> Morality applied to humans wasn't universal either.

Yes it was. Always. It's just that morality, being a human invention/illusion, varied from culture to culture and from era to era. Your examples ( slaves, caste system, etc ) isn't a lack of morality or non-application of morality, it's just different morality applied in different cultures. India has/had morality and the south has/had morality, just different morality than we do today in the US.

Regardless, morals can only be applied to humans. Try to apply it to animals and you get nonsense. I asked basic questions in my comment. If an elephant has 'moral weight' then killing it is wrong. So must we arrest and prosecute lions who kill elephants? Do we arrest everyone working for national geographics for profiting off of snuff films?