I remember reading an article (think it was in Reader's Digest) about plants being aware of things. The researchers had hooked the plant up to some kind of a meter that registered vibrations or other changes from them. Then, they had a persson come in the room and just totally shred up one of the plants (right in front of the other plants).
After that they had people walk through the room, one at a time. The plants did not show any reaction until the "plant-murderer" walked through the room, and then all of the vibrations just went crazy on the meter.
Somehow, even wothout eyes or ears, the plants knew when one plant was viciously shredded, as well as exactly which person did the shredding.
I think that a vegetarian or even a vegan diet is probably what would be the best for us; and if we did eat meat, then it should be killed fast and humanely, and not made to suffer as it is dying.
As to whether we are designed to eat meat or not; I once read that you should look at a picture of a mutilated rabbit, and then one of a fresh apple or peach, and see which one stimulates your appetite.