That's called sentience. The ability to make a conscious decision based on the outcome of events. Where many animals have instincts, humans have none, however conversely we have conscious thought. A lion doesn't plan his actions a week in advance, nor does he comprehend the longterm consequences of his actions. One wonders if our sentience, however, is truly a gift and not a curse. Perhaps it is the remainder of the animal kingdom which are superior to us and not the other way around. What luxury it must be not to worry about future events and exist only in the now.

Still, if one accepts the fact that we are omnivores, it stands to reason that our biology demands this sort of nutrion, irregardless of personal belief. I'm not suggesting that one MUST eat meat (indeed, as indicated before, I'd return to a vegetarian state, myself, if I could do so with my health still intact). This is just some food for thought and I'm really only thinking aloud at this point. But if humans' brains advaced as a result of eating meat -- as is evidenced by our fossil remains -- wouldn't that mean that if ALL humankind were to revert to an herbivorous lifestyle we would eventually, over the millenia, develop back into less intelligent life forms, incapable of the modern feats accomplished today (use of tools, premeditated thought, thinking ahead, etc.)? It may be a bit far fetched of an anology, but there's some sense to it..