Adam and Eve were the island's protectors by Ricardus Alpert

For the longest time, the most popular theory regarding Adam and Eve was that they're time-traveling Losties who died in the same caves they once used to live in. Personally, I never liked that theory, and I think we can consider it debunked after Hurley addressed it in "Lighouse." Adam and Eve being two of the Losties doesn't explain the most intriguing thing about them- The stones they were carrying. So, who were Adam and Eve? Well, first we must ask ourselves a different questions. Have we ever seen those Stones later on? Well, we've seen very similar stones on the scale inside Jacob's Cave. That gives us a very strong hint to the identities of the bodies in the Caves.

I don't believe that MIB and Jacob were alone when they first came to the island. They might have even been brought there as Candidates for being the island's protectors themselves. I believe Adam and Eve were the previous island's protectors, who died in it's service.

I think that's the best way to tie up that mystery. It would give more depth into the Candidates' storyline, not to mention Jacob and MIB's storyline if they had a realtionship with them. Not to mention it would fit with Darlton's quote that Adam and Eve were proof they had a lot of things planned in advance.