To the landlubber scholars, ancient people only moved overland, and when the ice melted and water covered up various isthmuses (isthmi?), they stood on each side of the strait saying "oh shucks", y'know, in cave language.
I’m still trying to figure out where this stigma may have originated. Deep set fear of water based on ancient religious ideology? Such as Hammurabi casting the accused into the water to determine innocence or guilt, sink guilty/float innocent? Or the account of Jesus walking on water in the bible creating the assumption that no one knew how to swim before that time? I wonder where the assumption that early man could never have floated truly originate?