These are the remnants of their pyramids. And they developed, we believe, in the fourth millennium BCE. So this is around the same time as when Egypt first got unified by Menes, or you have the first Sumerians in Mesopotamia. And as far back as them, you have these khipu knots, which many archaeologists view as a form of writing, as a form of record-keeping. And it was even used later on by the Incas. So the big takeaway here is to challenge that misconception that the Americas somehow were not as populations and civilizations like everything else. It was only when the Europeans came in that all of that started to happen.