You are a caveman, wandering the land some 15,000 years ago. Your tribe is not much different than any other. Each of the members of your clan has a unique personality... not much different than nowadays.
One of the guys, Thog, is kind of ... off.
- He is the one that if you come across a herd of buffalo, will kill three extra, even though you don't need to.
- He is the one that will try to break your spear when you aren't looking.
- Speaking of spears, he tries to take the spears away from other tribe members - he doesn't feel they are "qualified" to carry a spear.
- He is the one who clubbed to death the dogs that your tribe had kept for years. He said they were acting aggressively toward him. You don't think so.
- He is so insanely aggressive on things that your tribe decides to put him in charge of "security" - the plan being, if attacked by another clan, you send Thog out first to meet the threat. He will either kill the threat or die trying, and either outcome is OK with you.
Of course, Thog lives today. Usually, we call people like this "police officers." They kill dogs, bully (and kill) people, and generally are not of a high IQ.