For the many animal species that live in small, independent social networks (apes, wolves, whales, etc.), outsiders are typically dangerous, feared adversaries. Survival for such animals, therefore, requires not just the relative safety of one’s own group, but also a well-tuned ability to identify nonmembers.

Likewise, for millions of years beginning with humankind’s earliest communal framework — isolated, close-knit clans of hunter-gatherers — contact with strangers often meant capture, injury or worse. Accordingly, evolution over the ages gave humans our hard-wired tendency to fear and devalue “others.”

Relatively recently, around 70,000 years ago, abrupt and remarkable changes (by evolutionary standards) in the brain’s prefrontal cortex facilitated vastly more complex human thought — not least the concepts of empathy and compassion. These developments, in turn, helped pioneer peaceful interaction between disparate, often rival groups. More refined collaboration, meanwhile, ultimately enabled humans to spread across the planet and become Earth’s most influential species (as well as the creators of our modern, global existence).

Mutually beneficial exchange — bridging divides both great and small — has always been the cornerstone of humanity’s triumphs and progress. Frustratingly, though, this capacity to transcend ethnic, national, social and cultural lines still struggles to overcome humankind’s default suspicion of differences.

In fact, attitudes of societal divisiveness (which originate in the brain’s extremely primordial amygdala — our “lizard” brain) can still easily overwhelm our much newer inclinations toward tolerance and cooperation. Thus, forever sabotaging progress and pulling forcefully in reverse is that deeply ingrained “tribal” instinct — our tendency to categorize people as similar (by any number of criteria), thus worthy, or dissimilar, unworthy and perhaps even threatening.

As if not enough, tribalism’s intoxicating, addictive allure has long been used by those who seek to weaken, control and dominate others: First, divide. Then, conquer. Indeed, is there any conflict in recorded history that didn’t originate from, and become worsened by, such fear and disdain? Despite our more evolved modern instincts, humankind’s innate propensity to shun and dehumanize unlikeness continues to be our single greatest enemy; from tribalism, all other challenges descend.

What to do? Foremost, try to identify tribal attitudes wherever they exist — in our own lives, plus in our communities, nation and beyond. Next, imagine these fears and prejudices as a series of raging fires.

Finally, to address the smoke, flames, searing heat and loss, would you suggest reaching for gasoline? Of course not! Yet tribalism may as well be an oil tanker. Thus, if for nothing but your own success and advancement (and for that of your family and friends), please help relegate humankind’s self-destructive, archaic tribal tendency to evolution’s trash heap.

Only collaboration can advance our lives and communities, plus the nation and planet, in ways that we all need and desire.