I read an interesting article that basically said that our diet has to do with our blood type. Type O was the first in humans, from when we were hunters, the articles suggests that this means you need meat in your diet. Type A was second from when we started farming and they would need more grains and vegetables. Type B was third and they would need more fruit in their diet. Those with Type AB blood are the only ones according to this article that can live healthily on a vegetarian diet, at least without taking supplements.