Sweet memories, however, don’t really explain the degree to which humans crave sugar, or the way sweetness holds us in its thrall. To understand this captivation, we need to look deeper into the past, when a taste for sweets was more advantageous and calorie sources were far less abundant than they are for most of us today. Our ancestors needed to differentiate between sweet foods that promised a high dose of energy—fast calories for survival—and foods that tasted bitter, and were more likely toxic. And so we adapted accordingly. Our positive response to sugar is thus hard wired: when given a sugar solution, newborns put on a happy face (see the photo accompanying the “Sweetness Preference” article). Gazing deep inside the brain, as today’s technology enables us to do, we can actually see our reaction to sugar: the same parts of the brain light up for sugar that light up for cocaine. No wonder craving feels addictive! We are hardwired for pleasure, too, a characteristic that inevitably inclines us toward excess and extravagance.