This is actually a fairly difficult question to tackle. I would say self-awareness and the abilities to reason, learn, and teach. However, many other animals have some of these qualities. I suppose it is unique that we are able to foresee how present events will impact the future and plan accordingly. Really, I don't think that being human is all that special. Most other creatures have adapted very well to their environments. We continue to evolve because we can't seem to find a balance with nature.