Which is what? If you leave a bunch of boys together without supervision for a few days they'll start killing each other?
No, but they bully like poop. Look at the social structures of the internet.
Also, I'm hosting a new Minecraft server for the afterschool club I work at, and the things that went on in the old children-managed one were practically bullying, albeit digitally. They actively seek ways to dominate each other, which we as adults need to show is the wrong way to go about things.
As well as cooperation & periods of peace & enlightenment.
It's funny no one ever talks about how sharing & cooperation are "human nature", only the negatives. They facts are both are both of the human animal and what will flourish more depends on what kind of society/family the child is raised in. Rape has been with mankind too since the dawn but you wouldn't shrug your shoulders & say "meh, human nature" if it happened to a loved one. Certain cultures & regions have more or less than others, same with bullying.
The following are my personal beliefs and should present themselves as challenging opinions, ready to be taken down if you prove me wrong. I'm open-minded. I will, however, note that I won't act differently at work because children do naturally bully each other, and I work my ass out to prevent it. It's at its very core social preying, which is natural for an animal like a human.
Human nature has two faces, a good and a bad one. Christianity, which is popular and relatable is a spiritual path of thought that has dealt with good and bad in humanity, inspired by Zoroaster. Civilization and savagery are two paths that are realistic for an individual to choose. In the Lord of the Flies analogy, savagery, Beelzebub, the Devil, wins. The book utilizes Christian dualist imagery which is relatable to the West, but the analogy is still true in the real world. Many things in the animal or savage side of humanity are nice, but I don't think bullying is one of them, so that's one of the savage sides I attempt to prevent.
I'm not raising the kids to be Christians, but the analogy of good and bad behavior in humans stand true, and while most of the people in a class of youngsters will grow to be 'good', there will almost always be a small portion of 'bad' people who make bad decisions on their own and do bad things to weaker children. The bad behavior must be prevented.
Unwatched without organization and civilization, bad things tend to prosper as they grow from sheer force and violence. But good is persistent because it is, well, just a nicer way of acting - generosity, kindness, helpfulness, understanding are all traits that are wished for and they should all slowly appear over time with wisdom, slowly passed down in writing and institutional control. Children don't normally have that wisdom. If not passed down from a thousand years of slow development towards a rational, good-spirited world, a child which grows up on an island really doesn't care much about his silly peers that are just hindering him in winning at Minecraft.
Although killing is a dramatic overstatement, I really don't think you'd argue that bullying wouldn't be present on an island unsupervised by adults.
Lord of the Flies isn't a scientific source of bad will seeded in humans, but I do not need it to realize that there are bad sides of human nature that are meant to be prevented in order for all of us to get along and feel better.