The regions north of the Rio Grande saw the origin of three, or perhaps four, agricultural complexes. Two of these developed in what is now the southwestern United States. The Upper Sonoran complex included corn, squash, bottle gourd, and the common bean and was found where rainfall was greater than about 200 mm (8 inches) annually. The Lower Sonoran complex, with less annual precipitation, included corn, squash, cotton, and beans—tepary bean, lima bean, scarlet runner bean, and jack bean (Canavalia ensiformis). Corn appears to have been the first cultigen in the Southwest. Direct radiocarbon dates place it at the Bat ...(100 of 27369 words)