Natural Selections

Review: Mama’s Last Hug: Animal Emotions and What They Tell Us about Ourselves

Frans de Waal

W.W. Norton and Company, March 12, 2019

326 pages

Hardback, $15.00


Yuriria Vazquez

Photo credit:

Can you imagine your human life without emotions? In other words, can you imagine yourself not feeling any joy, sadness, fear, anger, empathy, pleasure, or excitement? Most likely, our social world would vanish, and we might not survive since fear would no longer be elicited. Frans de Waal’s most recent book, Mama’s Last Hug: Animal Emotions and What They Tell Us about Ourselves, invites us to ponder the essential role of emotions in the lives of humans and other animals. The book challenges the notion that only humans are capable of having emotions and that it is not possible to study emotions in animals. The book is captivating, mind-changing, and a must-read for anyone interested in behavior, neuroscience, and social interactions.

De Waal is a well-known ethologist and zoologist. He is currently the C.H. Candler Professor of Primate Behavior in the Psychology Department of Emory University and a member of the United States National Academy of Sciences. De Waal begins by narrating an astonishing event involving a myriad of emotions expressed between a chimpanzee and a human. The event relates to a particular hug between a severely ill chimpanzee and a researcher. The chimp knew Jan van Hooff, the researcher, for forty years. Mama, the chimp, was motionless lying on her deathbed. When Jan entered the room, and Mama noticed Jan’s presence, she embraced him and grinned. During the embrace, Mama’s fingers patted Jan’s head and neck. A pat is a movement chimps use to quiet whimpering infants. Mama was clearly happy about van Hooff’s presence, and her patting indicated to Jan that she had no problem with him being in her territory. This event is astonishing. Normally, no one would dare to invade the territory of a chimpanzee because their outrageous strength can be deadly; the fact that Jan was able to do this denoted a deep social bond between Mama and Jan. It serves as evidence that chimps are capable of having and expressing emotions like happiness and gratitude. With this story, de Waal begins an exciting journey full of knowledge and reflections about what is known about human and animal emotions and whether it is plausible to study emotions in animals.

Over the course of the book, de Waal covers a lot of thematic ground, ranging from the expression of emotions through facial expressions and body language to different types of emotions, emotional intelligence, social signals, and consciousness in primates, birds, elephants, rodents, and fishes. The author’s narrative style is fluid, fresh, and clear. The chapters pose challenging questions to the reader by narrating experiments and their results and de Waal proposes possible answers to these questions.

De Waal challenges even the most skeptical reader and his arguments favor the existence of emotions in animals, their neural basis, and their evolution. The author defines emotion as an internal state affecting different physiological responses, such as changes in heart rate, skin color, facial movements, voice, and tears. He supports the idea that the body influences emotions through hormones, hunger, sexual arousal, insomnia, and exhaustion.

These two arguments shape a definition of emotion based on a physical substrate. De Waal identifies an explicit difference between emotions and feelings: “Emotions are bodily and mental states that drive behavior. Only when the person experiencing these changes becomes aware of them do they become feelings, which are conscious experiences. We show our emotions, but we talk about our feelings.”

By using Darwin’s definition of evolution, “descent with modification,” the author makes a case that since evolution rarely creates anything completely new, no human emotions are entirely new. This is a crucial argument to support emotions in other species, and poses an open question regarding the evolution of emotions and if they are shaped by species who depend on them for their social and survival needs.

All these arguments invite skeptical readers, like me, to think that emotions are measurable phenomena, and hence it is possible to study them in several animal species.

One of my favorite parts in this book was the section related to the expression of emotions. Here, the author does an amazing job of presenting evidence about how facial expressions in primates and body movements, such as tail movements in dogs or cats, provide a window into assessing internal emotional states. For example, we all know when a dog likes us and is excited about interacting with us. We just need to see how it moves its tail from side to side. We use similar reasoning to infer when a cat is angry. We just look at its fur and the shape of its body.

The book describes how Paul Ekman, an American psychologist and a pioneer in the study of the relationship between emotions and facial expressions, developed the Facial Action Coding System (FACS). FACS classifies facial expressions in humans based on facial muscle contractions. The book emphasizes that most of the time, emotions have ways to be expressed. To understand them, then, it is crucial to focus on the signals, the form they take, and their effect on others. De Waal himself conducted research to classify facial expressions in chimpanzees. Interestingly, he reports mixed facial expressions depending on the situation.

Other passages of the book relate to empathy. Here, de Waal describes several examples across different species, including rats, bonobos, and prairie voles. From all of the examples, one can conclude that indeed empathy is not exclusively human. In the case of prairie voles, which are tiny rodents, males and females form monogamous pair-bonds and raise their pups together. James Burkett, a scientist at Emory University, showed that if one mate is upset by anything, its partner is equally affected. This is true regardless of whether the partner is present during the stressful event.

Another mesmerizing experiment, involving bonobos, was developed by Brian Hare and Vanessa Woods. The experiment consisted of providing a bonobo with a whole pile of fruits, which he could eat by himself or share with another bonobo sitting behind a mesh door. The first thing many bonobos did was to open the door, and let the other bonobo enter. This action cost them half of their fruits. However, if there was nobody behind the door, they would eat all of the fruits immediately. This behavior provides strong evidence for empathy and pro-social behaviors. This kind of behavior is also seen in rats and elephants when they help their peers get out of dangerous situations. As de Waal puts it: “Social connectivity at its best [is] the glue of all animal and human societies, which guarantees supportive and comforting company.”

As in real life, not everything is peaches and cream. Conflict resolutions, power signals, and social organization are also part of real life and of de Waal’s book. The author focuses on social hierarchies in non-human primates and the differences between bonobo and chimpanzee societies. Crucially, bonobos are a female-ruled society, while chimpanzees are male-ruled. Both societies are hierarchical, but have very different strategies to deal with social organization. While male chimps easily form coalitions, bonobo males are not very cooperative. Bonobo females form a kind of sisterhood, and they work together in response to male harassment. This is a sharp contrast to chimpanzee females, who endure abuse and infanticide. The book reveals that brain areas like the amygdala and anterior insula, which are involved in emotional processing and social behavior, are enlarged in the bonobo compared to the chimpanzee. Studies have also shown that bonobo brains contain more developed pathways to control aggressive impulses. All this evidence supports de Waal’s point that emotions influence the way we relate to others, and thus our social lives.

One thing missing from the book is a graphical schema comparing the brains of different animals (primates, rats, birds), with the brain areas involved in emotional states. This would help readers to easily understand portions of the book involving brain structures like the amygdala, insula, hypothalamus, dopaminergic system, and so on. At some point, the author proposes to construct a taxonomy of emotions, in order to get a fingerprint of each emotion. The proposed taxonomy would be based on the areas and brain circuits involved in each emotional state. However, the author just flirts with the idea and does not develop it. This is a pity, since in recent decades, huge progress has been made in understanding circuits related to emotions like fear, aggression, mating, and romantic and maternal love, among others. A similar omission occurs when the author talks about patients with emotional impairments. Overall, the information is extremely limited in the book in terms of neurophysiological data supporting behavior.

Despite these shortcomings, I enjoyed and learned much by reading Mama’s Last Hug. The book is a masterpiece from an ethological point of view. It convinces the reader that animals have emotions and of the importance of studying them in ethologically relevant settings. I highly recommend this book to anyone interested in behavior, evolution, and neuroscience. It provides a huge amount of information but also leaves you thinking about the open questions in the research of emotions.