ABSTRACT
Most of the hunter-gatherers of the Old Stone Age probably lived in small bands of some fifty persons or less, organized around the family clan. Population density remained low as long as humankind derived its subsistence exclusively from hunting, fishing, and the gathering of wild plants. The shift from hunting-gathering to agriculture brought about a rapid increase in the world population and led to the multiplication of villages. Since human nature has been shaped by the conditions prevailing in tribes and villages, the genetic code which governs the responses of the human brain probably became adapted to social relationships involving only limited numbers of people. In the civilized world, people still try to protect themselves against the stranger by diffidence, hostility, and ostracism. The ceaseless mobility of the modern world constantly brings into the urban agglomerations new groups of people who constitute the modern equivalent of the Stone Age stranger on a magnified scale.
