Across the Atlantic, centers of civilization had long flourished in Mesoamerica and in the Andes. The fifteenth century witnessed new, larger, and more politically unified expressions of those civilizations, embodied in the Aztec and Inca empires. Both were the work of previously marginal peoples who had forcibly taken over and absorbed older cultures, giving them new energy, and both were decimated in the sixteenth century at the hands of Spanish conquistadores and their diseases. To conclude this global tour of world civilizations, we will send our weary traveler to the Western Hemisphere for a brief look at these American civilizations (see Map 12.5).