Why should we imagine this world? We have no reason to believe it can exist. People are basically chimps, but just past a tipping point or two that enable civilization.
We'd also have to agree on what "behave morally" means, and this is impossible even at the most basic level.
Usually "behave morally" means "behave in a way the system ruling over you deems best to indoctrinate into you so you perpetuate it". No, seriously, that's all there is to morality once you invent agriculture.
We'd also have to agree on what "behave morally" means, and this is impossible even at the most basic level.