In Mesopotamia, plant domestication led to population growth; in Mesoamerica, it led to plant extinction. Mesopotamian agriculture depended on seasonal rains, while Mesoamerican agriculture depended on river valleys. The people of Mesopotamia domesticated corn, whereas those in Mesoamerica domesticated rice. Domestication of grains occurred about 5,000 years earlier in Mesopotamia than in Mesoamerica.