A recent article by Tom Purdom, “The Tribalizing of America” (Broad Street Review, 7/23/13), talks about the way Americans are increasingly “sorting themselves into like-minded communities in which no one ever encounters anyone who disagrees with them about a public issue.” Summarizing a 2008 book on this topic—The Big Sort by Bill Bishop—Purdom surveys various symptoms of the phenomenon, not just the obvious example of politics but also the manifestations in living arrangements (“Liberal Democrats … prefer denser, more urban communities”) and religion (“Democrats go to one church on Sunday morning, Republicans to another”).

Why is this pattern so dangerous? We know from sociological studies that “Like-minded groups tend to move toward the extremes.” As time passes, the groups will have less and less in common and be more inclined to mutual distrust—not that they will often encounter each other except on the TV news, but on the rare occasions when they do cross paths, they’re more likely to have a Trayvon Martin–George Zimmerman kind of confrontation, unhealthy for society at large as well as for the individual participants.

Purdom cites technology as one factor in our increasing tribal isolation. “Like has always attracted like, but modern technology has made it easier to form tribes. Church shoppers can sample churches scattered through an entire metropolitan area, thanks to the automobile. The Internet and cable TV offer access to a kaleidoscope of information and opinion, but they make it easier to filter out sources that make us uncomfortable.”

I began to muse about the origins of this trend. Though I haven‘t read Bishop‘s book, I did check out his website, where he traces the changes to about 1965. Sometime around then, statistics suggest, broad-based, “mainline” institutions (such as traditional churches and Elks lodges) began to decline as people migrated to more specific, “targeted” groups (evangelical churches, Common Cause). Was that really the beginning, though? The John Birch Society was founded in 1958, the Campus Crusade for Christ in 1951—organizations that seem to fit Bishop’s model.

In looking for social origins, I’d go back even further than the 1950s, as Purdom does in mentioning the automobile as a contributing technology. And I’d go beyond America’s borders. After all, the violent 20th century was dominated by clashing far-right and far-left ideologies like fascism and communism, and the reaction to them. We’ve been tending toward extreme groupings for a long while now, perhaps ever since industrialization gave the working classes cause to get angry.

What’s new, definitely, is the efficiency with which we can sort ourselves. With cheap assault weapons, militias can ethnically “cleanse” entire regions. In suburban environs, gated communities can keep the neighborhood pure. The Internet allows new meeting points for those who detest Republicans, Obamacare, Israel, Hezbollah, or the new royal baby, His Royal Highness Prince George Alexander Louis of Cambridge. (Actually, I don’t know of an anti–Prince George site, but I’m sure one will pop up soon.)

What’s also new, or old, is our reliance on religion for much of our sorting and other-hatred: Islamism (itself splintered into mutually intolerant sects), the fervent Zionism of the Israeli settler movement, the rise of radical Buddhism in Burma, etc. When Yeats asked in 1919,

         what rough beast, its hour come round at last,
Slouches towards Bethlehem to be born?

it seemed he was imagining a new theology that might arise with the turn of the millennium. Instead, lacking imagination, we’ve returned to the ancient faiths to animate our divisions. We could create a novel creed, but that would terrify most of us, especially if it implied we should let others in instead of keeping them out.