I'm going to post my reply on the thread that was started for this discussion tomorrow and it addresses our teeth. I'll also address the issue of digestive tract. Not all herbivores have complex stomachs. Those are typical of ruminants like cows who eat rough vegetation. Clearly we did not evolve to eat grass
Also, vegetarianism is very healthy when done correctly. Many vegetarians do not eat a healthy veggie diet and can have problems because of it. When a vegetarian eats a wide array of foods, such as our ancestors would have been forced to do, they will receive sufficient amounts of dietary iron.