to imagine butchering human bodies. Like so many simple claims that go unchallenged, we should be puzzled by this one. We should ask: what’s normal? The evolutionary history of each species’ brain does not provide a complete account of what the brain can do. Consider again a topic from chapter 1: domesticated dogs and their ancestors, the wolves. Though dogs live with humans, and are often raised by them, they never acquire a human language. In this sense, the domesticated dog is just like the wolf. But what dogs can do, with greater facility than any wild wolf, is understand a variety of human gestures such as pointing and the movement of our eyes. This capacity emerged following a period of human domestication. Wolves were not part of this selective regime. But, and this is the most interesting twist in the story, wolf puppies raised by human caretakers develop into adults that can read pointing and looking extremely well. This tells us that even wolves evolved the potential to read human gestures, but only human environments favor this skill. This tells us that what animals express is not necessarily indicative of their potential. To uncover their potential, we must alter the environment or wait for such changes to happen naturally. When we ask What's normal), we are asking two questions: what is the evolved repertoire and what is the evolved capacity? The evolved repertoire tells us something about the relationship between a species’ biology and the environments that have shaped their behavior. The evolved capacity tells us about a reservoir of behaviors that may only emerge in novel environments. What’s normal human behavior? The same distinctions apply to us as to dogs and wolves, with the extra complication that our species adds because of historical twists and turns orchestrated by legal, political, ethical, religious, and medical points of view. History presents us with hundreds of cases where an accepted normal mutated into abnormal, or where abnormal t