This civilization began around 400 years ago after a war broke out.  The cause of the war was a corrupt aristocratic class so in the post-war era the people decided to establish a government for the people where the most common people rule.  The original 30 "Specters" as they are known were elected by the people on the basis of how average they were.  The original 30 were seemingly the best fit for the job of being the most common and so they led the people to prosperity.  Every year after the original election a single 18 year old was selected from the population by the 30 "Specters" for training.