Guess they never heard of Noah.
They have, of course, but the problem is there isn't a scrap or shred of evidence, or any logical mechanism, for a simultaneous world-wide flood.
Most likely candidate I've seen for the cause of the almost-extinction was the eruption of the Supervolcano Toba in Indonesia 70,000 years ago...the last Supervolcano to have erupted.
Well in the Flood story there were eight people left after the flood to populate the world, but only two chimps. I wonder how that would explain the chimps having more genetic diversity when they started with a smaller gene pool in the first place. The Noah story helps not a bit here . . . sorry.