The history of Central Africa has been divided into its prehistory, its ancient history, the major polities flourishing, the colonial period, and the post-colonial period, in which the current nations were formed. Central Africa is the central region of Africa, bordered by North Africa, West Africa, East Africa, Southern Africa, the Atlantic Ocean, and the Sahara Desert. Colonial boundaries are reflected in the modern boundaries between contemporary Central African states, cutting across ethnic and cultural lines, often dividing single ethnic groups between two or more states.