Arrange these positions on language origins from the most gradualist to the most saltationist.

1. Language grew continuously out of primate call systems
2. Language began in gesture and shifted channel over time
3. Language assembled from several separately evolved capacities
4. A single change enabling recursion produced language essentially at once

Ranking them makes the axis explicit: the disagreement is about how many steps, and therefore about how much of language is a modification of things other animals have. The saltationist end is what makes the Pirahã recursion dispute so heated, a single counter-example matters far more to a one-step account.