evolution and Human Behavior: Fitness costs and benefits of personality disorder traits
Extreme personality traits in humans often have detrimental life consequences, so they have long been supposed to be diseases. However, many other species display personality variants that are maintained due to their fitness advantages; in this case, they are construed as strategies. To examine the fitness costs and benefits of pathological personality traits in humans, we measured features of the A (socially odd, distrustful), B (incentive-seeking, selfish) and C (fearful, inhibited) clusters with the Personality Diagnostic Questionnaire-4+ (PDQ-4+) in a sample of 738 outpatients. Fitness relevant parameters like mating success, reproductive output, self preservation, and access to status were assessed with the Life Outcome Questionnaire. No fitness advantages were found for high-A subjects. In contrast, high-B subjects tripled low-B subjects with regard to mating success and had 39% more offspring. Further, high-C subjects outperformed low-C subjects in attaining status and avoiding risks. These findings help explain the commonness of some extreme personality traits in humans, and suggest that they should be seen as evolutionary strategies rather than as diseases.
My emphasis above. There’s no fitness advantage was found for being “socially odd, distrustful”, which is to be expected. Nerds and outcasts don’t get the girl – or guy, if they happen to be a girl in the first place. In contrast, “incentive-seeking,selfish” personalities were a winner. Maybe this explains the persistence of psychopathic traits in the population, that is, if psychopathy is synonymous or overlaps with this type of personality.