By Timothy J. Killeen Prior to the arrival of Europeans, the Amazonian lowlands were home to several hundred ethnic groups living in tens of thousands of villages with a population estimated at between four and fifteen million inhabitants. Over millennia, these societies transformed landscapes along the main stem of the Amazon River and its major southern tributaries by developing agricultural practices that created dark earth soils, a technology that improved the physical and chemical properties of tropical soils, increased their productivity and ensured their sustainable use over centuries. …