Jack said in "House of the Rising Sun" that the bodies must have been dead 40-50 years based on the deterioration of their clothing. However, upon discovering the remains of a Nigerian smuggler in "Deus Ex Machina", Locke told Boone that normal clothing would decompose within 2 years and that the high quality polyester on the smuggler's body would take 2-10 years to get to its current condition.
As revealed in "Across the Sea" the bodies are actually almost 2,000 years old.
Adam and Eve were carrying one black and one white stone. Jack took these stones and neglected to mention them when Locke asked what had been discovered. (see also: black and white)
The skeletons were separated in their first appearance in "House of the Rising Sun", but were shown placed side-by-side three years later in their second appearance in "Lighthouse". It is unknown if this was a production error or if someone moved them in the intervening three years.
In a March 2008 Underground Online article, the producers talked about how the skeletons might give insight into the nature of the show and evidence that certain elements were planned early on. (article contains potential spoilers)
In a March 2009 Sky1 interview, the producers confirmed that Adam and Eve are not the actual biblical figures, and are "not the dog either."
In January 2010, after Barack Obama and his administration moved their State of the Union Address away from February 2 to avoid a conflict with the premiere of Lost's final season, Damon and Carlton said that Obama could ask a question about any unresolved mystery and they would answer it. According to the White House's ABC correspondant Jake Tapper, Obama allegedly asked the identity of Adam and Eve, to which Carlton replied "Good question! Have POTUS call us!"