When something is neither positive or negative it is in equilibrium, so whether we knew how to represent 0 or not is irrelevant - it was always "there". 0 is just the symbol we use.
yes, but we never knew it was there before the arabs Invented it, ( i'm sure it was the arabs). after that point we made astonishing leaps as a race, scientific formulae was born, math became a pure language of science, The impact of having 0 is staggering.
The Zero's idea took a little while to develop within the Hindu Arabic numeral system;
it is recognition that, in a place-value system (as in an abacus too), a numeral for zero is required in order to position the digits precisely.
The number zero was probably discovered almost as soon as numbers were discovered. ' Zero ' is after all synonymous with ' none '.
What took thousands of years was to invent a special symbol for the number zero, and then to incorporate it into a system of numeration.
The discovery of Zero was made only trice in history: by Babylonian scholars, the Hindus and the Mayans. The ancient Babylonians did not use zero in their numerical representations but left a blank sometimes to indicate the absence of units of a certain order.
The abacus' empty place-value was used to denote the absence of a unit and the zero too.