Let's see...lots of thoughts here. I think it would be difficult to find all the sources that have led me to my conclusions, but I'll try. Probably a lot of my thoughts are informed by my experiences in the outdoor survival community.
In general, I'm suspicious of any new-fangled dietary intervention (which of course includes our overdependence on simple carbohydrates and other processed foods) that hasn't been normal in a significant portion of the human population for a long time. I think most of our ancestors ate mostly plants. As we say in the survival community, "You can try to hunt, but plants are nice because they don''t run away." Fish are easier too. But big game? Even skilled hunters struggle to get enough for the whole village, and when they do, there are limited means of storing/preserving it. If they have domesticated animals, they have to invest so much in grazing/winter feeding that it would seem a poor choice to eat them very often. Also, most wild game has little fat (although more than plants, and I agree fat is very important, particularly for brain development).
Other than the Inuits and Masai, I can't think of any other indigenous people who are keto. Perhaps you know some more?
And there's some evidence that even the inuits and masai eventually suffer because of their long-term dietary limitations (https://nutritionstudies.org/masai-and-inuit-high-protein-diets-a-closer-look/), though I suppose it could be due to other aspects of their lives.
And our ability to say what's "essential" is limited by our ability to measure all the miniscule operations of the human body. Yes, somebody can live for years and years on a very limited diet (https://www.nydailynews.com/life-style/health/teen-eats-ramen-noodles-13-years-article-1.1312782) but long-term, I think you're better off with a variety of less-processed natural foods. As I was saying about the body doing triage - when deficient in a nutrient, the body will send that nutrient to the most vital functions of the body - it'll keep the heart beating, etc, but other processes (brain development and maintenance, joint lubrication, skin elasticity etc) might start to suffer, more so as one grows older. (https://www.youtube.com/watch?v=CEsonu2kFjY, https://www.foundmyfitness.com/episodes/bruce-ames) You must excuse me for being a shameless Dr. Rhonda Patrick fan girl.
So I think our bodies evolved to be healthy under the conditions that existed for most of human life: Lots of exercise and a minimally processed (grinding and cooking, mostly) plant-based diet (with intermittent meat consumption, or if on water, more often fish). So that's how I try to eat, with the important addition of VARIETY and modern medicine. My ancestors may have been limited to a couple of healthy food sources, but as a modern person, I can partake of healthy food sources from all over the world, lucky me! Also, I would be dead without modern medicine, because I had an ectopic pregnancy (which developed while I was doing keto!) lost a quarter of my blood and would have died without immediate intervention.
I do think that we benefit from spending time in ketosis, though, as our ancestors likely did in times of scarcity. I'm sure you know the benefits like autophagy etc.
I finally decided that my ideal diet would be to fast one day a week, stay in ketosis for the next day, and eat similarly to how they do on the Nicoya peninsula (fish for me, I don't eat red meat) within an 8-12 hour window for the following 5 days. I haven't followed through yet though - easy to say, tougher to do!
That said, I really do think overconsumption of super-processed carbs is slowly killing the modern man, so probably keto is preferrable to the modern american diet ;) and it sounds like you eat a variety of foods - I've had friends who took the "only bacon and hamburger" approach to keto and they smelled and looked terrible. Yuck. Eat yo veggies boys!
Jesus why did I write so much?! I guess it just helps me clarify my own thoughts.
