To elaborate on this point: without agriculture centralization wasn't advantageous (or possible) but with agriculture centralization is advantageous--so central

To elaborate on this point: without agriculture centralization wasn't advantageous (or possible) but with agriculture centralization is advantageous--so centralized societies outcompete and are "selected for" over non-centralized societies and we end up with a "genotype" of societies having the trait of centralization.