If you look closely at the small table in the foreground, you can see two small stones on it. Since they seem so out-of-place in an apartment being remodeled, this has fueled speculation that they're actually the two stones Jack found on the bodies of Adam and Eve in the caves, way back in "House of the Rising Sun."
Furthermore, the writers have explicitly stated that these two rotting bodies are central to the mystery of the island:
Question: "What is the meaning or significance of the two skeletons that Jack and Kate found in the cave of season 1?"
CUSE: The answer to that question goes to the nature of the timeline of the island. We don't want to say too much about it, but there are a couple Easter eggs embedded in "Not in Portland", one of which is an anagram that actually sheds some light on the skeletons and hints at a larger mythological mystery that will start to unfold later in the season.
LINDELOF: There were certain things we knew from the very beginning. Independent of ever knowing when the end was going to be, we knew what it was going to be, and we wanted to start setting it up as early as season 1, or else people would think that we were making it up as we were going along. So the skeletons are the living -- or, I guess, slowly decomposing -- proof of that. When all is said and done, people are going to point to the skeletons and say, "That is proof that from the very beginning, they always knew that they were going to do this."
The anagram is probably Mittelos Bioscience, where Mittelos = "Lost Time."
Now there are currently three major theories around who Adam and Eve actually are:
1) Jack and Kate - Almost too obvious, really.
2) Amelia Earhart and her navigator, Fred Noonan - Given the presumed location of the island is so close to where Earhart's plane disappeared and the island's penchant for sucking in random aircraft, there's been a lot of thought that these skeletons are actually Amelia and Fred. The added bonus of this theory is that no time travel would be required for it to be true.
However, the one thing that makes me think these are NOT Amelia and Fred is that we've already seen an Amelia on the island. And she's alive.
3) Penny and Desmond - I really think the stones add credence to this theory. Plus, given the fact that Desmond's already traveled back in time once in the show and that Penny and Desmond are probably the most significant couple on the show. I could see a scenario where Desmond has to use his power to go back in time to save them all, but as a result he can never return. And Penny decides to go with him rather than live in the present alone.
Regardless of who they are, Adam and Eve are a central part of the show's mythology and one of my top questions I want eventually answered.