Technically, homo sapiens evolved to be omnivorous, with our earliest ancestors being hunter/gatherers. It's in our DNA to have a need for animal protein along with vegetation. Even vegetarians and vegans have to find ways to supplement it in their diet.

To be more precise, our larger brains are product of evolutionary needs and branching out from diets of simple fruits and vegetation, which give our bodies moderate energies, to adding animal protein in the mix, which boosts our energies to allow for a larger brain capacity. Our brains are quite larger than our evolutionary cousins, the chimpanzee, and even they form hunting parties to go out and hunt down meat.

Actually, it's quite fascinating. The males in a family group go out and form a hunting party, where they hunt down small mammals, usually small monkeys being their preferred choice, and they give some of the meat to the females in their family group, who remember them and allow them to father the next generation with them later on. Sometimes, though rarely, they even hunt down members of their own species, in another, bordering family group, which has usually tested the males to their tipping point and all and all out war happens between the males.

As for growing crops, the pollutants from the fertilizers alone is more damaging than the methane producing live stock we consume. Haven't you learned nothing from the DDT disaster that nearly wiped out the American Bald Eagle? If you were to argue that say, organic fertilizers were the way to go, you'd need livestock to produce said fertilizers, right? It's a catch 22 if you ask me.

I could go on and on about how audacious your ideals are, but then again, I would be preaching to mute ears, much like you are right now with your vegan/vegetarian viewpoints. With that said, I have a hankering for a nice hot, juicy sirloin steak, dripping with all it's deliciousness. Thanks!