"[T]he invention of writing... occurred somewhere around 3000 B.C. This is attributed to the ians... Sarton mentions that about one hundred clay tablets are known... that refer to Sumerian mathematics and table of numbers. These include tables of squares and cubes, square roots and cube roots, reciprocals and multiplication tables. The Sumerians had originated a decimal system. They seem to have had a natural genius for algebra and were certainly able to solve linear, quadratic and cubic equations. Their most surprising achievement was their handling and understanding of negative numbers, a concept that did not penetrate Western minds until centuries later."