For most of the course of human events, mankind lived in tribes. Behavior was regulated by intimate and persistent relationships, many with blood relations. The prolonged development required by human children assumed prolonged immersion in a cultural torrent fed by close physical proximity to fathers, mothers, brothers, sisters, aunts, uncles, cousins, grandparents, and the occasional stray outsider. Through this immersion, acceptable behavior was impressed on a child’s mind through a mix of deliberate and accidental lessons cumulatively applied over decades. When personal survival depended entirely on face to face relationships with others, the incentive to conform to what the tribe found acceptable was strong.
As Peter Turchin discussed in War and Peace and War, every human group, including tribes, is made up of three kinds of people:
knave: puts individual interests before group interests
saint: puts group interests before individual interests
moralist: conditionally puts individual interests before group interests
If moralists can punish knaves for not pursuing group interests, they will willingly put group interests ahead of their individual interests. If moralists can’t punish knaves, they opt out of pursuing group interests and only pursue their individual interests.
Since any human group is roughly ¼ knave, ¼ saint, and ½ moralist, this potentially pits ¾ of the group against the knaves. Within a tribe, knaves face an additional problem: the size of a tribe is usually smaller than Dunbar’s number. Dunbar’s number is the “number of individuals with whom a stable inter-personal relationship can be maintained” within the limits of the human mind. If group size is less than Dunbar’s number (around 150 people), moralists can know who’s a knave and who isn’t, allowing them to monitor and punish known knaves.
Consistent face to face intimacy with saints or moralists makes knavery difficult.
I hope that whets your appetite to go here and read the whole thing. Be sure to check out my comment near the end of the comment section, and Joseph Fouche’s reply which links to more great reading.
As background to Mr. Fouche’s points, consider these: