Early humans somehow knew this storyline, and attempted to write about it in the best manner with which their early evolved brains(created, if you prefer) could grasp.
I don't think there's much difference in brain evolution between the early Hebrews and us. It's what we have observed in nature (despite Faith's clams) that has enabled us to conclude that much of what the Hebrews wrote was wrong.
Perhaps the definition of what is human versus what is evolved animal is differentiated by the idea of a name.
I don't "assume" it, I conclude it to be so because any other explanation makes no sense.
When you see a pile of leaves, do you "conclude" that they all came from one tree because any other explanation makes no sense?
What you've shown is evidence that floods happen. We already knew that. I've seen four myself.
What you haven't shown is evidence of one giant tree or one giant flood. That is what makes no sense. And you know it makes no sense because you don't use the same logic to conclude that all leaves come from one giant tree.