If you like, ethical can be behavior and moral can be belief. Thus, it is immoral to want to own slaves, and unethical to own them, for the next paragraph at least, OK? So you can believe in slavery being a good thing yet not own slaves yourself, and you could own slaves and believe it was wrong too, were slavery to be common in current "enlightened" society. You can be both moral and ethical, neither, or one at a time.
All of us would agree that slavery is not to be permitted? Even though most ancient texts explain how to acquire and treat slaves and consider slavery completely normal? Including the Torah/Talmud (never could keep those two apart, they're worse than twins)/Bible/Koran?
Now, why do we agree on that? Because we have intelligence and have learned from the mistakes of the past. That is why I used the term "enlightened" earlier - we have seen the light, and it comes from figuring stuff out rather than from authority telling you how things work. Like slavery being normal.
Humans and other apes, as other primates, as any social mammal, have the same morality basis, with reciprocity (fairness) being good and deceit being punished if detected (thus, bad).

Play fair and don't tell lies (or, if you're going to lie, lie very well).

What more do you need?