the more i speculate, and the more i read up about Jacob and Esau... the more i think that all the times we have seen the dead on the island ( including Kate's Horse), but excludeing Walt... that it has been Jacob or Esau. boone appearing to Locke... the horse... Yemi... Ben's mom... maybe even Sawyers Boar? and what about Dave?
I like that thought... but was Kate's horse dead? Maybe there was Jacob/Esau, and then Smokey is their "pet", and Smokey is the one that takes the form of animal things, like the horse, and the polar bear that chased Walt, or maybe the boar, or maybe the Hurley-bird? (and possibly a T-rex judging by the Season One jungle noises and what happened to the original pilot... LOL.) Not sure about Dave -- we don't know he's dead, do we? He could've been a Jacob/Esau thing, or he could've just been a Hurley imaginarium... I can't figure out Walt, either. Or ghost-Horace in that time-loop... And we don't know if Harper was dead or not, do we?
OK, so this is way off from Adam and Eve...