Humans have always had tribal instincts, supporting those in their group and viewing outsiders with hostility. In primitive societies, people cooperated with other members of their group, and viewed outsiders as potential predators, and potential prey. Encounters between people who did not know each other were likely to be violent.
People in primitive societies identified members of their group based on personal knowledge, which limited the size of their groups. Anthropologist Robin Dunbar concludes that people are only able to have stable personal relationships with about 150 people, so primitive societies were small, limited to those the members knew personally, and interactions with outsiders were often hostile.
Adam Smith said the remarkable growth in the productivity of modern societies is a result of the division of labor (specialization), but that the division of labor is limited by the extent of the market. Primitive societies, which operated based on everyone having personal knowledge of its members, were necessarily small, which limited the extent of the market and therefore their economic productivity.
Advanced economies are more productive than primitive societies because institutions have been developed that give people an incentive to interact peacefully with others they do not know personally. Money is one such institution. If it is generally accepted, people can cooperate with others by making exchanges even when the people do not recognize each other, because they both recognize the money.
Governments that punish those who harm others are another such institution, or more accurately, a combination of institutions, including courts, police, and political institutions. You don’t have to like government to recognize that they do create order and allow people to live peacefully among those they do not know personally.
These institutions that enable cooperation among strangers stand at the foundation of the global economic progress that has occurred over the past three centuries. global cooperation has increased the extent of the market and produced unprecedented economic prosperity–because we are more willing to cooperate with people we do not know personally.