This isn't really true. You're right that metaphorical interpretations are very old, but so are literal ones. The catholic church, who pioneered some great non-literalist interpretations, also used to excommunicate you if you didn't believe all of humanity shared a single male ancestor named Adam.

Pick a random medieval christian peasant, and ask him whether the Ark was a real boat, and let's place wagers on what his answer will be.

The genesis stories were literal before they were metaphorical, and opinions about the relative percentages of fact to metaphor have shifted wildly based on century, region, and denomination.