The Portuguese explorer Diogo Cão reached the mouth of the Congo in 1484. Commercial relationships quickly grew between the inland Bantu kingdoms and European merchants who traded various commodities, manufactured goods, and people captured from the hinterlands. After centuries as a major hub for transatlantic trade, direct European colonization of the Congo river delta began in the late 19th century, subsequently eroding the power of the Bantu societies in the region.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): What is an example of something that was not traded between the Bantu and European merchants?
unanswerable