I believe, however, that humans are the only animals that we know who invents tools for working together - and they have done that as long as we have… - Gerald Weinberg

The principle is simple and powerful enough to be Marvin's Fourth Great Secret: If what they've been doing hasn't solved the problem, tell them to do something else.

We were doing incremental development as early as 1957, in Los Angeles, under the direction of Bernie Dimsdale [at IBM's ServiceBureau Corporation]. He was a colleague of John von Neumann, so perhaps he learned it there, or assumed it as totally natural. I do remember Herb Jacobs (primarily, though we all participated) developing a large simulation for Motorola, where the technique used was, as far as I can tell, indistinguishable from XP.

The Third Law of Consulting: Never forget they're paying you by the hour, not by the solution.