In the most basic terms, bullying is about dominating – and we come from ancestors who were big into the dominance hierarchy. As Christopher Boehm, PhD, who literally wrote the book on it (Moral Origins), says, “Any species that has a social dominance hierarchy, like apes or monkeys or wild dogs or lions, has bullies.” He adds that bullying is adaptive for many species (and even for us, in many ways), “because you get better food or mating opportunities…

In primates, studies have shown that the top bullies have more offspring and therefore their genes proliferate.” So there’s a clear payoff to it, since the more you bully, the higher you’ll rise in social ranks, and the more offspring you’ll have. This may have worked for us in years (or eons) past, but nowadays, bullying is not so adaptive.

The problem with evolution is that doesn’t occur evenly. We develop extraordinary skills in some ways – abstract reasoning, language, and even social interaction – and in other ways, our behavior is breathtakingly outdated. Ancient parts of our brains still exist, and inform our behavior in lots of maladaptive ways. Bullying is a great example of this.

via Bully Psychology: Where Evolution And Morality Collide – Forbes.