All right first of all calm down.. you are going to do great in life.
Because they killed them and took their land and crops... not sure if thats the right answer but it dang sure would make sense
I believe the answer is radical republicans.
Answer: On the coast, they developed irrigation systems so they could farm in the desert. As a result, farming could support large populations both on the coast and in the highlands, where they built cities a full two miles above sea level. In fact, the cities built by these early cultures were some of South America's first.