Between approximately 450 BCE and 950 CE, millions of Amerindian people living in today's Amazonia transformed the originally poor soil through various processes. Over many human generations, soils were enriched with charcoal from their low-intensity fires for cooking and burning refuse, animal bones, broken pottery, compost, and manure. The result is Amazonian dark earth (ADE) or terra preta, exceptionally fertile because rich in nutrients and stable organic matter derived from charcoal, which gives it its black color.