The most vivid example of how the evil within the boys destroys their attempts at civilization and order occurs in Chapter Eleven, "Castle Rock." In this particular chapter, Ralph, Piggy, and Samneric go to Jack's fort to confront the hunters about stealing Piggy's glasses.
Holding the conch, the symbol of order and civilization, Piggy speaks to all of the boys at Castle Rock on the importance of maintaining order:
"The booing rose and died again as Piggy lifted the white, magic shell. Which is better--to have rules and gree, or to hunt and kill? [...] Which is better--to have rules and agree, or to hunt and kill?" (180)
This moment defines the boys' choices for the rest of the story; if they had listened to the logic of Piggy's speech and heard Ralph's pleas for order, Lord of the Flies could have ended quite differently.
Instead, Roger, the most innately evil of all the boys, "with a sense of delirious abandonment, leaned all his weight on the lever" beneath the giant red boulder, releasing it to strike "Piggy a glancing blow from chin to knee; the conch exploded into a thousand white fragments and ceased to exist" (181).
The murder of Piggy and the destruction of the conch signals the end of any semblance of law and order on the island. Roger's evil actions destroyed the last icon of civilization on the island. Jack's subsequent reaction confirms the hunters' savagery and abandonment:
"See? See? That's what you'll get! I meant that! There isn't a tribe for you anymore! The conch is gone--" He ran forward, stooping. "I'm chief!"
Viciously, with full intention, he hurled his spear at Ralph.
The old tribe based on trust and the ideals of the conch have been effectively destroyed by Roger and Jack's evil, violent actions.