There are echoes of multiple catastrophes like "The Deluge" and Thera in legend. No telling what we will find when the archeology of the last 25,000 years is recovered from the flooded ice age shores in 300-400 ft of water. Thales awed warring Greeks to scamper away from battle in 585 BC with his showmanship about blotting out the sun, showing us he could predict total eclipse. Bits of math and astronomy might be precious surviving threads no telling how far back. Plato's claim of priests' families handing down secret history / legends across the millenia might not be total bs. Time immemorial indeed.