Football player Colin Kaepernick refused to stand during the American national anthem.

And people on all sides of the political spectrum went nuts. Why?

The most obvious reason is that they either endorse or dispute his complaint:

“I am not going to stand up to show pride in a country that oppresses black people,” he said.

But there’s a deeper cause at work. It also inflames anger about other issues. If we understand it, we might be able to cool down the anger and promote social peace.

Evolution and kin selection

Animals tend to help, trust, and cooperate with other members of their species whom they see as their genetic relatives: i.e., their “kin.” Conversely, they tend to fight or flee non-relatives, who are their genetic competitors for food, resources, and mates.

Their relatives share many of their genes. By helping relatives and thwarting competitors, they get more of their own genes into future generations. That’s one of the driving mechanisms of evolution. It’s called “kin selection.”

But how can animals decide who their relatives are? They use four main cues:

• Appearance,
• Behavior,
• Location, and
• Familiarity.

Humans unconsciously use the same cues as lower animals. But we also have language, thought, and more complex social structures. Those produce changes in our appearance and behavior, affecting how we dress, how we talk, and what beliefs we profess.

We add those human cues to the biological cues we share with lower animals. We interpret all of the cues to mean that other people are our genetic relatives (for cooperation) or competitors (for hostility).

From kinship to nationality

Our small groups of genetic relatives eventually grow into large tribes or nations. Those groups are united not only by genetic kinship, but by beliefs and symbols. The beliefs and symbols hook our kin selection instincts to trust and cooperate with others who are members of our group.

Conversely, denial or disrespect toward our group’s important beliefs and symbols has the opposite effect. It hooks our kin selection instincts to perceive the deniers as genetic competitors to whom we should be hostile.

By refusing to stand for the national anthem, Kaepernick denied the validity of American symbols and the goodness of American society. To his critics, that marks him as a genetic competitor toward whom they should be hostile. His supporters react in the opposite way, perceiving him as their kin and his critics as their competitors. Both are reacting emotionally at an impulsive level, no matter who is right or wrong about America.

The same applies to many other beliefs and group memberships. They put us on “automatic pilot” toward hatreds and conflicts that we could avoid if we were thinking straight instead of letting our impulses control us.

So when we’re tempted to make blanket judgments about people or groups, we should pause for a minute. We should ask ourselves why we’re so quick to see them as enemies — and if there’s a way we can all work together peacefully.

Check out my new book Why Sane People Believe Crazy Things: How Belief Can Help or Hurt Social Peace. Foreword Reviews called it “well-reasoned and thoughtful.”