My opinion is very idiosyncratic.
It is based on some premises:
1) Two fields of knowledge can state contradictory theories and yet be, at least, functional in their own areas. Quantum Theory and the General Theory of Relativity are still to be unified; Therefore, it is possible that theology and science state different things and they are different angles of a larger picture.
2) There is reasonable evidence that the laws of physics may change:http://www.newscientist.com/article/dn19429-laws-of-physics-may-change-across-the-universe.htmlhttp://news.bbc.co.uk/2/hi/science/nature/1991223.stm
3) That makes sense to me because the laws are created as well. Some Roman philosophers would disagree for they state that the laws of nature are a reflex or even manifestation of the inner order of God. I disagree, for it seems to me this is metaphysical pantheism. If the laws of the universe are created, they are subject to change and even to end;
4) The memory of a "golden age" exists in most of the ancient societies. Details may vary, but we do see it was a world that worked according to different "laws of physics": no disease, no decay, no death. This "era" was followed by another where humans were mortal but lived much longer, a "silver age", and, finally, our own age. The strict division may change, but there is this general thread from imortality to a very short lifespan.
Considering these 4 premises I believe that there were literal Adam and Even, a Garden, a serpent and a world where death did not exist. This world was possible because the laws of physics were different. Something changed though, and how that relates to the actions of the only sentient beings, I don't know, but that's the general witness of human collective memory. The Bible does seem to advocate key events where the laws of creation changed, the greatest of them, the abolition of spiritual death, which is to be followed by another change where physical life will be restored.
If this is correct, the creationist/designist dilema may be solved thus: the 6 something millenia of theology and the billion years of science for the universe maybe the exact same amount of time, only that the first is time as per the first laws of the universe and the second the same time as per the laws as they are now. Note that space and time themselves would change under this scenario I'm painting. It's like time itselfe could be denser, more compact, or thiner and more "enlogated".