It is significant that Golding's island on which the boys of Lord of the Flies are stranded seems at first to Ralph a virtual Garden of Eden. For, it was in the Garden of Eden that man first sinned and embraced the evil that found life in his heart. This "darkness of man's heart" about which Ralph weeps on the last page of the novel is the violent propensity in humanity that is deeply inherent in their character. It is an innate flaw from which there is no escape even in civilization.
After the boys are first stranded on the island, they carry with them some of the concepts of order in society. When Piggy finds a conch, Ralph, who has been elected leader, uses this conch to call the boys to meetings at which no one can speak without first being recognized and given the conch in an imitation of society. Ralph decides that Jack can remain the leader of the choir boys, who will now become hunters. However, soon the envy and cruelty of the boys causes them to separate and challenge or prey upon one another. In Chapter Four, for instance, the sadistic Roger throws stones at littl'un Henry who plays at the shoreline. However, he restrains his actions and does not harm the child because he has been conditioned by society to restrain himself because of fear of reprisals. But, later, in Chapter Eight, Roger has abandoned society and become animalistic; imitating the pig he groans and grunts. In Chapter Eleven, having by this time been liberated into savagery, Roger, with "a sense of delirious abandonment," leans upon a lever and sends a pink granite boulder onto Piggy's head, sending Piggy to his death.
Likewise, the character Jack abandons society and descends into savagery by painting a mask upon his face, stealing the rescue fire, and wreaking havoc among the boys. His hunters, engaged in a fierce ritual of pretending to beat a pig to death end up killing the innocent Simon, making him a sacrificial victim of their evil natures. Further, the hunters beat and terrorize the other boys into joining them. They chase Ralph, the final boy to be rational, and attempt to kill him by burning the island showing the deeply inherent violence in humanity.
The way in which these seemingly sweet and cultured group of English upper-class choir boys behaved upon being stranded in an island is, in itself, the biggest allegory to human nature. No matter how well-rounded is your education, how well-monitored is your upbringing, or how solid is your family foundation, one truth will always remains: Humans are still instinctive creatures that are reactive to their environment, and whose primary aim is self-preservation.
Ralph comes to mind as the character who exemplifies this paradigm: Here we have perhaps what is a model child. He has leadership skills, self-discipline, and good social skills: All those things are part of his monitored and controlled behavior learned at school and home.
However, as things become more intense and the children begin to lose their composure, Ralph has the task of protecting himself, the younglings, and especially Piggy, whom he knows is the weakest link. Yet, even Ralph himself becomes possessed by a primal and near-barbaric stupor during the pig-killing ceremony, where all the children seemed to have been taken over by their primitive nature. It seemed to have overruled everything they ever learned or knew.
Therefore, the book is clearly showing that we all have a basic make-up: We are still animals of nature, and creatures of the Earth. We are capable of both the good, the bad, or the ugly. All of us, in an equal measure, no matter where we come from.