An idea–about the historicity of the gospels–occurred to me . . . although it’s speculation, and I have no evidence.
I have wondered if the Mesopotamian origins of the flood myth might be tied in with the paleoindians crossing Beringea into North America, and the great flood that destroyed the world might be a vague, cultural memory of Beringea being flooded at the end of the last major Ice Age.
An entire, fertile land was destroyed by being flooded, Beringea was a refugia for both people and a large variety of animals, and there is some archeological evidence that the people in the area used boats.
Problems with this idea are that I imagine Beringia flooded gradually rather than quickly, and the people in that time and place only had domesticated dogs, and no other domestic animals (except for maybe the horse, but this is unlikely).
We do know that certain legends which predate the end of the last Ice Age occur in Europe, Asia, and North America . . . if we consider The Cosmic Hunt story.
I also wonder if the story of Adam and Eve in the Garden of Eden is the remnants of a story about a power struggle between hunter-gatherers and new farmers at the very begining of agriculture.