The Sao civilisation may have begun as early as the sixth century BC, and by the end of the first millennium BC, their presence was well established south of Lake Chad and near the Chari River [REF].
Although some scholars estimate that the Sao civilization south of Lake Chad lasted until the fourteenth or fifteenth century, the majority opinion is that it ceased to exist as a separate culture sometime in the 16th century subsequently to the expansion of the Bornu Empire [REF].