Do you have evidence that in early times it wasn't taken literally? When did people start doing so, and what did they believe about the world's origin before that?
I think a metaphorical approach (along with a literal approach) to the Old Testament predates Christ. Certainly Philo of Alexandria examined the OT using a Platonic approach, similar to Greek philosophers' approach to their own myths. The Jewish and Christian scholars had a similar problem to the Christians in more modern times: resolving Jewish/Christian beliefs with the 'common knowledge' beliefs of the pagan philosophers.
On the Christian side, here is Origen, writing about 1800 years ago:
http://www.newadvent.org/fathers/04124.htm
But, that our meaning may be ascertained by the facts themselves, let us examine the passages of Scripture. Now who is there, pray, possessed of understanding, that will regard the statement as appropriate, that the first day, and the second, and the third, in which also both evening and morning are mentioned, existed without sun, and moon, and stars— the first day even without a sky? And who is found so ignorant as to suppose that God, as if He had been a husbandman, planted trees in paradise, in Eden towards the east, and a tree of life in it, i.e., a visible and palpable tree of wood, so that anyone eating of it with bodily teeth should obtain life, and, eating again of another tree, should come to the knowledge of good and evil?...
The same style of Scriptural narrative occurs abundantly in the Gospels, as when the devil is said to have placed Jesus on a lofty mountain, that he might show Him from thence all the kingdoms of the world, and the glory of them. How could it literally come to pass, either that Jesus should be led up by the devil into a high mountain, or that the latter should show him all the kingdoms of the world (as if they were lying beneath his bodily eyes, and adjacent to one mountain), i.e., the kingdoms of the Persians, and Scythians, and Indians? Or how could he show in what manner the kings of these kingdoms are glorified by men? And many other instances similar to this will be found in the Gospels by anyone who will read them with attention, and will observe that in those narratives which appear to be literally recorded, there are inserted and interwoven things which cannot be admitted historically...
Origen's comment about "who is found so ignorant as to suppose that God... planted trees in paradise" suggests that such a view was widespread in his time. The fact is that the fundamentalist dogmatic belief in the literal truth of the Bible is a modern invention, dating from the late 19th C. It's worth noting that it wasn't that the fundamentalist view that was mainstream, and then the liberal church broke away from that; in fact, it was the fundamentalist churches that broke away from the mainstream, more liberal churches.
There was an interesting sermon preached in 1922 called “Shall The Fundamentalists Win?” by Harry Emerson Fosdick, in which he railed against the new fundamentalists trying to drive out the non-fundamentalists from the church. Fosdick said:
http://baptiststudiesonline.com/wp-content/uploads/2007/01/shall-the-fundamentalists-win.pdf
Here, for example, is one point of view; that the virgin birth is to be accepted as historical fact; it actually happened... But, side by side with them in the evangelical churches is a group of equally loyal and reverent people who would say that the virgin birth is not to be accepted as an historic fact. To believe in virgin birth as an explanation of great personality is one of the familiar ways in which the ancient world was accustomed to account for unusual superiority...
In the evangelical churches today there are differing views of this matter [Christ returning]. One view is that Christ is literally coming, externally on the clouds of heaven, to set up his kingdom here. I never heard that teaching in my youth at all.
