Like those in the Eastern Hemisphere, almost all indigenous civilizations or cultural traditions in the Americas were based in river valleys or closely related to river systems. Then, why have not they given birth to an indigenous civilization that is as strong as those in the Old World? In this chapter, a comparison of two regions with contrasting ecologies—namely, the varzeas (meaning “floodplains”) as an Amazon region where there is extensive land and unlimited food resources, and the coastal valleys of Peru as a region with circumscribed agricultural land—reveals that it was the scarcity (not the abundance) of natural resources that eventually led to the establishment of agricultural societies and of more advanced civilizations. At last, I argue that the Americas’ favorable external conditions had negatively influenced their cultural evolution and development during the pre-Columbian era, and that, if the current geopolitical pattern does not change, the negative influence will continue to exist.