"In the adult world, the caste system still exists in a rather potent form: dating. If you are a man who is marked out in some way as earning less"

This isn't really a caste system, it's just human nature. Women are generally attracted to men that have ambition and a good job is a good indicator of this.

Would you consider ugliness a caste system as well? Women that are less attractive will get less attention (and dates) on and offline.