As the Bantus in Africa increased trade with Arabs traders from the Middle East, Arab language, culture and religion began to permeate throughout Central and Southern Africa. As a result, many Africans converted to Islam and picked up Arabic (or at least Swahili- a mixture of Bantu and Arabic). This power point and cloze notes explains how trade and commerce made such cultural diffusion possible.
Alia Klein."Cultural Diffusion in Africa". September 2007. PowerPoint presentation.