Last night I started reading Douglas Preston's 'The Lost City of the Monkey God' and was stricken by his descriptions of how dangerous and difficult to traverse the dense jungles of Central America are. This made me wonder if the jungles made it impossible to strike out far beyond one's own city or village, and therefore isolated empires from each other. I also have a really poor idea iof when each major empire (the Aztecs, Maya, Incas, Zapotec) existed and if they overlapped.

Is there evidence of these developed civilizations interacting? If so, what was generally the nature of their interactions?