Personality traits like agreeableness and evolved responses such as group affiliation have traditionally been considered to be stable across situations. But evidence is accumulating that there is a lot of flexibility in our behavior. From an evolutionary point of view, the ability to respond differently depending on the particular social environment enables better adaptation than a strict set of behavioral “rules.”
For large tribes, circling the wagons in the face of threat is a much more effective survival technique than it is for small tribes. Living in a large tribe—or with many siblings—encourages interdependence and group cohesiveness because the cost of independence is high.
“I think what Andrew’s work is doing is marrying evolutionary approaches to culture and personality psychology, and telling us some of the ultimate reasons why people’s personalities and cultures might be different from each other in the first place,” says Cohen.
Knowing these reasons may help researchers find new ways to ameliorate intergroup conflicts. It is possible that cultures and religions that encourage large families respond to threat by banding together and ostracizing out-groups. Although empirical proof is lacking, Kenrick suggests that when negotiating with an outsized clan, the first priority is to underline your similarities. If they feel like you are one of them, you have a better chance of getting on their soft side.