And ALL humans can cross water. Your “snail floated across on driftwood” idea is complete nonsense.
http://www.naturalnews.com/036268_Fukushima_beaches_invasive_species.html
If the snails were domesticated animals I would say the hypothesis might be correct.
The nonsense part of all this is that some dude traveled all that distance, ignoring the antelope and fish and other foods on the way, but made sure he could snack on the snails in his backpack...
Please remove me from your list. Most of the posts I’ve seen have little scientific justification.