A best-selling U.S. author who spent time with American forces in Afghanistan says in a new book that humans thrive on adversity, and that the communal way of life often experienced by combat soldiers and tribal communities is actually an “emotionally comforting” way to live.

In his new book, “Tribe: On Homecoming and Belonging,” award-winning author Sebastian Junger examines what tribal communities can teach us about a sense of belonging – a feeling often lacking from modern civilian society.

For the book, Junger looked at veteran soldiers and the sense of community and purpose that often emerges despite living through crises.

But, he says, the book isn’t just about soldiers.

“It’s about our society, and one way to understand our society is how it affects people who return to it,” Junger said in an interview with CTV’s Canada AM on Thursday.

In his book, Junger says: “Humans don’t mind hardship, in fact they thrive on it. What they mind is not feeling necessary. Modern society has perfected the art of making people feel not necessary.”

Junger, who is also a documentary filmmaker, received a first-hand look at communal life when he spent time in Afghanistan with American forces, living with a unit that could include as many as 50 men.

“They’re sleeping in the same place, eating together, doing tasks and missions together,” Junger said. “That’s basically how we evolved as humans to live, in small groups like that.”

Junger says one of the reasons many soldiers struggle psychologically when they return is difficulty adapting to civilized society.

“I think the reason is this transition to an alienating and solitary society that we live in,” Junger said. “Peace Corps volunteers have exactly the same problem, and they haven’t seen combat.”

There are many “blessings and benefits” to living in a safe and modern society, Junger says, “but ironically, there is a downside to it.”

Junger says that as affluence and urbanization increases in a society, mental health issues tend to spike.

“We have the phrase ‘To go native,’” Junger said. “We don’t have the phrase, ‘To go civilized.’”