It has been said that the primary difference between humans and other animals is intelligence. By far, human beings are more intelligent than other animals--yes, even dolphins (who haven't the wits to avoid tuna nets).
According to this logic, then, the more intelligent the man, the more human he is.
While intelligence is a huge difference between humans and other animals, it is not the only thing--or even the most important thing--that sets them apart.
Human beings know the difference between good and evil. Blame it on Adam and Eve (especially Eve) if you like, but we've eaten from that tree, and we know.
When a bear kills a man in the woods and eats him, that bear should be considered dangerous, but no one calls the bear a murderer. When a man kills another man in the woods and eats him, that man is considered more than dangerous. He is a murderer--and even worse (what with having eaten his victim and all).
This is why ignorance is bliss. If you don't know the difference between right and wrong, then you are not accountable for your actions (or at least not as accountable).
Combined with the intelligence factor, we come to this. The more intelligent the human, the more good or evil he may be depending upon to what he sets his mind.
No one whom I know questions the intelligence of Barack Obama. However, its what he plans to do with his intelligence that will define him as a man.
For that matter, I tremble.