> Lack of lost civilizations, where they ought to have arisen, needs explanation.
Well, lost cultures as advanced as, say, the builders of the Egyptian pyramids, but significantly older, is still an extraordinary claim.
In fact, claims of any kind of civilization existing require some kind of proof - it makes no sense to say "the British isles can sustain a thriving civilization today, so we should assume that there was a civilization present there 100k years ago, unless we have some evidence to the contrary (or at least wonder why no civilization flourished there some at that time)".
The Egyptians had no magic powers. They had population, surplus food, and regular human ingenuity. Anywhere that happens, civilization arises, like desert wildflowers after a rain. If the wildflowers don't bloom, that requires explanation.
You do understand that we need evidence for everything, right?
But bending over backward to try to discount the evidence we have because it must be not just regular, workaday evidence, but extraordinary evidence, is not science. It is, instead, hardscrabble turf defense, and nothing to brag about.
Furthermore, it is just as likely to be under 60+ ft of water. We don't need to find the water for a worldwide flood -- it's all still there, since the ice melted, right there in the sea. Literally tens (or hundreds, going back a little farther) of thousands of square miles of what was very recently dry land is now underwater, more than enough room for some regional empires.
People who lived on those square miles had to pick up and move uphill, and leave their ancestral homes behind. (That, as anyway, is pure fact.) Australians have oral history of the conflicts that move caused, because other people already lived uphill.
It's not an extraordinary claim. Nothing makes it prima facie unlikely. It just takes looking for evidence in places no one has chosen to look, yet.
We do know that a sophisticated civilization (tree-)farmed the whole Amazon basin, right up until they were wiped out by smallpox 500 years ago. LIDAR reveals many, many miles of huge earthworks. No one suspected, only a few years ago. We still know hardly anything about them. So, no, lost civilizations are not an extraordinary claim.
Lack of lost civilizations, where they ought to have arisen, needs explanation.