800 A.D. All were strikingly similar. Each built great cities, created laws, developed games with complex rules, and had religions with a small number of important gods served by a priestly class. Each extended control over large territories, developing bureaucracies and armies, along with money, weights and measures, and histories. While different in style, they were the same in substance, inventing, with little or no borrowing, the same forms, works, and social structures. Even their arts differed in style, each based on its own geometric shape, and not in form.
Symbols represent groups.
Of course they were symbolic, but these symbols were different from tribal ones. These icons, by changing their meaning in context, could be used to represent any idea. Class or group was also the foundation for mathematics. A number represents a collection and not an individual. Operations on the collection, the heart of empire mathematics, were independent of what was being counted.