I believe some morals are objective and all humans share them, innately, even perhaps genetically, while other morals are subjectively taught. I also believe that the interplay between these two is not fixed or categorical. There must surely be some kind of biological morality system in place as humans are social creatures and if we didn't have hard-wired reactions to certain behaviours then we would not have survived evolution.
The reason why I believe in objective morals is because I have seen group behaviours become uniform when certain states are bolstered, particularly heart centeredness. When people move out of their logic brain and into their heart brain, everyone acts the same. Where logic is not uniform and has to be taught, the heart brain is highly agreeable and aims to curb harm. Those harms and benefits are fostered by another faculty that is not categorical mind. I believe this is why most of the world's religions, at their core, talk about love and being in the heart. It's what things like the Ten Commandments are based on, and other general proscriptions about treating people well.
When a society moves out of the heart and into the logic, we need reasoning to decide why a moral has value or not. It's no longer automatic. But as we know, logic can be cruel. Some of the most intelligent logicians in the world have been fascists that killed millions. You can rationalize your way into any kind of moral system with logic. But the heart knows right and wrong without having to speak about it. You can rationalize your way out of the heart's consciousness but you can't change the truth of the heart.
Subjective morals are based on what we are taught as children (traditions) and what we agree upon socially, whether consciously or not. It's all a matter of function. They are manipulatively utilitarian to help society function. That, and the subjectivity of morals becomes more important when you enter logic. As a society, we currently value logical intelligence more than any other faculty, such that we don't believe that other faculties even exist or have relevance. So we're stuck with that for now.
In short, if most of humanity lived in heart consciousness, we would not need to have this conversation. The basic tenets of how to treat one another would be readily apparent and our laws would reflect that. Unfortunately we are a long way off from being that way as a people. I think it's rare to find people who operate from the heart level all the time.