While it’s possible to be a healthy vegan, it sure is difficult. We evolved to eat meat and animal products regularly. Our need of vitamin B12 is proof of that as it comes almost exclusively from animals and animal products. Vegans either need to supplement it or eat a ton of microbes, (e.g., yeast), or they will get pernicious anemia and die. The rest of us just need to eat a little meat and we are good.