[WalterBright]

Wheels also are not very useful without roads.

[pbhjpbhj]

Rollers for moving heavy items, pulleys for ...er ... moving heavy items; or are they not classed as wheels? Wheels are good for farming too, laying furrows, say. And making clay pots. And grinding corn. And crushing fruit.

Ah, this might turn in to a "What has the wheel ever done for us" sketch after the style of Monty Python.

[WalterBright]

I suppose it hinges on what is the simplest and most useful thing a wheel could be used for in a primitive society? Building a wheel with an axle and framework is not a trivial undertaking, and someone would need an immediate use for it to justify the effort.

(Try making a decent sized wheel out of a plank - it'll shatter along the grain. Getting a snug 90 degree hole for the axle isn't trivial, either, and without that the wheel will wobble so badly it'll be largely useless.)

[roywiggins]

Wheelbarrows relatively simple, you don't need a long axle and, of course, only one wheel. And they are pretty good on poor roads.

http://www.lowtechmagazine.com/2011/12/the-chinese-wheelbarr...

[WalterBright]

Making a spoked wheel is not simple. (Remember, all you have to work with is wood and a stone axe.)

A solid one is easier to make, but will be very heavy and have severe durability problems.

You also have never seen a machine in your life. You have nothing at all to guide or inspire you.

Wheels might have been invented and then abandoned and forgotten multiple times, because they were too hard to make and not that useful.

[pbhjpbhj]

I imagine the model would come from moving things on rollers, out perhaps from turning food on a spit.

From a piece of wood hanging on notched or Y shaped branches on which to hang meat for smoking/cooking to a spit to a pulley doesn't seem to far?

A simple barrow is a couple of sticks with a pulley. Though the utility over a simple dragged carrier is not much.