The current consensus is that groups outside the circumpolar regions typically ate large amounts of plant matter. In many groups it was even a majority of dietary calories, alongside things like honey and probably insects. This is archaeologically well-substantiated, even taking into account formation processes and preservation biases.

What is one or two best primary sources supporting your view that our hominid ancestors of one million years ago would have been eating mostly plants?

First the date: 1 MYA was the time of H. erectus, not the AMH I was referencing. That's fine, but you'll probably be unsatisfied with the evidence from the period because it's notoriously thin. Regardless, by this time our ancestors had shifted to include megafaunal hunting and harder, diverse plant foods in their diet, so H. erectus populations were likely eating both. See [1]. For a good (slightly outdated) overview of the evidence problems, see [2]. In later periods, we can discuss things like dental microwear patterns, archaeobotany, optimal foraging models, and coprolite analysis as the evidentiary bases are so much better.

Secondly, you have to understand the difference between "plants were a large component of the diet" and "carnivores". All the former means is that meat was only about 30-70% of the diet, not upwards of 90%. The exact amount would have varied hugely by group, environment, and even the season or year. The diversity of the plants eaten would also have varied for the same reasons. For instance, some groups in the Mediterranean basin in the later Upper Pleistocene were sedentary foragers who would transition to nomadic hunter-gatherers at other times.

[1] http://doi.org/10.1126/science.1236828

[2] http://doi.org/10.1086/666700

edit: overview of the elements of "forager diets" and the various viewpoints. There's also a large body of literature on archaeobotany, especially from temperate regions.

[3] http://doi.org/10.1002/ajpa.23148

My working hypothesis is that from a few million years ago to 100,000 years ago, our ancestors primarily ate megafauna (80% to 100% of calories) and so that is the diet we are most evolved to thrive off of. In the last 100,000 years, with the rise of agriculture and the extinction of many megafauna, there has been rapid selection pressure for humans to tolerate grains and dairy (and also breeding of tubers and grains to make them much more nutrition for humans). Toleration of plant and dairy food by modern people varies by race and by individual; but everyone can thrive by eating a lot of megafauna.

I am interested in evidence that contradicts this hypothesis -- particularly whether there is evidence that from 100kya to 3mya our ancestors were eating 30% or 50% or 70% or 95% or 100% plants. It doesn't seem like the links you gave me have such evidence. Got anything more convincing? The evidence from dental collagen and brain size energy requirements arguing for an ancestral diet of 80%+ animals seem more convincing to me.

We already know that the gut biome between two modern Americans can differ so greatly that a diet that makes one person obese will have no negative health impacts on someone else.

We know that obesity seems to be "inherited" to an extent, mediated by epigenetic effects.

And there are examples of populations that can extract nutrients from foods, such as seaweed, that the general human populace can't.

Heck a good friend of mine, if he follows exactly the same keto diet I do, felt physically sick and lethargic for 2 months before he gave up. Meanwhile I was out there doing 3 hour a day intense workouts.

Trying to say there is "one diet to rule them all", well, it doesn't work. Any given diet subreddit is going to be full of people for whom that diet works really well, and a self-reinforcing community will form. Back when I was super active on /r/keto people would come in and ask why it wasn't working for them, and after going through the regular checklist, I'd add "and maybe this just isn't for you!" because sometimes that is true!

I wish I had links to a study I saw where they worked to find an optimal diet for different people and were able to discover that different protein/fat/carb ratios worked well for different people. No one plan worked for everyone!

There is a lot we don't know about human nutrition, and while we can learn from past populations, holding up any one group as having an ideal diet that'll work for anyone, meh.

Heck I've seen people throw citations back and forth at each other for how good/bad cow milk is. Legit research, biochemical pathways explored and explained, and each side seemed to make some good points. None of which changed the fact that people people do GOMAD and put on insane muscle, while other people just get really bloated.

In more recent times, human diets have been under rapid selection pressure, with most human groups being able to tolerate grains, and some being able to thrive off of milk, and other human groups . These populations that underwent selection for certain diets then get mixed around a lot with various migrations, conquests, and intermarriage, and so it is a bit of crapshoot what kind of diet any given modern caucasian American can tolerate. Pretty much any American can thrive on a diet that is very heavy in cow meat, but what kind of dairy or plants can be tolerated is more random.

Heck a good friend of mine, if he follows exactly the same keto diet I do, felt physically sick and lethargic for 2 months before he gave up. Meanwhile I was out there doing 3 hour a day intense workouts.

Out of curiosity, what are the rough outlines of this diet that did not work for your friend?

Typical keto, equal portions by weight of protein and fat, with green leafy veggies on the side.

He is good at research and did his homework, just... didn't work out for him.

I didn't know there was a typical keto diet. Some people do carnivore, while some people go heavy on vegetable oils and protein powders. Was he eating ribeye steaks? Or chicken breasts and olive oil? Or tofu and almond butter?

I personally find Jordan Peterson's content pretty interesting. His daughter on the other hand, she seems pretty scammy. Have a hard time taking that diet seriously. But I guess if it makes people happy, good for them.

I was surprised to learn when my kids were born that hospital food is just about as greasy and generally unhealthy as any fast food you're likely to come across.