I think the large earth monuments were part of successful agricultural projects. The stone work was to keep the cultural organized and focused. The most successful left large stone constructions.
Dubai is far more architecturally impressive than London, New York, or Los Angeles. Now compare their city GDPs. That was kind of my point.
Some degree of excess wealth is clearly a necessary condition for large scale stone monument construction, but the inverse doesn't hold. A society could have a lot of excess wealth and lack any cult, state mandate, or other construct to drive stone monument building.
