The Moche developed in the north coastal valleys of Peru between 200 and 850 ad. These societies evolved from earlier regional civilizations like Cupisnique and Gallinazo thanks, in part, to their advances in irrigation agriculture and the extension of fields into the deserts, which permitted population increases never seen before in the Andean region of South America. The Moche were never organized as a single, centralized polity but rather constituted multiple interacting medium- and small-scale regional societies, possibly complex chiefdoms and early forms of archaeological states, with two large regional divisions in the northern and southern valleys. Due to their fragmentary nature, there were more aspects that were differences between these societies than those aspects that were common. They seem to have spoken two different languages, Muchik in the north and Quignam in the south. Religions and ritual practices; a shared pantheon of divinities; and mythical narratives expressed in their iconography and performed in monumental structures, locally called huacas, were shared among Moche polities. It is hypothesized that Moche elites were also moving between polities, due to marriage and political alliance. The Moche excelled in multiple crafts, particularly metallurgy and ceramics, and were responsible for the development of multiple technological innovations. During most of their history, the Moche were isolated from other Andean societies, interacting only between themselves. This isolation was permitted by a specialization in the agriculture of the coastal valleys and in the exploitation of marine resources. Between 800 and 850, and due to external and internal causes, the Moche polities experienced different processes of rapid decline that led to the formation of a new generation of civilizations, the Lambayeque in the northern region, and the Chimú in the southern.