A tribe has a common territory and a common dialect. There is feeling of unity among the members of a tribe especially to face outside aggression. The members of tribe consider themselves to be descendants of a common ancestor and therefore all members are connected by blood relationship. The members of a tribe are generally endogamous and they have a common culture and religion. They may also have independent chiefs or heads in which social authority rests.
The replacement of customary control with formal control is an outcome of the establishment of a nation state. State formation occurs as a result of a mixture of political, economic and historical circumstances. A state is formed when one group gains centralized political control over all the other groups within the society usually by means of coercion. The ruling group is then faced with the problems of maintaining the control and for this a formal legal system is essential.
The states develop as a result of the unequal distribution of economic goods those who control more resources can gain control over the rest of the society. But societies have been identified in which neither conquest nor economic control has led to the formation of a state.
The crucial factor in the formation of a state is the degree of centralization of authority. Multiple centers of power and authority compete and prevent a state from forming. As traditional ties are broken down and territorial boundaries become more precise a state emerges. Eventually one person or group assumes the central authority in the society with a monopoly on the legal use of force.