@Ebay, I wouldn't be surprised at all if creation stories such as the Garden of Eden deal with some misty communal memory of simpler times... perhaps times before a great drought requiring us to migrate. Africa, already subject to huge seasonal variation of rainfall in many parts has also been repeatedly turned into a desert and back again. In the last ice age, most recently, the region that is now the Sahara was well settled and lush with life... and the sea level was much lower (thanks to the glacial ice taking up a bunch of the water)... low enough to expose much of the flooded channels in the Persian Gulf to which you refer. If the Sahara is an appropriate measure, then I'm sure that the Fertile Crescent was even more so at that time. Subject to sudden changes (perhaps as little over as little as several generations) in their world - harsh changes that would have been hard to adjust to (and require moving from their former paradise) would certainly be good fodder for story. And once the story is told, like all good story tellers, they shape the story subtly over time - to be more memorable, more iconic, more supportive of their world view and view of the order of things (including religion). Of course, in their view, the climate changes and flooding would be God's doing! Dramatic natural events (comets, floods, lightning, earthquakes, etc.) have often been attributed to gods - and more so in pre-scientific societies, of course. Being self-centered beings (like all beings most likely are), we think it all must be punishment for something we did. Etc. etc. The story almost writes itself.