Further to this, we need to bear in mind that the ice age didn't end overnight 12000 years ago - in fact, there would have been a long period of time during which sea level was changing. Combine this with early settlements tending to be near rivers and/or coastal regions, and its very easy to see that flooding would have been an issue for all early human civilisations. I recall reading an article that explained that even if, over time, sea levels rise only gradually, you can still get catastrophic flooding. This is like a dam-burst effect, where nothing noticeable happens until a threshold is reached and suddenly the whole dam is washed away, with consequent flooding. I remember seeing an explanation like this for flooding in the dead sea region. In this light, the various flood myths may in fact be stories about how the ending of the ice age affected early human settlements.