All right, now let's head south to the Inca civilization, which was older than the Aztecs and in some ways even more impressive. Founded in the 13th century, the Inca Empire ruled between 4 and 6 million people by the time the Spanish showed up in 1532. Trade and a very effective administrative structure held the empire together, which was even more impressive when you consider all the roads and temples that were built atop mountains, with nothing to haul things up those mountains except for llamas and people. The Inca had no written language, but they were able to keep records with knotted strings called quipus, and they were really good at integrating conquered people into the empire, mandating that people learn the Incan language. And vitally, they ordered every male peasant under Inca control to do unpaid work for the Inca government for a specified period of time each year. This system, which the Inca called mita, allowed them to build all those roads and temples. The Spanish would later adopt this system and the hierarchical system with the emperor at the top, except they would make it all, you know, much suckier.