Hmm, but did the "whole earth" get covered? Or just the whole earth as conceived by the writer? Maybe it was just that part of the world?
No, the whole earth. Every major culture has histories that begin with a flood that covered the earth and there were only 8 survivors. Obviously it was very important to keep this info and with language it changed the details over time but the consistent thing is A flood that covered the entire earth, Ark, and 8 survivors. There are plenty of documentaries and articles about this and since has proven there was a world wide flood. It's not promoted because it proves the Bible right. Something people have a hard time with.
When the flood happened the earth shifted on it's axis and the canopy collapsed in the form of rain and the rest forms most of the oceans we have today, In addition, there were points in the earth where from water would come to water the trees and plants and all at. Also gone after the flood. When the canopy went away and the oxygen levels went down, people begin to get dumber, smaller and weaker.