should be, Jack desires to disband from the group and makes his own group filled with his hunting friends. So now there are two groups one of these with Jack as the leader focusing on primal survival and the other group filled with semi civilized people that focus on shelter and being rescued. Human nature is unpredictable because anyone is capable of evil, Jack, for example, in the beginning of the story, was not a malicious person until he was willing to take a life.
Starting off, the unpredictability of human nature is what makes them capable of evil. That's what William Golding meant by "it was simply what seemed sensible for me to write after the war when everyone was thanking God they weren't Nazis. I'd seen enough to realize that every single one of us could be nazis."
At the beginning of The "Lord of The Flies" Jack starts of civilized and followed the rules of the chief and he was less like a savage but as he starts to kill pigs, he starts to enjoy it even more and soon starts to care less about being rescued and more about hunting and killing pigs.
Jack said in the story " Rescue? Yes, of course! All the same, I'd like to catch a pig first-" Jack is basically saying that being rescued is not his number one priority but instead its hunting a pig. Jack is an example on how you never know what someone is capable of like when Jack kills Simon because they thought he was the beast that some of the other boys of the island made up because of a nightmare, he says "kill the beast! Cut his throat! Spill his blood! Do him in!" Jack said this repeatedly before him and his hunter friends kill Simon. This could be what William Golding the author of "Lord of The Flies" meant by every single person could be nazis like from the quote he said, One other small example of this is Ralph, a character in the book who is the leader of everyone before Jack leaves with his group of hunters, and becomes a new group. Ralph starts off really civilized like jack but then soon starts to become more savage but not much savage as Jack
is.