a bit off topic but isnt the best idea if to experiment on animals to try apes or monkeys because of the closest relation to humans?
I think gene expression tests on human cells are also a good idea. We already have an idea of the gene expression patterns of CR, and know of several genes involved in the aging process.
if you like to know what I think is that it is unlikely that it will extent human life significantly or by now we should already noticed it.
Depends even if it drastically slowed the aging process, it likely won't stop tooth decay and might not stop lens decay. Also we'd need to know what the adequate dose range is, and consistency in dosing. Taking it from time to time when you're in pain will do nothing. Under dosing or overdosing will likely either do nothing or be harmful.
Even at appropriate dosing, some aspects of aging like tooth decay are unlikely to be affected and could limit lifespan in ancient populations without adequate technology or medical support. Also even if it did affect the aging process substantially a side effect could also limit potential lifespan increases.
It is not inconceivable that it hasn't ever been taken consistently at an adequate dose indefinitely.