islam is "natural"(i don't really agree with the term) to africa, but so is christianity and judaism...just not european christianity...remember jesus was black...so was damn near every biblical prophet...romans destroyed many of the churches in africa...it's astonishing...i visited some of the ruins...i think the question of how indigenous a form of spirituality or a belief system is to a region can only be answered by that regions involvement in the advent of said beliefs....it could be argued that africa was the first place that islam was practiced freely...after the death of muhammad his successors travelled to "spread the word" but were shocked to find mosques already established....