Chris, I saw your reply above re the number of fasts Shelton supposedly supervised. Maybe he did 30,000. Fine. I still doubt it, but no-one can prove it either way and it's not relevant now. I want to address the other point in your post:
You wrote "Fasting when well is superfluous, and that is why Shelton used the fast in diseased states, just as animals in the wild will fast when sick or injured or have to go without food involuntarily through scarcity. Rarely if ever do animals fast when well, unless at times of hibernation through the winter months."
Fasting when well is superfluous? Fasting --or starvation-- is commonplace in the wild. All creatures, large and small, from tiniest bacteria to the largest land and see animals undergo frequent periods of starvation, or fasting. And no, I'm not talking about the species for whom fasting is a normal part of their lives, such as hibernating bears, or migrating whales or birds, or seal pups stranded for months on the shore, etc. I mean the well-known fact that food is scares and its supply is highly unpredictable, or what you refer to as scarcity.
Absolutely each and every creature alive today evolved with periods of fasting -- which could be frequent or rare, long or short, coming with seasons or striking at random. Starvation is the grim reality of life in the wild; it was the main cause of death in all mass extinctions throughout Earth history. This means that the species alive today survived all those extinctions. We ALL have evolved with fasting as integral part of being alive on this planet.
You're right to point out that no healthy animal will fast while food is available -- but this is only because in the wild frequent fasts are a fact of life and the law is 'eat while you can!'
In this regard, humans are no exception (we certainly have not evolved on a farm with a reliable food supply). It is true though that we have come to the point in our history when food is always available and so we must arrange for our _very_natural_ fasts ourselves, voluntarily.
Why fast? The short answer: because that's how we evolved; this is what our physiology requires for optimal functioning.
I have not forgotten about your other points and will get to them later. Gotta run now :)