For more than 30 years, bestselling author Sebastian Junger has been haunted by something told to him by a close friend who is half Lakota, half Apache. “My friend said, ‘You know, it’s a funny thing that on the frontier the white people were always running off to join the Indians, but it never happened the other way around.’ That just sat with me my whole life.”

He was reminded of that remark several years after he was imbedded with a platoon of U.S. soldiers in Afghanistan. “I was thinking, why is it that so many of the soldiers I was with did not want to go back to the United States? And why did so many of them miss the war? Suddenly I had this flash of insight. Oh, my gosh! It’s the same thing—it’s why the white people who joined the Indians didn’t want to go back to society. The soldiers don’t want to go back to modern society. Everyone’s actually happier in a communal situation, even if it’s in an adversarial situation filled with hardship; living close together and being reliant on each other is intoxicating, and no one wants to leave it.”

He explores these ideas further in his latest book, Tribe: On Homecoming and Belonging (Twelve, May). Once he had that awareness about the pull of communal living, he made another observation. “I thought, maybe that’s the explanation for these incredibly high levels of post traumatic stress disorder for people coming home from the wars who didn’t even see any combat. Maybe the real common denominator is the trauma of re-entry into modern society from a communal experience.”

Another aspect of tribes that the author explores is what happens in contemporary society after disasters. He looked at suicide rates and psychiatric hospital admissions following such things as the London blitz and the siege of Sarajevo, and saw them decline. He notes, “The theory is that when society is assaulted in some way, class structure breaks down, class differences disappear, people come together—they need each other. All of a sudden, people are sheltering in basements. It doesn’t matter if you’re a stockbroker or a garbage collector, everyone’s equal. And that has an incredibly positive effect on mental health. So mental health problems actually decline during times of chaos, violence, and destruction. Disaster returns us to the kind of small unit society that is exemplified by our evolutionary past, which is obviously what we’re wired for and which in some ways make us happiest.”

Junger will be taking up this topic as one of the speakers at the Adult Author Breakfast this morning and will also discuss the role of books and reading in his life. He will sign galleys afterward in the ABA Lounge. If you miss him there, you can catch up with him later this afternoon signing galleys at the Hachette booth (1716 ), at 2 p.m.

This article appeared in the May 12, 2016 edition of PW BEA Show Daily.