Which of the following best explains why some Ancestral Pueblo groups moved south?
1. Long periods of drought made farming difficult in the southwest.
2. The Ancestral Pueblo groups formed alliance with tribes in the south.
1. Long periods of drought made farming difficult in the southwest.
This option is the most likely explanation as environmental factors, such as drought, have been known to greatly impact the ability of ancient civilizations to sustain themselves through agriculture. In times of scarce resources, communities may have been forced to migrate to regions with more favorable conditions for farming and survival. On the other hand, forming alliances with tribes in the south would not necessarily require a large-scale migration of entire groups.