The reference to Inuit & Masai was primarily of societies that existed on animal protein & fat diets and did not have a history of chronic disease markers such as autoimmune, heart or cancer diseases, not that I thought their diet was the ideal diet.
Regarding life expectancy of these groups, I think a simple measure of life expectancy in years is meaningless without the additional data as to how and when this figure was achieved and what other factors were at play. I did a little bit of reading on the Inuit and as far as I can tel the first recorded measure of average life expectancy was around 46 years in the 1840's from memory, but that would have probably also been similar to the white settlers at that time as well. Recent studies in Canada indicate Inuit life expectancy is a full 10 years lower than the general population, but that has more to do with social conditions than traditional diet, which very few are even able to simulate nowdays. Without knowing what the actual causes of mortality are, like physical injury, viral or bacterial disease or chronic diseases the life ecpectancy measure means nothing.
I also looked at the life expectancy of mammals (& other animals) and the average life expectancy had a generally linnear relationship with the size of the animal and no clear differentiation on the diet type, so generally the largest animals tended to have the longest average life expectancy, but not a hard and fast rule.
I also did a bit of reading on the Hunza (India), Abkhasia (central Asia), Vilcabamba (Equador) & Okinawa (Japan), all being quoted as extremely long lived, there is still a lot of questions about actual longevity as there is real data lacking, but what is not in question is that those that live to old age remain in good health both physically & mentally, so there is something to be said for looking into both diet, lifestyle & climate of cultures living in their traditional settings, just taking on a single factor like diet may be completely irrelevant to the matter. Currently the highest average life expectancy is in Andorra, small landlocked country in the pyrenees between France & Spain, average elevation of 2,000 m, and an average of 300 days of sunshine per year, diet is generally mediterranian type. The mediterranian diet has been much touted for health benefits, but does not seem to be anywhere near as effective outside the region so my guess is there is a lot more to it.
Some of the major similarities in all these so called healthy places seem to be Sunshine either through low lattitude or high altitude, both of which increase available UVB, A high level of varied daily activities resulting in significant nutritional turnover in the body as well as maintaining muscular, cardiovascular & bone strength, an outdoor lifestyle & exposure to significant temperature variations and a peaceful demeanour, contentedness with life.
A lot of my recent reading has been on Cholesterol functions & related topics and although humans can survive on purely animal based or purely plant based diets I do not feel either is ideal for longterm health, the ideal lies somewhere inbetween I feel. Cholesterol has been much maligned over the years, but is an essential body nutrient and is so precious to the body that there are multiple systems involved in it's preservation and recycling, it is the precursor to numerous hormones including Vitamin D and there is some suggestion that high cholesterol levels may be an indicator of lack of sunlight exposure. The liver is key to controlling and recycling cholesterol and the bile system is part of the system in disposing of excess remnants and other toxins, if the digestive system is not stimulated by dietary fats then bile is not released and this detox pathway is effectively blocked and these products accumulate in the liver, this effect is exasperated by high insulin levels from a high GI &/or High GL diet, particularly with high levels of fructose resulting in fatty liver & diabetes type issues. So with my current understanding I feel it is important to eliminate all high GI and processed carbs, and also to have a decent fatty feed occassionally to stimulate the liver bile function.
I am still learning as I go, we are currently into the six week mark of a paleo diet plan and it feels pretty good, one of the unexpected results is the lack of craving for sugar (chocolate, Icecream, cakes etc.), I think this is due to gaining some Insulin stability and getting it off the rollercoaster. We are basically 40% meat, poultry, seafood, 20% fruit, 20% veg & 20 % nuts, seeds & misc, No cereal grains, no dairy (except a bit of Yoghurt), trying to throw as much variety in as possible.
But I agree with you fully in that the more you learn, the more you realise there is to learn.
I am just an interested individual trying to crack the autoimmune nut.
Partner has Graves Disease, 5 years, showing good test results, looking forward to potential remission in the near future.
3 friends have MS, 1 just recently diagnosed, severity 7/10.