I read recently (New Yorker, maybe) that states appeared not at the advent of agriculture, as has been posited for a long time, but at the advent of cultivation of cereals. All the places where nation states (or city states) formed had as primary crops corn, rice, oats, barley, and/or wheat, and all the agricultural societies that grew tubers, e.g., just kept on getting wiped out by the hill people. The way in which cereals grow are key to why this happened. First, they grow above ground (so they can't be easily hidden), second they only get harvested once per season (or at least at regular, defined intervals--so they can be counted), and third, they are storable for long periods (so they can be commodified). This allowed for the innovation of taxation, which was never before possible. Want to raise that army to kill the hill people? Well, cough up the wheat to feed them. So in a sense, the "format war" was between cereals and tubers (even though it was probably less choice and more geography that dictated the choice of crop).