Yes, Chris, we can probably better survive on an island than on the savanna, but OTOH animals isolated on an island get rel.smaller brains (this makes the Danakil hypothesis unlikely).
All fossil & other evidence suggests that our early-Pleistocene broad-bodied, heavy-boned, flat-skulled, large-brained ancestors (archaic Homo) dispersed along Eurasian & African coasts, parttime diving for seafood. Biologically this is obvious – except for paleo-anthropologists who were indoctrinated at universities that our ancestors left the African forests for the African plains.

http://www.discoveryuk.com/web/naked-and-marooned-with-ed-stafford/photos/naked-and-marooned-with-ed-stafford/

This is an interesting (TV) experiment on human survival capability. The choice of habitat for it is exactly what we’re talking about: A tropical island. That would indeed be a Homo sapiens’ best chance to survive on its own on this planet. No one would dare try a similar thing on the tropical savannah.

Wrinkly fingers don’t contradict the coastal dispersal model, on the contrary apparently: they might help swimming, and possibly feeling and/or grasping underwater for seafood. IMO it’s difficult to use wrinkly fingertips pro or against AAT.