The best discussion of moral progress I've seen yet is in Heinlein's Starship Troopers, where morality progresses by becoming more inclusive. Once, it was family, everyone else was fair game; then, tribe, race, religion, nation, now we recognize (at least officially, there are still many on lower "rungs") the human species as being deserving of our consideration. In Starship Troopers, Heinlein had one of his teachers in "History and Moral Philosophy" say that they were developing morality for dealing with intelligent aliens.

For the counter position, that morality is delusion and fraud, L. A. Rollins, "The Myth of Natural Rights" and the extended discussion by R. A. Wilson, "Natural Law", are well argued and entertaining.