In order to understand pre-Columbian societies, one must take into account the geographical features of the regions in which they developed. The societies of northern Peru spread out along the stretch of the Pacific desert coastline lying between northern Lima and the Tumbes region, bordering Ecuador. Shallow rivers cross the arid dryland here and there, most of them not fit for navigation, their waters descending from the Western Andean mountain chain to flow into the ocean. In these narrow valleys created by the flowing of the rivers, the Mochica, or Moche, society flourished and organized in a number of autonomous political entities governed by religious elites. The origins of the Mochica society date back 1,900 years. Fishermen and other collectors of the abundant marine resources found in the area met with people who arrived from the mountains, following the river course; the highlanders contributed with their agricultural knowledge and complemented the skills of the people from the coast.