03 May 2024

Two obituaries of Frans de Waal (1948–2024). And why Frans de Waal hated vegans.

Andrew Whiten wrote an obituary about Frans de Waal in Nature [1] and Sarah Brosnan did so in Science [2]. Both use the same quote of the deceased primatologist: "I’ve brought apes a little closer to humans but I’ve also brought humans down a bit." In this blog I will add a few lesser-known facts about his life which are absent from the published obituaries and the reviews of his books.

Capuchin monkey fairness experiment

Sarah Brosnan joined de Waals lab as a graduate student in1998 and completed her PhD under his direction in 2004. The discovery that Capuchin monkeys reject unequal pay (video above) made her famous. Andrew Whiten is Emeritus Wardlaw Professor of Psychology in the School of Psychology and Neuroscience at the University of St Andrews, UK. The hilarious video fragment with two Capuchin monkeys went viral with 1,5 million hits. In the video one monkey gets a piece of cucumber and the second a grape (which is a higher-value food). The first monkey gets angry and throws his cucumber back to the researcher and protests loudly. This proves monkeys have a feeling for justice and don't like unequal treatment. This is a property previously thought to exist only in humans. Therefore: "I’ve brought apes a little closer to humans but I’ve also brought humans down a bit." The experiments were published in Nature [3,4].

Sarah Brosnan wrote in Science [2]:

"Frans de Waal, groundbreaking primatologist, died on 14 March. He was 75. De Waal spent his career, as both a scientist and an award-winning science writer, shrinking the distance between humans and animals. He demonstrated through careful observations and experiments that animals exhibit complex thoughts and behaviors that had long been considered the exclusive domain of humans." ...
"He went on to show that many primates cooperate, care about equity, show empathy and emotional contagion, help one another, " ...

“That’s how you can sum up my career: I’ve brought apes a little closer to humans, but I’ve also brought humans down a bit.”

Andrew Whiten wrote in Nature :

"de Waal’s research portfolio extended to diverse species, notably elephants, capuchin monkeys and bonobos (Pan paniscus), tackling typically human concepts such as morality, fairness and empathy." [1]

Indeed, Frans de Waal researched chimps, bonobos, monkeys and elephants [8]. De Waal and Sarah Brosnan [5], [6] also wrote about morality and empathy. 

In 2005 De Waal wrote 'Good Natured: The Origins of Right and Wrong in Humans and Other Animals' and in 2006 he was the editor of the book: 'Primates and Philosophers: How Morality Evolved' (in which Peter Singer is a contributor). In that volume de Waal - contrary to Singer - denies animal rights. In 2009 De Waal wrote The Age of Empathy: Nature's Lessons for a Kinder Society
In 2011, De Waal and colleagues went on to prove that chimpanzees are inherently altruistic as well [7].

In 2013 De Waal published a remarkable opinion piece Zijn vleeseters agressief? (Are meat-eaters aggressive?) in the Dutch Psychologie Magazine. He wrote that cultured meat is a good invention because no central nervous system is involved, so no animals suffer. However, at the same time he ridicules vegans like for example the American psychologist Melanie Joy, author of Why We Love Dogs, Eat Pigs, and Wear Cows [9]. It is unclear why De Waal attacks people (vegetarians and implicitly vegans) who support a better treatment of animals, are committed to banish factory farming and are phasing out or stopped eating meat altogether. Vegans do no hurt humans or animals. So, why attack them? Furthermore, De Waal strongly argues against the idea that meat-eaters are more aggressive than vegetarians [10].  

On August 20th 2017 Frans de Waal said on Dutch tv that the meat industry is bad, but he defended eating meat by an 'appeal to nature' (or naturalistic fallacy). This is not well-known, even in the Netherlands. The obituaries of Frans de Waal do not mention it.

Mama's last hug

In his book Mama's last hug. Animal Emotions and What They Teach Us About Ourselves  (2019) there is an important paragraph 'Meat and sentience' (in chapter 7 'Sentience: what animals feel') in which he reveals: 

"Even if I have no problem with meat-eating per se, there is a lot wrong with how we treat animals and how we raise, transport, and slaughter them."  "I have joined it [meatless diets] in my own imperfect and undogmatic fashion by banishing practically all mammalian meat from my family's kitchen." [12]. 

In 2022 de Waal published Different: Gender Through the Eyes of a Primatologist. He wrote about baboons: "They like meat but eat mostly plants." and about chimps: "Whenever chimps capture prey, male hunters share meat preferentially with swollen females."

On 20 April 2023 De Waal says again on Dutch tv that the way pigs are treated is bad [11], but did not say he stopped eating meat all together.



Frans de Waal is a clear example of a person with cognitive dissonance. Cognitive dissonance is the mental discomfort people feel when their beliefs and actions are contradictory, ultimately making them change either their beliefs or actions. Frans de Waal changes both his beliefs and his actions. He believes that the 'meat industry is bad' and that it is a moral imperative to phase out eating animals [13]. Then he realizes that his meat eating behavior is in conflict with his beliefs. He tried to solve this conflict in two ways: by believing that 'meat eating is natural' (and by implication vegetarianism is unnatural), and by changing his behavior: he 'banished practically all mammalian meat from his family's kitchen'. 

All dissonance solved? No. This is an incomplete solution because there is still some dissonance left. Science tells him that all animals with a central nervous system can feel pain. So what about chickens and fish? He knows that chickens are treated badly in the meat industry. Furthermore, a vegetarian diet still uses animal products from factory farming (milk, cheese, eggs). The solution would be veganism (change of behavior). He did not do that. In stead he chose to attack vegans and veganism. He believed that 'we are not meant to be vegan'. Also: vegans are dogmatic and I am not dogmatic. That's why he hated vegans. In this way he resolved his cognitive dissonance. His behavior seemed to be in harmony with his beliefs.

All dissonance solved? Not quite. Whether 'we are meant to be vegan' is irrelevant for the moral question. Animals suffer whether or not humans are meant to be vegan. And it is not relevant whether carnists are more aggressive than vegans or not. And it is also irrelevant for the moral question whether vegetarianism is difficult to maintain. Unfortunately, Frans de Waal did not live long enough to draw the logical conclusion from the fact that all creatures with a central nervous system can feel pain. It has not escaped our notice that Frans de Waal may not be the only person struggling with this kind of cognitive dissonance.


  1. Andrew Whiten (2024) Frans de Waal (1948–2024), primatologist who questioned the uniqueness of human minds. Nature 10 April 2024. Andrew Whiten is Emeritus Wardlaw Professor of Psychology in the School of Psychology and Neuroscience at the University of St Andrews, UK.
  2. Sarah F. Brosnan  (2024) Frans de Waal (1948–2024). Primatologist who brought animals and humans "a little closer". Science 25 Apr 2024. 
  3. Sarah F. Brosnan, Frans B. M. de Waal (2003) Monkeys reject unequal pay
    18 September 2003
  4. Sarah F. Brosnan, Frans B. M. de Waal (2004) Fair refusal by capuchin monkeys, 11 March 2004 
  5. A  Comparative  Perspective  on  the  Evolution of Moral Behavior
    Katie Hall and Sarah F. Brosnan (chapter in: The Evolution of Morality).
  6. Brosnan, as a student and colleague of de Waal, studied animals and wrote about morality, but did not openly argue against eating meat. Maybe de Waal's attitude influenced her.
  7. Frans de Waal, biologist who championed animal intelligence and emotion, dies at 75  National Geographic, March 21, 2024
  8. De Waal did not study cows, pigs and chickens. He discusses pigs in Mama's last hug. Cows, pigs and chickens are considered food and exempt from legal protection. It is legal to kill them. In the Netherlands it is illegal to kill your cat or dog. It should only be done by a veterinarian.
  9.  Her book Why We Love Dogs, Eat Pigs, and Wear Cows and especially the concept carnism  is an eye-opener. Required reading. Melanie Joy showed that by naming eating meat carnism, it becomes clear that is an ideology. Carnism is an ideology that is never questioned. Carnism requires justification just as any moral choice.
  10. It seems to me completely irrelevant to the moral issue of killing animals for meat. So, why bring it up?
  11. My blog Zo kijkt Frans de Waal naar mens en dier. VPRO Tegenlicht. Ik snap het niet  20 April 2023.
  12. 'meat eating per se' is an abstract theoretical situation. In practice human meat eaters completely depend on the meat industry. De Waal first shows irrelevant evidence that vegetarianism is difficult to maintain (16/77 of chapter 7 eBook), than says "I admire the effort" and than describes his own effort as 'undogmatic'. This implies all strict vegetarians are dogmatic, and he himself has superior ways of thinking and doing things. This is a way to turn a personal failure to ban all meat in to a success. He hopes the meat industry will change in stead becoming a vegan.
  13. "I see the pursuit of such goals as a moral imperative, but it will be best accomplished if we honestly face where we come from rather than spinning the fairy tale, often heard these days, that we are meant to be vegan. We are not." (chapter 7, 17/77 eBook Mama's ast hug). Whether some vegans are supposedly claim silly things, is not relevant for his 'moral imperative.' Again, pointlessly attacking vegetarians and vegans!