The Sao civilisation flourished in Middle Africa from ca. the sixth century BC to as late as the sixteenth century AD. The Sao lived by the Chari River south of Lake Chad in territory that later became part of Cameroon and Chad. They are the earliest people to have left clear traces of their presence in the territory of modern Cameroon. Sometime around the 16th century, conversion to Islam changed the cultural identity of the former Sao. Today, several ethnic groups of northern Cameroon and southern Chad but particularly the Sara, Kotoko claim descent from the civilization of the Sao.