History begins at Sumer because the Sumerians were undoubtedly the first to have a functioning system of writing.
For purposes of accounting, contracts, shipping, etc., little clay models were made of the kinds of commodities involved. For convenience, these models were then placed in clay wrappers. Then, so that the contents of the wrappers could be known without breaking them, little drawings of the models began to put on the wrappers. Soon it became obvious that the little drawings by themselves made the models superfluous.
The stylization of the models had already produced a certain abstraction and stylization in the drawings, which thus became proto-cuneiform – a system already able to represent numbers as well as concepts. Since thousands of the clay models have been found, the evidence for the process is abundant. No such antecedents have been found in Egypt or India, where writing began soon after the Sumerian precedent.
It is hard not to conclude that Sumerian influence, with the evidence of Sumerian artifacts to prove it, sparked the development of writing in those places. Where writing developed independently elsewhere, i.e China and the New World, Middle Eastern influence via Central Asia cannot be discounted on the former, while Mayan glyphs, only recently deciphered at all, had not progressed far, even three thousand years later, beyond the most basic versions of cuneiform or hieroglyphics.
On the other hand, the Sumerians were also doomed by history. The first chill came from the Semitic speakers, the Akkadians, who lived immediately north of them.