Steel and stone

It is true that the Incas had no written language and didn't use the wheel, but I've sometimes read that they didn't have metal tools, and that isn't true. They didn't have iron or steel, and they seemed to have thought of metal as a religious material rather than a practical one, but they did have bronze tools, including knives. At Macchu Picchu they seem to have built with the stone that was already on the mountain, and you can see that only one of these walls uses the perfectly sized and fitted ashlar masonry you see in Cusco. Still, to have cut all of this stone using only stone or bronze tools is mind-boggling.

While I was in Peru I read a novel called Civilizations, by Laurent Binet. It's an alternate history, where Atahualpa conquers Spain instead of the other way around. It's written in the style of a contemporary historical account, and so there wasn't the world-building or character development I would have liked, but it was very clever and it was amusing to see Europe (now “the New World”) through Atahualpa's eyes. One of his generals dreams of being the first to “discover” Italy. Jesus, aka The Nailed God, is “a local fable.”

This version of events is possible because a daughter of Erik the Red flees Greenland after a murder and sails south to Central and South America, where the Norsemen show the natives how to find and use iron. When Columbus turns up a few centuries later, he and his men are killed and Atahualpa uses one of his abandoned ships as a model to build his own. The Incas could live without a written language or the wheel, but if they'd had steel, history might have been very different.