To what extent does Shakespeare in Romeo and Juliet explain the origin and nature of prejudice and its effects?

Shakespeare shows the true nature of prejudice by not
explaining its origin.  We don't know specifically what happened between the two feuding
families.  We only see they are prejudiced against each other.  This is frequently the
way prejudice works in the real world; people might not know why they feel a specific
prejudice, but they still follow it.

Shakespeare goes on to show the
depths of this prejudice in the many fights and violent acts between the two groups.  We
see this type of hatred displayed between the characters Romeo and Tybalt or Benvolio
and Tybalt.  We even see evidence of this prejudice between Romeo and Juliet when they
first meet.  Juliet says "my only love sprung from my only hate." 

We
see the effects of this prejudice clearly throughout the play.  One example is found in
Tybalt's unwillingness to turn from violence.  Romeo attempts to diffuse the situation
many times, but Tybalt will not forgive the perceived offense.  Eventually, Romeo and
Juliet pay the ultimate price for the prejudice of their
families.