Having a symbol (for zero) is half the solution. It takes another leap to treat zero as number that participates in the usual arithmetic operations. From what

Having a symbol (for zero) is half the solution. It takes another leap to treat zero as number that participates in the usual arithmetic operations. From what I understand, there were a variety of non-standardized symbols or place holders used by the Mesopotamians (space being one). Zero was not treated as a number, but as a special case in their evaluator.