I remember reading this story a year or so ago from an archive from the internet, but I don't know who wrote it or when it was published.
The premise of the story was that these chickens in a crate fell off the back of a truck onto the side of a highway. The chickens can't cross the highway without getting run over and dying, so they stop doing that. Eventually they breed and natural selection results in them getting smarter and smarter.
They ended up developing some complicated myths about what was on the other side, and I think that eventually they get smart enough to build complex machinery and cross to the other side.
A pretty weird story.