ooh, I can answer this one. It seems abundantly clear that the premise of the article is that many people don't believe that African civilizations in that time

ooh, I can answer this one. It seems abundantly clear that the premise of the article is that many people don't believe that African civilizations in that time period could have built walls or drainage channels like this. It was little clues in the text that gave it away, like this: "That is because, says Mr Chirikure, Great Zimbabwe should be a “symbol”, not just of Africa’s power and potential, but of how outsiders have too often told Africans’ stories—and got them wrong." If the prevailing idea is that this relatively rudimentary technology was too advanced for the people of the region, then this discovery is evidence to disprove that. It doesn't have to be "sophisticated" on an absolute scale. Only relative to expectation. Imagine a 5 yr old wrote working Java code. Any working program, even the equivalent of a drainage ditch, would be worthy of praise. And something as simple as a linked list could be described as a "sophisticated technique" (for a 5 yr old) Understanding context and reading the article are, as ever, the keys.