This has certainly evolved into a very informative discussion. All of you folks have made brilliant points and opened my eyes to a better understanding of when and where to use roads. I would like to add to the discussion one factor that has not been mentioned tough.

Folks would have followed the easiest routes to landmarks visible at greater distances. They would not have had maps, trails or anything to guide them by except for the occasional glance of that landmark for which to get their bearings again. Once a path was cut, folks could easily and often find shorter or easier ways to get from point to point and over time, those trails would evolve into highways of travel. So, natural landmarks can be a great way to make sense of roadways through rough terrain when towns are no where in the area.

Another form of navigation was using the sun for guidance when traveling among uncharted territory. This could have led folks along miles of impractical and meandering routes that also eventually become established as highways.