It seems worth thinking about it in the context of the evolution. To kill other members of our species limits the survival of our species, so we can encode it as “bad” in our literature and learning. If you think of evil as “species limiting, in the long run” then maybe you have the closest thing to a moral absolute. Maybe over the millennia we’ve had close calls and learned valuable lessons about what kills us off and what keeps us alive, and the survivors have encoded them in their subconscious as a result. Prohibitions on incest come to mind.

The remaining moral arguments seem to be about all the new and exciting ways that we might destroy ourselves as a species.