Ah, the flood destroyed the garden. Of course! :)
That still leaves two thousand years of human history (Eden to flood) where humans could have tried to get to the fruit though. The prize is eternal life for crying out loud! Surely Adam and all his descendants would be camped out in front of the garden, desperately trying to find a way in. We would have tales, passed down into history, of the hero Zog who managed to get over the wall but was mauled by a vegetarian lion inches away from the tree.
I guess my point is the Eden story has all the characteristics of a fable. And if it is a fable (which it is) then the fall of man is allegorical (not true) and the ransom sacrifice is not required and all Christian religions are no more valid than a Harry Potter fan club.