What if, much like building roads, or trails from tribal area to tribal area. How cool would it be to build a rail system, you would not have to have steam engines you could have carts that are man powered to move goods from one area to another, you could even build a rail to the forest to move logs, or an area where there was a mine of ore. Once animals become tame, you could get a horse or cow to pull the cart along the rail.