I chalk much of the varieties of human behavior up to the idea that there are several different ethical paradigms that individuals progress through their lifespan.
One of the distinguishing features of this progression suggested by a variety of researchers, Perry, Kohlberg and Gilligan come to mind, is a gradual universalization of identity. This change in identity has both personal and interpersonal repercussions generally leading to more humanistic positions.
Progression, however, is necessarily a function of identity alteration, which, depending on the chemistry and life experiences of the individual, may be unlikely to take place.
It's certainly an interesting question to contemplate and I like your inclusion of Taoism. So far as religious systems that impose a minimum of structure on the interpretation of experience, it's hard to beat.