Train a model on the world. Release it. It produces text. The text enters the world. Train the next model on the world.

The measured result is a narrowing. The tails go first — the rare constructions, the regional forms, the sentence that only one person would build. What remains is the centre, and then the centre of the centre, and after enough passes the output is fluent, correct, and describes an average that no longer corresponds to any population.

Researchers call this collapse and treat it as a failure mode requiring mitigation, which it is.

It is also an exact description of a culture with mass media, running since roughly 1920, at a rate of about one generation per generation. The tails went first. The regional forms went. What remains is fluent.

The machines are not doing something new to us. They are doing something familiar at a clock speed where it becomes visible, the way a film of a flower opening makes a plant look like it is deciding.