Mama was nearing the end of her life when the researcher Jan van Hooff visited her at the chimpanzee’s colony at Royal Burgers Zoo in Arnhem, the Netherlands. At 59 years old, she was quite elderly, even for a chimpanzee. Although Mama and the van Hooff had known each other for many years, the chimpanzee initially did not recognize the researcher. When she finally did, her smile could not hide her happiness. Sensing van Hooff’s sadness, the chimpanzee hugged him. This would be Mama’s final hug. She passed away a week after their reunion.

To many, it may come as a surprise that a chimpanzee can display empathy. Some may even question whether the scene described above truly shows it. However, we now know that primates’ emotions are not so different from ours. Chimpanzees, like humans, exhibit generosity, gratitude, justice, grief, forgiveness, consolation, and friendship—feelings that were previously attributed exclusively to humans. And if we now understand that animals possess such emotions, we largely owe it to the work of a Dutch primatologist: Frans de Waal. Sadly, the renowned scientist and best-selling author passed away on March 14 in Stone Mountain, Georgia, at the age of 75.

Born in the city of 's-Hertogenbosch in the Netherlands in 1948, de Waal showed a keen interest for animals from a young age. This enthusiasm nonetheless waned after an uninspiring introduction to biology in high school, leading him to consider studying mathematics or physics instead. It was his mother who, aware of his passion for animals, persuaded de Waal to study biology at the Catholic University of Nijmegen.

De Waal’s first contact with primate research came from a lucky coincidence. The psychology department, where he spent time to earn extra money while at college, happened to have two captive chimpanzees. This early exposure to these animals would prove crucial in triggering a long-lasting interest in primate emotions and cognition.

Inspired by the work of Dutch ethologist Niko Tinbergen, de Waal earned his doctorate in biology from Utrecht University in 1977, with a dissertation about agonistic interactions and relations among Java-monkeys. In 1981, he moved to the United States to take a position at the Wisconsin National Primate Research Center. Later, in 1991, he was offered a position as C. H. Candler Professor in the Psychology Department of Emory University, Atlanta (Georgia), where he remained until his passing.

De Waal's groundbreaking research

When de Waal began his investigations, in the 1970s, primate societies were understood as product of aggression and dominance. In De Waal words, “Animals were to be described as soul-less machines”. However, early in his career, he began questioning whether chimpanzees have inherited more from their ancestors than just the simple struggle for power. His observations revealed that after a fight, an individual would extend their hands to the other, offering hugs and kisses to reconcile. Could this mean that chimpanzees exhibit empathy, forgiveness, and consolation, much like us humans?

Like anyone who thinks outside the box, de Waal’s pioneering research on primate emotions and intelligence was not initially well-received by other researchers. At that time, ethologists were trained to refrain from making inferences about intentions or emotions in animals. Contending that animals show empathy or justice, the foundation of human morality, was not only heretical but could have even jeopardized de Waal’s career before it even began.

A major contribution of De Waal is to show that it is indeed possible to delve into the morality of animals through scientific inquiry.

Credibility in sciences comes from objective evidence rather than subjective interpretations. Yet gathering evidence about moral behaviors in animals is no straightforward task. How can one convincingly demonstrate that an animal exhibits a sense of justice, forgiveness, or consolation? A major contribution of De Waal is to show that it is indeed possible to delve into the morality of animals through scientific inquiry.

In one famous experiment, de Waal and his students trained captive capuchin monkeys to exchange tokens for cucumbers—a food they liked. Unsurprisingly, the monkeys performed this task proficiently. However, when an individual happened to observe another monkey receiving grapes instead (a food they liked even more), they immediately rejected the cucumber they were offered. This behavior seemed irrational, as one would assume that any food is better than none. The only plausible explanation lies in a sense of justice.

Throughout his career, de Waal studied a wide range of animals —including several primates, elephants and dolphins. Yet it was the Bonobo that left an especially lasting impression on him. Despite being closely related to chimpanzees, he soon realized that their behavior could not be more different. Unlike chimpanzees, which are quite aggressive toward others, bonobos proved to be highly peaceful. Through meticulous observations, De Waal discovered that bonobos not only exhibit greater tolerance towards strangers but also tend to resolve conflicts through affection rather than aggression. This marked a paradigm shift in our comprehension of animals, challenging the prevailing notion that their relationships revolve solely around status and dominance. Cooperation and empathy could be equally or even more crucial in primate societies.

Remembering de Waal only for his trailblazing research and remarkable discoveries would be an incomplete portrayal of his legacy. Equally noteworthy is his prolific and successful career as an author of books for the general public. With 16 books under his belt, translated into over 20 languages and boasting millions of copies sold worldwide, de Waal's impact reaches far beyond academic circles. In one of his most famous books, “Chimpanzee Politics”, de Waal explores the intricacies of power, alliances, and social interactions within chimpanzee societies. In “Mama’s Last Hug”, he reflects on primate emotions and discusses how studying them enlightens our understanding of ourselves as humans. His last book, “Are We Smart Enough to Know How Smart Animals Are?”, delves into animal intelligence, challenging assumptions about the uniqueness of human cognitive abilities.

The messages conveyed in these and other de Waal’s books have deeply penetrated our culture. If we now use concepts like “Machiavellian intelligence” or “alpha male” in everyday language, if we realize that animals have rights and must be treated with respect, and if we understand that leadership transcends mere imposition to embrace generosity, gratitude and justice, we largely owe it to his work.

De Waal’s groundbreaking contributions has enriched our understanding of animal emotions and intelligence, blurring the boundaries between us and the rest of animals. His legacy will always be remembered.

Obituary written by:

Daniel Sol