Ummm. The end of the last Ice Age, anyone?
Even today 80% of the world's population lives within 200 ft of sea level.
When all that ice melted off the continents, world wide sea levels rose 300 ft.
That's gonna make an impression on folks world wide...
I worded that wrong N&V - I really meant it would be hard to explain away, or to disprove. Just the opposite of what I managed to type. And not for the first time...But I think you are right on the money.