Is this explained by Golding?
If you mean: 'Does [He] explain this?' within the context of the story, the answer is 'yes', but it is done metaphorically, or symbolically by comparing the behavior of the children on the island to the adult-created world from which they have come.
When the story opens the children have been evacuated from their home country because a war has begun. We will assume this is a nuclear war, or a war of such consequence that the population of urban centers are at great risk. The plane they are on goes down but not before ejecting a capsule which we will further assume has been designed for such an eventuality. The capsule, perhaps by parachute, safely lands the children on a tropical island. We can grant Golding a few liberties with the practicality of this plan ... the point is he is trying to create a setting which isolates the children from adult supervision.
Golding is careful to illustrate that these boys are not just typical boys chosen at random, but boys from a British
public (American translation =
private) school. This is a nice stroke of craftsmanship on Golding's part. The British public school system has traditionally been the educational system of choice for children from "Upper Crust" families. These schools were meant to produce the future leaders of the British government, industry and military. Golding is trying to push the case that these boys are not rowdies but are part of a class that is being processed to be "gentlemen". Another stroke of genius, in my opinion, is that Golding chose children to illustrate his point. As I mentioned in an earlier post we equate children with innocence. Children, we assume, do not yet have enough exposure to life experience to be tainted by that which we would call "evil".
What Golding is saying, loudly and clearly in this story is that even the most innocent people, when separated from the trappings of civilized society for any length of time, can revert to the primal and instinctive behavior which has been inculcated into their psyche over countless millennia of evolutionary attrition. My Grandmother used to quote an old saying from Italy:
"Children are the purest for they are the last to arrive from the hand of God." But as we get older (stray farther from the hand of God) we become corrupted by the world. In this book, as time passes, children who at first draw upon their training to organize themselves by setting up a makeshift parliamentary government and a plan of action which includes a signal fire to aid their rescue, quickly begin to revert to what we would expect of primitive cultures including the premise that "might makes right", to the invention of superstitious beliefs (the Beast in the jungle), sacrifice to evil gods to appease them (the pig head on the spike) and even to murder if considered necessary.
At the end of the book adult life appears. The adult is a British naval officer and he thinks the children have been playing a game. He is totally unaware when he finds the children that they are pursuing one of the other boys with the intention of killing him. Thus, Golding is illustrating that the "innocent" boys have reverted to, and are in fact engaged in, the same behavior as the people in the world from which the naval officer has just arrived - a world of violence and war.
If you read the book with this in mind it will be much easier for you to follow how Golding gradually strips these specially educated boys of the training they have received and the trappings of civilized life. He is making the case that our instinctive, banal propensities to revert to primitive and animal behavior lurk just beneath the surface of what appears to be our otherwise civilized psyches.