I tend to agree with your theological views, but your science is a bit off. There were modern humans of species H. Sapiens long before Sumer. Modern humans first emerged about 300,000 years ago according to the best available scientific evidence, and this occurred in Africa, not Sumer. Sumer is generally accepted as the first example of civilization, which includes among other features the presence of a written language, a centralized government, and extensive agriculture. It’s not correct to state that the people of Sumer were the first humans, however.
We ought to distinguish the biological species Homo Sapiens from the theological concept of "human". Being human as far as Genesis and St. Augustine and Humani Generis are concerned means being descended from Adam and, therefore, sharing in Adam's original glory and Fall. That's the sense in which I am using "human".
What you are talking about from 300,000 years ago is anatomical "humanity", which is a different thing. I don't see how Homo Sapiens in the Rift Valley can be descended from Adam given the context in Genesis. The Tigris and Euphrates are by the Garden. Adam is doing agriculture before and after the Fall, and his sons live in a world where there is already intensive farming and herding. Cain builds a city. The context of Genesis 2 and following points to civilization and the Neolithic in Mesopotamia.
Now what exactly to make of contemporary populations around the world and previous versions of Homo Sapiens I do not know, and it is something I am studying intensely. But at least we are getting away from the "ensouled ape" idea that the sound mind tends to rebel against.