I think beliefs evolve just like biology. They introduce some justification for a morality, whether it's "don't commit infanticide" or "only marry one person" or "vaccines prevent disease" or "if you rape a girl you must marry her." Certain societies rise and some fail, and the mores of culture that doesn't die off tend to stick around and be thought of as good/correct (whether they really are, or just made the cut out of chance).

I think in 500 years, accepted morality will vastly differ from what we have today.