Stop bullying: It’s not just a public service slogan, its an evolutionary rallying cry.

As a national campaign urges parents and children to stand up to bullying, a biomathematician at the University of Tennessee says the urge to band together against strong aggressors is a key to humanity’s success as a species.

In a study published Monday in the Proceedings of the National Academy of Sciences, Sergey Gavrilets uses mathematical models to investigate just why humans exhibit strong egalitarian, or socially equal, behaviors.

He concludes that by standing up to bullies and preventing them from monopolizing resources, groups could increase their odds of survival and produce more offspring. In the process, people evolved a genetic drive to help weak individuals fight back.

Read more at LA Times.