Many readers see Lord of the Flies as Golding's statement on the nature or state of mankind. By stranding the boys on the island without the presence of adults or any real sign of civilization, he creates an experiment in "man" in his natural state. The society created by the British school boys becomes a microcosm for society at large. Although the children attempt to establish roles of responsibility and rules of conduct, without the constraints of civilization, their fragile society falls apart and chaos ensues.
Without the rules of adults, school, and general mores of a civilized society, the boys turn on each other. They destroy the symbols of order- the conch shell and Piggy's glasses. They kill Simon and Piggy and are hunting Ralph when they are rescued at the end of the novel.
The final irony is that the naval officer who rescues the boys is himself (along with his whole country) at war. Golding seems to be saying that mankind can't help but turn on and destroy itself.