There’s any number of scenarios that could and would drastically upend life as we know it and take what we regard as reality out behind the woodshed.

That indeed is one. And like many of the scenarios. It’s not completely hypothetical. There’s certainly enough folklore and half-remembered stories from across the world to suggest that our ancestors found evidence of such civilizations or in a few places. Met scattered pockets of survivors.

Time of course has seen the stories become embellished. So it’s not clear how much is real and how much is embellishment added by later generations.

There’s any number of scenarios that could and would drastically upend life as we know it and take what we regard as reality out behind the woodshed.

That indeed is one. And like many of the scenarios. It’s not completely hypothetical. There’s certainly enough folklore and half-remembered stories from across the world.