One moment, a mouse nonchalantly shares a cage with a cricket; the next, the rodent leaps on the insect and rips its head off—all because a scientist flipped a switch. For the first time, researchers have hacked into the part of the brain that makes animals hunt, using lasers to target specific neurons. What’s more, they’ve found this hunting center in a surprising place: the region of the brain responsible for fear. . . .Fear in mammals is controlled by the amygdala. So it is quite striking that the right sort of stimulation in the amygdala triggers the whole hunting sequence: stalking, pouncing, biting, eating. Which started me wondering about humans and our complicated emotional relationship to the killing of other animals. In many societies, the killing of an animal has been the supreme religious act, and I have always thought that must mean it triggers a range of powerful emotions all at once.