Our survival instincts say one thing (take sides! fight back! it's us against them!). Our better instincts say another (we're in this together! united we stand!). Valerie Monroe on what it takes to turn "them" into "us."

My 17-year-old son was in a high school only four blocks from the Twin Towers when they fell. The second tower collapsed as the children were being released, shaking the ground with a thunderous rumble and sending an 11-foot-high tsunami of toxic rubble roaring toward the school. My son remembers a police officer touching him lightly on the shoulder as he began to run. “Go quickly but carefully,” the officer said.

That evening, my son and his class­mates safely home, I tuned in to a national TV newscast. Toward the end of the show, there was a clip of hundreds of children running chaotically from their school; some of the girls were crying in the melee. The scene felt distant and impersonal; I was still experiencing what I was seeing on television as somehow happening to “them,” the unlucky ones who were most directly affected or hurt. Until I saw a police officer put his hand on a child’s shoulder and say something I couldn’t hear; and then saw that child as he turned toward the camera, his young face frozen in uncomprehending fear—my son, running with the others for his life.

Since that night, I’ve never looked at a newspaper photograph of a boy in Gaza, say, or Niger, or New Orleans and not thought: He is someone’s child. There is probably a woman who cares about him with the same staggering passion I have for my son. Try this: Look at a photo of a baby wailing in hunger and imagine that it is your baby. Can you feel the queasy threat of panic rise up into your throat? You will not so easily turn the page. It took a crisis for me to recognize how quickly, how consistently and deliberately, I threw up the screen that shielded me from “them”— the Suffering, the Poor, the Unlucky, the Unchic, the Unheard of, the Unfit, the Unfunny And while I’m admitting it, the Misguided, the Manipulated, and the Stupidly and Completely Wrong. All day long, I realized, I was sorting and codifying everyone I saw: us, them, us, them, us, them. If you think about it, you might notice that you do the same.

In your defense (and mine): A study from Harvard and New York universities suggests that the impulse to identify with one group or another may be innate. We’re descended from animals that lived in groups, and survival depended upon being accepted into a group that was strong and vital, says David Berreby, author of the recently published book Us and Them. It can be deeply scary when we feel we don’t fit in anywhere; we join the sorority or the country club so that we know where we stand. The sorting is partly a way for us to figure out who we belong with and to feel, on some level, safe.

Here’s the thing about it, though: The reflexive, protective behavior that ensured our safety thousands of years ago can give us a false sense of security. Because the result is a world teeming with “them.” And we often begin to feel increasingly threatened—frightened of “them,” angry at “them,” or simply, as a way of coping with our fear, dismissive of “them,” wishing they would just go away.

I might have wished the same till the night of that TV newscast, when I found the “them” in myself. Now I see “us” everywhere, often unexpectedly, always gratefully. Keep reading for other—concrete, practical—ways to lessen the gaps, heal the rifts, and get from “them” to “us.”