The book Lord of the Flies attempts to show that civilization is necessary as a protection mechanism. I don't mean protection from outside dangers either. I mean protection from the group members themselves. Without civilization, the boys on the island quickly descend into a mixture of an anarchy and a dictatorship. I suppose those are two legitimate forms of civilization and government, but for the boys, it does more to destroy their group than hold it together. Civilization would protect the boys from each other, because more than likely the group whole would stamp out insurrection, or there would be a police force to do it.
Civilization also offers civilized people. Civilized people rely first on reason. They also use that reason to find solutions that benefit the group whole rather than a small group within a group. I know it doesn't always work out that way, but the book clearly shows Jack wanting power for the sake of personal gain. He doesn't care about the entire group. He cares about who he can use to get more power, and he cares about who must be eliminated. His decisions are not civilized. They are more animalistic in nature.
Civilization would also offer the boys further protection from disease. At first, this one seems counter intuitive. More people means more disease. While that can be true for things like influenza, I am focusing on sanitary conditions. Ralph attempts to get all of the boys to use the rocks by the ocean as their bathroom.
“There’s another thing. We chose those rocks right along beyond the bathing pool as a lavatory. That was sensible too. The tide cleans the place up. You littluns know about that.”
It gets washed clean with the waves and the tide, and it doesn't contaminate their drinking water. Unfortunately, nobody follows the bathroom rule for very long. Bathroom location and sewage control has always been a sign of healthy civilizations. Whether it be something as large as ancient Roman cities or small North American Indian tribes, sewage control was a priority for those civilizations.
When one views the text through an allegorical lens, it is in the rich symbolism that we find the answers. First of all, the boys each represent a different part of what we consider society by representing different parts of the "civilized man." Piggy is intelligence and reason, Ralph is government (law and order), Simon is the soul and goodness of man, and Jack is the savage nature of man. Obviously, each boy alone cannot function and survive, thus humans need the order, the soul (goodness), and the intelligence to have a functioning civilization, but as Golding points out through the fall of his boys into savagery, man cannot escape the fourth part of his nature, the id so to speak- the animalistic nature human's have in pursuit of desires.
So, there are many, many events in this work that demonstrate the importance of civilization for man's survival. When the boys become too excited about making a fire in chapter two, they end up losing a child to the fire, because ORDER was not in power.
When Piggy is shunned and treated poorly, his ideas which are by far the wisest are lost and barely escape through the path of his mutterings to Ralph, so REASON fails, and the boys struggle to work on maintaining simple tasks for survival such as gathering water and building shelters.
Also, when the boys fall into savagery and kill Simon during their hedonistic dance, the boys' GOODNESS is lost to sin and evil. Once Simon is gone, the island only falls farther away from a place one could survive. The chaos that ensues results in murder and no fire signal, which goes against hope of survival.
Without these aspects, mankind cannot function on a level worth living, one that is civilized and cultivates the non-savage part of man.