what trade made the west african kingdoms of mali and songhai rich and powerful?; how did the bantu migration influence the development of great zimbabwe?; when human service providers first meet a native american client, they should; in general, the spread of islam to sub-saharan africa brought an increase in:; what kinds of goods were traded through the swahili city-states?; what does the architecture of great zimbabwe suggest about the kingdom?; adulis had a strategic geographic location as a; what is swahili and why did it develop?