Primatologist Frans de Waal uses the character of Mama, an elderly female chimpanzee, and her relationship with a human scientist, Jan van Hooff, as an entry point into his larger exploration of emotions in nonhumans, especially primates. De Waal guides the reader through the evidence that other animals primates have emotions as well. He includes anecdotal evidence and quantitative data from empirical studies. When Mama neared death, she and van Hooff, who had known each other for forty years, shared some moments of physical closeness. One day when van Hooff visits her, she is sleeping; when she wakes up and sees him, she

expresses immense joy at seeing Jan. . . . Half of Mama’s face is a huge smile while she yelps—a soft high-pitched sound for moments of high emotion. In this case, the emotion is clearly positive because she reaches for Jan’s head while he bends down. She gently strokes his hair then drapes one of her long arms around his neck to pull him closer. . . . [H]er fingers rhythmically pat the back of his head and neck in a comforting gesture.

The occasion was remarkable not only for the affection she showed to Jan, but because it was the first time in their lives they had not been separated by the cage’s bars. Humans do not enter chimpanzee enclosures at the zoo, but he is allowed the risk because she was so near death.

Much of the book is an overview of several decades of research on emotions, a quality which many consider human beings to have a monopoly on. De Waal shows that considerable research indicates that this narrow view does a disservice both to humans and our fellow primates. For many decades, it blocked research along paths that are likely to provide a more nuanced understanding of just how different people really are. He speaks sharply of such classification as “linguistic castrations.”

By boiling down everything animals do to instinct or simple learning, we keep human cognition on its pedestal.

De Waal presents a concept called “anthropodenial,” his term for the human tendency to insist that humans are exceptional, even in the face of evidence to the contrary. He consistently challenges the ideal of clear dualism between humans and all other animals. He takes issues with the common argument that locating emotions in nonhumans is projection and that we see what we hope to see in animals being studied.

The anthropomorphism argument is rooted in human exceptionalism. It reflects the desire to set humans apart and deny our animality. To do so remains customary in the humanities and much of the social sciences, which thrive on the notion that the human mind is somehow our own invention. I myself, however, consider the rejection of similarity between humans and other animals to be a greater problem than the assumption of it. I have dubbed this rejection anthropodenial. It stands in the way of a frank assessment of who we are as a species.