Yes, to an extent, I believe that there were definitely times of scarcity, but I'm not sure if the scarcity was frequent, as on a week-to-week basis. I give those cavemen and women the benefit of the doubt when it comes to knowing what they needed, where to get it, and how to get it. They had to be a lot tougher and saavy than we can imagine just to get by. Nor do I think that it was a Garden of Eden.
Were there times of scarcity? Certainly. And in these times of scarcity, would it be not only beneficial, but essential, for the body to react with conservation? I'm not talking about how sudden bursts of energy and clarity may occur to a hungry hunter. Those kinds of moments were likely selected for, and this is what our adrenal systems and flight responses are all about. If one looks at societies where scarcity is felt on a week-to-week basis, one will discover that all of these peoples have one thing in commom: failure to thrive. I would suggest reading Colin Turnbull's The Mountain People for a horrifying example of this.
Regardless, I'm not saying that periodic fasting is a bad thing. I have done it and plan to do it additionally myself. My point is more one of evolutionary logic than to shoot the idea down. And I maintain that everyone should do what they believe is best for them. I also think that if you are already at or near your desired weight that fasting may be more beneficial than to someone who's got a ways to go.
Some good sources:
http://www.ultrametabolism.com/ (the book is very informative)
and
http://www.drweil.com/drw/u/id/QAA400132
(I'm not normally a big fan of Dr. Weil, but he does have a cautious approach to anything extreme.)
"But fasting and near-fasting routines such as the Master Cleanse are not effective weight loss tools - they alter your metabolism in a way that actually may make it harder for you to lose weight or easier to regain the weight once you go back to the way you normally eat. Most people compensate for the deprivation of the regimen by increasing their caloric consumption afterward.
"If you really want to lose weight, forget about drinking lemon juice and maple syrup and learn the basic facts about nutrition and optimal health, including the glycemic index, anti-inflammatory diet, and recognize any unhealthy relationships with food."
Again, I want to stress that I am not anti-fasting! I'm just not going to adopt it as a (weekly) way of life for myself.
"Unhealthy relationships with food"? Anybody?