Which factor most influenced the development of diverse cultures in pre-Columbian South America?

The most influential factor in the development of diverse cultures in pre-Columbian South America was the region's varied geography, which includes mountains, rainforests, and deserts. This diversity created distinct environments that shaped agricultural practices, settlement patterns, and social organization. For instance, the Andean highlands fostered complex societies like the Inca, while the Amazon rainforest supported smaller, nomadic tribes. Additionally, trade routes and interactions among different groups further contributed to the cultural richness of the continent.