The ideal Utopian society.
In one of Plato's books, The Republic, Plato describes the ideal Utopian society what it would take to bring upon such a world. As all of his books are, The Republic is a Socratic dialogue that is concerned with justice, and the order necessary to make a closer to perfect society. First off, Socrates believed that the "guardians" (rulers), "auxiliaries" (soldiers), and "producers (workers, artisans), would make for a perfect society.
Females and males should be educated in the same ways and be able to have the same political power. For the guardians, sexual intercourse would be designated for certain times of the year, and the pairings would be determined by others. All the children produced from these pairings will be taken away from the parents and raised together so that parents don't know which offspring are theirs. Any children produced outside of the designated intercourse would be killed. Unlike most societies, where people mostly cared about their own families over society as a whole, people in this Utopia would see everyone as part of their family so that there are no divided loyalties.
Though Socrates sounds insanely idealistic, he was trying to set the template for a more unified world that would keep harmony and peace for all people, and help them to lead happier lives.