Since the dawn of time we have defined ourselves through our social groups, seeking out others that share our tastes, faith, or heritage. But what happens when we only socialize with our chosen group, and lose the ability to connect to outsiders? What happens when our tribes merely confirm our world view, rather than expand it? Traveling from the site of the Charlottesville riots to the boardrooms of Facebook, Sarah Rose Cavanagh considers zombies, neuroscience, and honeybees, as she explores how social technology is reshaping the way we socialize. Although it's not possible to turn back the clocks, Cavanagh suggests that the best answer is to shore up our sense of community.