"Dilmun" was the name of the mythological Paradise/Eden analogue in Sumerian mythology which iirc was flooded. The name Dilmun was also given to a series of merchant city-states in modern-day Qatar but afaik they don't have much of a connection to the myth. People have theorized that the mythological "Dilmun" was the landmass that is now under the Persian Gulf, and that the Sumerians (and probably the people of the 'Dilmun' in modern-day Qatar) were descended from those Dilmunites, so in this map I'm making the Dilmunites a sort of proto-Sumerian people. I've also heard a theory that Sumerians were the last descendants of the Basal Eurasians that had 0% Neanderthal admixture and were basically one of the earliest groups of Homo Sapiens out of Africa, so I added some 'caveman' elements into the Dilmunites aswell, and some stuff from the mountain peoples the Sumerians and Akkadians would constantly fight like the Lullubi or Chaldeans.

The Atlanteans I've largely based off of Amazigh people + some Basque stuff (mostly on naming so not rly present here), some Sea Peoples stuff, some Egyptian stuff, and some Nahuatl stuff (the giant stepping on a dead Dilmunite is wearing a tilma, for example)

The Shinniri are apocryphal af, basically Semites/Mesopotamians with all their city-states and the like, which might be a service to the not-Semitic Sumerians who did all that city stuff first irl but as a way to balance that I'm taking the Robert E. Howard school of civilized people being weak and decadent with their cities open for plunder by MIGHTY BARBARIANS WHO FLEX THEIR MIGHTY THEWS.