It is not that the water rose a fraction of your 400 foot drop, but that earth rises and falls with natural tectonic activities, like volcano and earthquakes.

Yes, given that the archeological record shows no previous use of advanced materials and the paleobotanical record shows no chemical residue in plants to suggest previous industrial capacity. There were no “more advanced” ancient civilizations.

Now, if you want to talk about the First Civilization–which was a global white civilization on the cusp of the bronze age that fell when the oceans flooded the world at the end of the last ice age 12,500 years ago and is remembered in the Bible as The Flood–that’s another matter. What we are (((told))) is the beginning of human civilization and agriculture is about 7-8,000 years later than when it actually started.