De-ignorance me... what is that story about? I've read other books by him (Uplift books, Earth) but not that one.
The world premise is machines automagically get better at performing their tasks the more they're used.
An axe will start as a piece of crude flint on the end of a pole and after much use will become a pure crystal axe head that is sized and bevelled perfectly to cut wood and the pole will smoothen, and get perfectly sized for the hands that wield it.
Dragging a travois over the same dirt area, the user will eventually have a metal track with a thin film of frictionless liquid between his start and destination points and the travois will strengthen, the tip will become metal, and it will fit the track perfectly.