On his website, Sebastian Junger ’84 writes that his latest book, Tribe: On Homecoming and Belonging (Twelve, May 24, 2016), is "about why tribal sentiment is such a rare and precious thing in modern society, and how the lack of it has affected us all. It’s about what we can learn from tribal societies about loyalty and belonging and the eternal human quest for meaning. ... Humans don’t mind duress, in fact they thrive on it. What they mind is not feeling necessary." On May 21, Scott Simon, host of NPR's Weekend Edition Saturday, invited Junger to discuss the origin and…