The development of agriculture enabled Mesoamerican peoples to form large, settled societies that developed centralized governments and high levels of social and political stratification. The reason for this, in a broad sense, is that societies that produce surpluses can afford to maintain elites that draw their status from the ability to extract wealth from the rest of society. In Mesoamerica, the main crops were maize, beans, and squash, three symbiotic vegetable plants which were cultivated in fields alongside each other. In the subtropical climate of Central America, they yielded large quantities of food, enough to support the cities that made up the series of civilizations that rose in the area, including the Olmecs, Zapotecs, Aztecs, and Maya, to name a few. Agriculture was instrumental in the development of these dense, complex societies.