Dumb Beasts and Dead Philosophers: Humanity and the Humane in Ancient Philosophy and Literature

Animal rights do not feature explicitly in ancient thought. Indeed the notion of natural rights in general is not obviously present in the classical world. Plato and Aristotle are typically read as racist and elitist thinkers who barely recognize the humanity of their fellow humans. Surely they would be the last to show up as models of the humane view of other kinds?