 The Native Americans of the Amazon rain forest may have used their method of developing and working in Terra preta to make the land suitable for the large-scale agriculture needed to support large populations and complex social formations such as chiefdoms.Rossetti et al proposed that the archaeological settlements associated with isolated or compound mounds were "systematically developed on top of extensive elevated surfaces formed due to natural sedimentary processes".Thus, the large Marajoara mounds or "tesos" are not entirely manmade.