The Stacking Heuristic - A Candidate Cognitive Primitive for the Evolution of Monumental Architecture

Abstract Why did humans independently invent monumental architecture across widely separated civilizations? Existing explanations emphasize agriculture, religion, political hierarchy, engineering, and economics. These accounts explain why monuments were built. They leave a deeper question relatively unexplored: why does monumental architecture almost universally emerge through *vertically compositional* construction? This paper proposes that humans possess an evolved **stacking heuristic**: a low-level cognitive bias favoring the stable vertical composition of discrete objects. Rather than treating stacking as merely a motor behavior, I argue it functions as a domain-general cognitive primitive, observable in infancy, object play, tool organization, shelter construction, and ultimately architecture. Monumental architecture did not emerge from this heuristic alone. Cultural evolution repeatedly amplified an ancient behavioral tendency already embedded in human cognition. Monumentality emerges when symbolic systems recruit an existing construction heuristic. The hypothesis is stated so that it can lose. Its diagnostic content is not that humans stack — the leading rival predicts that too — but that humans *recursively extend* stacked systems, and that vertical composition persists even where alternatives are equally available and no harder. Predictions are ranked below by how much they can discriminate, not by how easily they can be confirmed.