I argue all sentient things have moral status. We cannot exclusively value our humanity. If we only valued our ability to rationalize, then infants and certain types of people with disabilities would not be given moral status. Our morality is concerned with whether or not the collections of atoms to be affected by an action can be hurt or helped by that action.
It seems we assign moral status to that which can suffer. We do not concern ourselves with moral questions about a rock, because a rock cannot feel pain. But we concern ourselves with the rights of people and animals because they can, and do feel pain. It is this consideration of suffering from which humanistic morality is derived.
I like this morality. It is one concerned with empathy—the main thing to be considered when debating over moral questions. I believe all that can suffer to hold moral status, and all that holds moral status holds a right to object to treatment that causes it to suffer. To respect the rights of a moral status is the least one can do when he asks that these same rights are to be respected when they concern him.