On the other extreme, as I briefly mention, the Andes are not a place where anyone with sense would spend time working on inventing wheels for transport. People who wonder why the Incas didn't invent the wheel have never seen photos of the landscape in Peru.

And just to note, which you know - one reason domesticated pack animals will never go extinct until humans do is that there's always going to be areas where it's just easier to use animals than to try to build roads. No amount of bridges and tunnels is going to make wheels useful in the farthest, most mountainous hinterland.