This is also interesting regarding to how we treat animals. If a man can live like a normal human using just 10% of his brain, then it may be possible that an animal with a small brain may be much smarter than we thought, because it uses its brain more efficient. It may actually speak and think and whatnot, but we are not recognizing it. In other words, it may not be dumber, but just different. And then the fact that we kill or enslave it it is of course an ethical issue (it is anyway).