Final answer:
The Ancestral Puebloans (Anasazi) required irrigation to farm, and due to the Great Drought, they left their villages to move closer to water sources or migrated south.
Step-by-step explanation:
Both the Mississippians and the Ancestral Puebloans were early American Indian groups that relied on agriculture. The Mississippians emerged in the Mississippi River Valley around 500 CE, developing large agricultural communities and creating a culture with a dense population and specialized artisans due to their surplus in corn-based agriculture. On the other hand, the Ancestral Puebloans, or Anasazi, who lived from 700–1300 CE in the Four Corners area of the United States, faced a dramatic climatic change known as the Great Drought. They became more insular, engaging in less trade, and practiced more intensive agriculture augmented by new irrigation techniques. This suggests that the Ancestral Puebloans could NOT farm without irrigation and, due to drought, left their villages and moved closer to water sources or migrated further south, joining groups that became the modern Pueblo cultures.