Re: Baseline skillset
Setting aside the issue of the Nepalese/African/Sherpa porters (who probably display some sort of jin/ki skill, I guess), normal muscle is capable of an awful lot all by itself. I would be leery of automatically assuming that fisherman and farmers are using jin/ki.
I worked for a number of years as a bicycle messenger and then loading trucks for UPS. In both jobs, I reached a level of conditioning where my muscles just stopped getting tired. I never considered myself exceptionally "strong", but I could push myself well beyond what any of my non-manual labor friends could.
Loading trucks, I certainly learned how to hold the weight in my core and load up my legs, but I still used a helleva lot of muscle. Maybe I gained a minimal amount of body connection, but I certainly didn't learn the type of body skills I'm learning now. And the guys that worked those jobs for 10, 15, 20 years didn't display the type of body skills my teacher has, either. Their broad shoulders, backs, and thighs suggested they used muscle, too. But they could do that work for 5-8 hours at a stretch, day in and day out.
You don't need big bulky muscle to be really strong. But anyway, that all is the long way of me saying that the body skills I'm learning now are different from what I did doing manual labor.