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No one likes a bully, and few things make us happier than to see someone stand up to a bully--particularly if they are sticking up for someone else. Now a new study suggests that it makes evolutionary sense for people to look out for the little guy.

In fact, our ancestors may have evolved from societies dominated by alpha males and females to hunter-gatherers to the more egalitarian groups of today, all thanks to people who formed alliances to beat back the bullies of yore.

That's because it's almost impossible to stand up to a powerful alpha male or female on your own.

"The only way to do it is by using somebody's help," says Sergey Gavrilets, Ph.D., author of the new study, which appears this week in Proceedings of the National Academy of Sciences.

Gavrilets was intrigued by one question: Why would you help someone resist a powerful group leader if this act of defiance could be downright dangerous to yourself?

Gavrilets devised a mathematical model to look at the question and found that humans are more likely to cooperate with each other against a common bully when resources are scarce. This is particularly true if a group leader's control of food and other resources is so severe that weaker group members suffer.

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"Every person wants to have access to as many resources as possible to increase his or her fitness," explains Gavrilets, professor at the National Institute for Mathematical and Biological Synthesis at the University of Tennessee in Knoxville.

"[But] under some conditions helping tendencies will evolve and that produces dramatic decreases in inequality," he says. It also gives rise to empathy and compassion.

Eventually the drive for equality ends up in our genes and transfers to how we behave culturally.

Unfortunately, bullying behavior also lingers in our genes.

"It's an echo of our past when everyone was driven to achieve higher reproductive success," says Gavrilets. "It's genetically controlled but, at the same time, we also have a genetically controlled tendency and motivation to resist being dominated by others [and] this model suggests that we probably also have a genetically controlled tendency to help victims of bullying."

Experts recommend teaching children how to stand up to bullies whether they are the target or not.

If you're being bullied yourself, the number one rule is to not bully back, says Alan Manevitz, M.D., a family psychiatrist with Lenox Hill Hospital in New York City.

First, try to ignore the bully's taunts and threats, denying them the satisfaction of a reaction, he says.

If that doesn't work, be assertive by looking the bully in the eye and telling him or her to stop. You don't have to actually feel brave to do this, just act as if you are unafraid, says Manevitz.

"It's also very important to tell an adult--teacher, principal, parent, lunchroom helper," stresses Manevitz.

The same goes if you're a witness to bullying: speak up to the bully and tell an adult.

You won't be alone.

Groups around the nation are banding together to combat bullying. The Obama administration has pledged to support anti-bullying programs and activists have started an "International STAND UP to Bullying Day," scheduled to take place on August 31, 2012.

Gavrilets' theory seems to be playing out right under our noses.

"What we're seeing right now is a number of forces combining together [against bullying]," says Manevitz.