Mike,
The model of the Nepalese child raised in America echoes my question and point -- that it is the daily exposure to such a physical task as load-bearing that forces individuals, perhaps by trial and error, to discover for themselves the ground path. Growing up in a culture where no such responsibility is present means not having the stimulus needed to make oneself learn. Again, necessity being the mother of invention.
Similarly, innovative ways to use the body to "solve a problem" seem to pop up in settings where a specific problem is offered. F'rinstance, I've noticed commuters on the subways in Boston who have learned how to shift with the lurching subway cars, and so are able to maintain their balance in situations where you'd expect they'd be thrown to the floor or sides of the car. These people are able to stand in a crowded train without holding a germy sidebar (my guess is that's why they would rather risk the lurching car!). No one taught them how to "subway surf" -- they wired themselves. Hey, I used to do it myself when I worked in the city, and the first dozen times I ended up having to grab a bar... but eventually even I wired myself to "surf."
I live in an area where fishing is still a regional industry. Often, I see lobstermen pulling up pots, fishermen hauling lines and nets, and shoremen lugging huge, heavy hoses to wash down the docks. The experienced ones are not pulling from the shoulders or depending on muscle. Did someone teach them this, or did they figure it out intuitively through constant body use?
Someone had to be the first to discover "silk reeling" or winding. My hunch is that it came from some homely activity such as net hauling, or heavy skein-winding, and not from martial roots, but was later applied by some bright mind who saw the usefulness. Maybe they were able to break down the process into excercises that could be orally transmitted. But my guess is that for the other uses of these body mechanics, the discovery was an intuitive one, again, spurred by the -need- to use the body in an efficient way to accomplish a specific task.
It is an interesting question, and one I've been pondering lately.