there are many more older cultures then sumeria that have the same stories. check out south america, south africa. scientist have track the female DNA to the first female (or EVE) to south africa 150,000 years ago.
there are tamples and gold mines around there dating back to 10,000 BC. they have discoverd writings there about the flood and creation as well. all the ancient culures that talk about creation reference simular gods to sumeria. in the sumerian tablets they talk about not one but brothers. look at the old testiment, from book to book, sometime god was nice and somtimes not. almost like the two feuding brothers from the sumerian tablets.