▁bas in . ▁They ▁may ▁have ▁been ▁of ▁Nil otic ▁origin . ▁Even ▁the ▁span ▁of ▁their ▁civil isation ▁is ▁in ▁dispute , ▁with ▁various ▁estimates ▁putting ▁their ▁rise ▁at ▁some ▁point ▁between ▁the ▁ 5 th ▁and ▁ 8 th ▁century ▁and ▁their ▁fall ▁between ▁the ▁ 8 th ▁and ▁ 1 5 th ▁century . ▁The ▁prev ail ing ▁opinion ▁among ▁sch ol ars , ▁however , ▁dates ▁them ▁to ▁no ▁later ▁than ▁the ▁ 1 0 th ▁century . ▁At ▁this ▁time , ▁eastern ▁inv aders ▁entered ▁the ▁Ch ad ▁Bas in ▁and ▁conquer ed ▁them . ▁The ▁Sa o ▁likely ▁disappeared ▁through ▁inter mar riage ▁with ▁this ▁and ▁other ▁groups . ▁Many ▁of ▁the ▁current ▁eth nic ▁groups ▁in ▁the ▁Far ▁North ▁claim ▁descent ▁from ▁the ▁Sa o . ▁ ▁The ▁Kan em ▁Empire , ▁origin ated ▁in ▁the ▁ 9 th ▁century ▁AD ▁to ▁the ▁n ortheast ▁of ▁Lake ▁Ch ad , ▁and ▁from ▁there ▁expanded ▁in ▁the ▁region . ▁Islam ▁reached ▁Kan em ▁early , ▁and ▁the ▁r ul ers ▁converted ▁in ▁the ▁ 1 1 th ▁century . ▁Kan em - B orn u ▁strength ened ▁as ▁an ▁Islam ic ▁strong hold , ▁and ▁the ▁population ▁converted ▁as ▁well . ▁Emb ass ies ▁were ▁trad ed ▁with ▁North ▁African ▁states , ▁and ▁trade ▁increased . ▁The ▁r ul ers ▁launched ▁a ▁series ▁of ▁con quest s , ▁cul min ating ▁in ▁Dun ama ▁D abb ale mi ' s ▁( r . ▁ 1 2 2