I think there is some evidence morality improved, one as a thought experiment, another as a real, factual evidence.

The thought experiment is considering that you would take someone from now, and teleport him back to another period of history (say the Dark Ages, or the Roman Empire), and in the other way, take someone from those time and teleport him to now. In both cases the person will be shocked, and need time to adapt. But I do think there will be a significant difference : the guy from now teleported to the Dark Ages will be horrified that they use torture and horrible punishments, the one teleported to the Roman Empire will be horrified about gladiator games and slavery. The guy from the past teleported to now will not be horrified by the lack of them, but surprised that we manage to do without them : how can you maintain civil peace and order without cruel punishments ? How can you feed people without slaves ? How can you entertain people without gladiators ? That's a fundamental point to me : many things which are unethical now were accepted in the past not because they were valued for themselves, but because they were perceived as the only solution to a worse problem. The same apply with corporal punishment in education, or countless other examples. And the same will apply to things like prison in the future : right now, most people don't support prisons because we love putting people in cage, but because we fear (rightfully or wrongfully) that without prisons, there would be much more criminals.

The real experiment is showing how (more or less) isolated cultures adapt to the modern world. They very rarely are horrified by most of what we consider "moral progress". They adapt quite fast to the modern world. That's something Darwin described quite well in his travel logs, and is not limited to him.

Sure, there are things which can horrify people from the past - the way we treat the elderly in modern western societies by "locking" them in pension house instead of keeping them with the family as done traditionally, for example. Or things like porn which can horrify some, mostly for religious reasons. But those are a minority.

But apart from this disagreement, upvoted for asking interesting questions in a novel way.