How could shifts in the physical environment have caused major changes in early civilizations?

Shifts in the physical environment, such as climate change, natural disasters, or changes in river patterns, could drastically impact early civilizations by altering agricultural practices and food availability. For instance, a prolonged drought could lead to crop failures, forcing populations to migrate or adapt their farming techniques. Additionally, the rise or fall of water levels in rivers could affect trade routes and settlement locations, influencing economic and social structures. These environmental changes often necessitated innovation and resilience, ultimately shaping the trajectory of civilizations.