How did Mesopotamian civilization have the greatest impact on the development of human civilization?

I would argue that the Mesopotamian civilization's
greatest impact on the development of human civilization came from its development of
writing.  The first known system of writing was the Sumerian cuneiform system.  Writing
has had a profound impact on human civilization, which means that the invention of
writing had a tremendous impact on civilization.

Writing
has changed our lives completely.  It has allowed us to transmit and store knowledge in
ways that would never have been possible without writing.  This means that we can,
effectively, know much more than people ever could before.  Because we have writing, we
can store all sorts of knowledge that allow us to have, simply as one example, many
kinds of technology that make our lives easier and more
fun.

Because of this, I would argue that the Mesopotamian
invention of cuneiform is their greatest contribution to the development of human
civilization.