Gattaca shows that catergorising people into a hierarchy of castes ("superior" and "inferior") is both false and dangerous. How does this relate to real life?
Don't forget feminism in thinking about a superior/inferior caste system. In the movie Gattaca, people were treated differently based on things they couldn't control-- whether they had natural genetics, or superior, altered genetics. Similarly, we cannot control our race or our gender, but our society CAN control how we treat people with such differences equally.
If you have ever read The Giver by Lois Lowry, you can apply the lessons in Gattaca to that book as well. In The Giver people are given jobs based on their ability and there is a very rigid, and widely accepted, caste system.
What is more ethical about their caste system than ours, or the fictional one in Gattaca, is that their rankings are based on ability, and not on things that are out of a person's control. They are ranked in society by the skills they could perform-- if we are going to rank people, the lesson we could learn is that we should base our rankings on ability and not race, gender, etc.
Well before in the 1800's or so in Latin America the european conquistadors invaded and set up caste systems similar to what you have described. In fact they had a way more complicated system that determines what kind of quality one is depending on if you were "pure" Spanish or mix. This can determine your future in terms of what you do for a living and how well off you will be.
Similarly, in the US immigration today uses stereotypical systems to choose what types of immigrants they want to enter into the United States.And when a time comes where immigration is limited they only let those people in that they believe are of a better quality i.e. no Mexicans because they are lazy. Obviously you can't back these up with facts and tons of literature because its done overtly.
And the biggest example of this is slavery before the civil war.