Or, maybe God destroyed the tower at Babel and confused their languages, so there simply wasn’t anyone left who could speak Sumerian anymore. The Sumerians were a cosmopolitan people composed of various racial groups, centered around the correct geographical area, around the same time as described in that Biblical story.
Where did you get that?
Sumerian creation myts in the Enuma Elisha place their Eden as Dilmun (or modern day Bahrain)
About their racial background hmmm... there doesn't seem to be enough dna evidence one way or the other.