i wanna think widemore used to be the captain of the black rock........ (he knows what the black rock is because he was bidding on documents at the auction)
he is the one who found it..... thats why he considers it his! there is obviously an aging issue on the island. He very well could have still started the D.I. over the years while maintaining a young age...... maybe he left the island with the intent to come back but while he was gone ben "moved" the island!