History of Chad Africa's major language groupings south of the Sahara Desert (except Khoisan, which is not considered a valid genetic grouping anyway), i. e. the Afro-Asiatic, Nilo-Saharan and Niger–Congo phyla, originated in prehistoric times in a narrow band between Lake Chad and the Nile Valley. The origins of Chad's peoples, however, remain unclear. Several of the proven archaeological sites have been only partially studied, and other sites of great potential have yet to be mapped. At the end of the 1st millennium AD, the formation of states began across central Chad in the sahelian zone between the desert and the savanna. For
Chad–Cameroon Petroleum Development and Pipeline Project which provided $46.6 million to finance Cameroon and Chad's equity in COTCO and TOTCO. Included in plans for the project was a revenue management law developed by the World Bank. This separated the oil revenues given to Chad into four required areas: a Future Generations Fund, health, education and other development projects, a fund to compensate the Doba region of Chad from where the oil was extracted and government reserves. The revenue management law also created the Petroleum Revenue Oversight Committee, which oversees how the oil revenues are spent, and includes members of both the Chadian government and civil society.