Our brains evolved for an environment very different from the one we currently inhabit. As a result, we carry all kinds of biological baggage. Humans are still primed to detect threats and dangers that no longer exist—think of the cold sweat when you're stressed about money, or the fight-or-flight response that kicks in when your boss yells at you. Our safety is not truly at risk here—there is little danger that we will starve or that violence will break out—though it certainly feels that way sometimes.