Good points. I think those are legitimate possibilities. A part of me feels that humans have always consumed "some" amount of animal products. But certainly not to the excess of todays standard American diet. And todays methods of providing animal products for consumption are of great concern. I don't approve of the way it is done.
Then there is the nutrition aspect of it. B12 from a pill is not the same as B12 from animal products. So I think I am still eating small amounts of animal products for the insurance of the B12 that comes from a source we have been getting it from forever. I think if I can convince myself that this is not a valid concern, it could bring me closer to saying "What am I waiting for? No more animal products".
So that is something I have to clear up. I think subconsciously my concern is that I might be depriving myself of a "required nutrient" in it's "natural state"....
You just exposed your limiting belief that making you keep that 10% habit. Your subconscious mind thinks "you need B12 from animal source and that humans always consumed some animal Products". So the way to break a limiting belief: First step would be to create doubts in that belief. Second step would be to create a new belief and reinforce it with personal experience.
Why does it matter to you if humans consumed some animal products? Maybe they did but very rarely. Just think about the energy investment needed for hunting. There are many theories that say hunter gatherers were mostly gatherers. And after the beginning of the agriculture era they were be able to grow lots of food and store it so why waste time on hunting. Also there are some evidences for populations that were totally Vegan and lived without Animal Sources. There is lots of info you can find about this online.
Animal products today are far apart from being Natural. There is lots of pollution in our seas. And fish are full of heavy metals like mercury. animals eat lots antibiotics and who knows what with all the GMO.
Is it really so natural getting B12 from animals? Why do you think so cause that's what they tell you?
animals are NOT producing B12. It's produced by Bacteria. It just that animals eat foods that are contaminated with it. Humans today are far from their "Natural state". Humans in the past didn't live in houses, didn't eat processed food, didn't sit in front of a computer, didn't watch TV, did get lots of sun, did lots of physical activity... you get the point.
Before the sterility era we were living closer to the ground just like animals. So that's how we got our B12. So to be really natural is to go back to living in a tent without washing your hands.
I can point you to some online links if you need more info.
One last thing, at the end its all a matter of your own choice and experience. I don't think you can know for 100% what happened in the past.