CR an artifact?

The most widely accepted theory is that this effect evolved to improve survival during times of famine. "But we think that lifespan extension from dietary restriction is more likely to be a laboratory artefact,"
  says Dr Adler.

Lifespan extension is unlikely to occur in the wild, because dietary restriction compromises the immune system's ability to fight off disease and reduces the muscle strength necessary to flee a predator.-link 

I would also add that since the calorie restriction is done with dense nutrient enriched optimal nutrition, this is unlikely to occur in the wild.  Without optimal nutrition calorie restriction is said to fail to extend life, small amounts of nonenriched foodsource as found in the wild is in my opinion unlikely to provide optimal nutrition required for extension. edit: especially at levels that cr can work in some animals like 60+%, at 60% deprivation not only would the nutrient density likely be insufficient, but in an environment lacking resources the small amount of calories would be insufficient for exploration, cr appears to work and extend life even in calorie amounts beyond what would be sustainable in the wild.