Ultra-strict vegan diets. No meat. No dairy. No eggs. Lots of cantaloupe.
Great quote from chetday.com: "In spite of all the rhetoric from vegan diet teachers, there has never been a civilization in the entire world that has been able to survive on the vegan diet. Every culture depends on some type of animal products to a degree, be it eggs, milk, cheese, or meat (even insects in third world countries). This includes the Hunza people who are often falsely represented as vegan even though they eat dairy and some meat."