Should? Why should? Was the new version always better, and we just didn't know it? If so, there must be a common standard by which to judge -- and it is this standard which I mean when I say "morality". Please tell me which standard this is and how we may discover it with more specificity than you did above, since the meaning of experiences and conditions must be interpreted and understandings must be reached validly.
Also, please tell me if the rule against child molesting is, in principle, up for grabs based on "new understanding". And who decides.
Human beings seem to be genetically designed to try to get as much as they can but to become jealous if others obtain what they do not have. Morality is an attempt to limit both behaviors so that a society can function.
No, that's not what morality is. That's what law and social convention is. Morality stands over law and conventions and lets us judge them wrong and conclude they ought not to be as they are.
Sometimes. Sometimes you may genuinely care about the other person. Why? Well, that's part of your genetics. You might as well ask why you feel anything. Why you have two legs and not three.
I could ask what if I'm a sociopath, but as it happens I'm not. I do care about others. But this has nothing whatsoever to do with morality. It is observation. Morality says I should care; if I actually do, well and good, if not, I ought to change.
So far no society and no morality have yielded a perfect world...so people experiment. Sometimes the new is better than the old, sometimes it isn't.
Please tell me which standard this is and how we may discover it with more specificity than you did above
I can't.
Also, please tell me if the rule against child molesting is, in principle, up for grabs based on "new understanding". And who decides.
In a sense it is since different societies (and the same society during different periods) decide what constitutes child molesting...and they don't always make the same rules.
Obviously, the people who make up the society decide what is right.