Help with an essay introduction regarding Lord of the Flies?

The essay topic is "What are some of the reasons suggested by Lord of the Flies that evil triumphs over good?" So far I want to incorporate that evil triumphs over good through basic human nature if not held in check by the confines of society. Humans are naturally destructive and savage. Now don't go saying that your not going to be doing my homework for me or w/e i just really need a good grade on this and I could use some help. I appreciate any help or tips.