I've got a theory. Western Mediterranean is much shallower than Eastern Mediterranean.
So once upon a time it's possible that the Western Mediterranean was a low-lying basin of land that could be crossed from Africa to Spain. Thus, the pre-Sahara civilization (aka Atlantis) that had trade routes across that region, would have been able to easily expand up into Spain, which became "Atlas' Land". Atlas being the name of every king of Atlantis.
Once the Strait of Gibraltar broke, I'm guessing the Atlantic Ocean flooded the Mediterranean, obliterating the Western Mediterranean living space and eliminating those land bridges.
The yellow areas being the parts of the Mediterranean that were probably above sea level at one point and got flooded out when Gibraltar broke.
This might actually explain the Great Flood. As in, maybe it wasn't a worldwide event, but simply a massively catastrophic event centered around the Mediterranean area that wiped out all of this land.
This would also explain why the legend persisted for thousands of years that King Atlas "dropped the western edge of the world" and it caused a great calamity. Gibraltar would be the western edge of Atlantis' domain if it ran from Spain (Atlas' Land) down through Richat and east through the not-yet-Sahara.
Time went by and Atlas' Land became Atalan, then Catalan, then Catalonia/Cataluna/Catalunya depending on what dialect is using it.
Mediterranean Sea became what it is today. Legend persisted about the time Atlas dropped the western edge of the world, and the Greeks made it into a story about a guy who was "holding up" the world. Sahara Desert emerged and expanded, causing the disappearance of Lake Chad and the rivers that flowed through that region, along with the Eden-like forested regions.
End result, the Mediterranean lowlands (and probably a lot of northern Africa) were destroyed by a flood, the Sahara region civilization was overcome by the calamity of sand, and Atlas' Land (probably the last territory they expanded to) was really the only part of that civilization that was spared from massive bad luck and destruction. The Sahara-region survivors migrated to Egypt and the Middle-East and helped the evolution of Ancient Egypt and Babylon. The survivors of the Mediterranean disaster probably retreated into Spain and Italy and eventually became Romans after a couple hundred more generations.
After a few thousand years civilization recovered to the point that historians could start keeping real records again that would be preserved, but by then most of the information about Atlantis and Atlas being an organized civilization was 6,000 year old legend. Thus, "modern civilization" starts up largely from scratch around 6,000 years ago. The Library of Alexandria was the greatest repository of information on any of these eras of time and somebody burned it down.
