Since ancient times the Sudan region has been an arena for interaction between the cultural traditions of Africa and those of the Mediterranean world. Islam and the Arabic language achieved ascendancy in many northern parts of the region, while older African languages and cultures predominated in the south. The majority of Sudan’s population is Muslim, belonging overwhelmingly to the Sunni branch. A small percentage of Sudan’s population follows traditional animist religions, particularly in the Nuba Mountains. Although these animists share some common elements of religious belief, each ethnic group has its own indigenous religion. Virtually all Sudan’s traditional African religions share the conception of a high spirit or divinity, usually a creator god. Two conceptions of the universe exist: the earthly and the heavenly, or the visible and the invisible. There are many languages spoken in Sudan. Arabic is the primary language of much of the population and is the most common medium for the conduct of government, commerce, and urban life throughout the country. Both Arabic and English are official working languages of the country and were designated as such by the 2005 interim constitution. Most languages spoken in Sudan belong to three families of African languages: Afro-Asiatic, Nilo-Saharan, and Niger-Congo.