Probably more of a multiplier. Wheels on pack animals are going to multiply the work that can be done many times over just a human pushing the thing. Sure, it

Probably more of a multiplier. Wheels on pack animals are going to multiply the work that can be done many times over just a human pushing the thing. Sure, it helps the human do more, but combined with a pack animal its orders of magnitude more than the human. And building a cart to fit to the pack animal is probably not the easiest thing to come up with, but looks obvious after seeing it, hence why the flow of technology isn't instantaneous.