A puppet documentary. That is, a documentary that can be wildly inaccurate. The action would unfold on stage as if you’re watching TV late at night in some hotel in some forgotten city on some depressing business, wondering what life’s really all about — you flip the channels and there you are, a documentary about cavemen that answers all your questions about the meaning of existence.
The narrator would be our hero. He/she has that soft English accent you need to have to be a documentary narrator, and would provide an oddly poetic/surreal commentary on action on stage. It would slowly become evident that the narrator is having some kind of mid-life crisis, and is drifting radically off-script, so that by the end of the show the narrator has entirely lost it/found it/lost it again.
So the format would be, essentially, disembodied words over action. Caveman puppets, mastodons, dinosaurs (see: wildly inaccurate); segments entitled ‘the invention of Art,’ ‘the invention of Fire,’ ‘the invention of Self-Loathing,’ and so on.