The oldest known civilization in South America, as well as in the Western Hemisphere as a whole, the Norte Chico civilization comprised several interconnected settlements on the Peruvian coast, including the urban centers at Aspero and Caral. The presence of Quipu (an Andean recording medium) at Caral indicates its potential influence on later Andean societies, as well as the antiquity of this unique recording system. The stone pyramids on the sites are thought to be contemporary to the great pyramids of Giza. Unusually among Andean cities, no evidence of fortifications, or of other signs of warfare, have yet been found in the Norte Chico.