I don't know much about the history of The Dig, but I believe there were at least two earlier versions than the one we got to play. Brian Moriarty was the director, or some other important guy like that, of one of the early versions.
I'm sure SAM will be able to tell you more. Or he will tell you to wait until he opens his site. Then we can find out everything and more.
Also, this article
will probably satisfy your thirst for the time being.
I also remember reading a long article about the game's history, complete with lots of pictures of the early versions. I have been unable to find that one, though.