This was my response when David Brin made the religious argument: monastic or hermit diets are not famous for their variety or density, and one of the most common religious strictures is no meat - which immediately makes protein difficult to obtain. And yet, even with these impoverished diets, you still see frequent claims of very long lifespans (which are usually dismissed as implausible, but that's assuming the conclusion for the purposes of this CR discussion).

When I read about Buddhist monasteries in Japan, for example, the diets seem to be mainly rice and some vegetables. Few nuts, fruits, fish, or meat like you see throughout the CRON recipe book.

So I regard the religion argument as weak; much better to watch the preliminary results of the human study or any primate studies.

Plus ¨servants, slaves, prisoners, or people who simply regularly don't have enough to eat¨ were/are all enduring stressful lifestyles, deprived of basic needs and enjoyment that surely lead to a shortened lifespan regardless of what they eat or did not eat -rendering any nutritional benefit (doubtful, due to the lack of control over one's diet patterns and contents) irrelevant in their cases-. One cannot consider a complex system like the human body without taking into account all major factors involved in its dynamics.