NPR – Transcript of Interview with Frans de Waal

By: Terry Gross

March 19, 2019

A chimpanzee hugs her newborn at Burgers’ Zoo in Arnhem, Netherlands, in 2010. Over the course of his long career, primatologist Frans de Waal has become convinced that primates and other animals express emotions similar to human emotions. AFP/Getty Images

This is FRESH AIR. I’m Terry Gross. The animals genetically closest to humans, chimps and bonobos, also express a lot of the same emotions we do, according to my guest Frans de Waal. He’s been accused of anthropomorphism – attributing the characteristics of humans to animals – but his research has convinced a lot of skeptics that animals do express emotions similar to ours. He’s been studying primate behavior and emotions for 40 years. His primate research is observational and noninvasive.

He began his research in the Netherlands, where he was born and grew up. He’s now the director of the Living Links Center at the Yerkes National Primate Research Center near Atlanta, where his office window looks out into the colony of chimps whose behavior he studies. He’s also a professor at Emory University and a longtime board member of Chimp Haven in Louisiana, the world’s largest facility for chimps who are retired from being used for lab research. His new book is called “Mama’s Last Hug: Animal Emotions And What They Tell Us About Ourselves.”

Frans de Waal, welcome to FRESH AIR. You keep offering evidence that primates have emotions like humans have emotions, and that might seem obvious to many people now, but it wasn’t obvious when you were starting out studying primates. What were you told, when you started out, about primate emotions?

FRANS DE WAAL: We were told not to talk about them because they were considered by many scientists as inner states, and you only were allowed to talk about outer states. So you talk about the things that you can see, and emotions, they feel, are assumptions about feelings and stuff like that, and they – and actually, thoughts also. So thoughts and feelings, the mental processes, basically, were off-limits, which is sort of curious because Darwin already talked about the emotions in man and animals. And so Darwin was allowed to talk about it, and then we got this dark period in which we were told – as a student, I was told not to speak about these things.

GROSS: So the most poignant example of primate emotions that I’ve ever seen is the video from which your book takes its title, “Mama’s Last Hug,” and this is basically a deathbed visit to a 50-something chimp named Mama who was the alpha female of the chimp colony at the Burgers’ Zoo, where primates were being studied. And the visitor was your mentor, Jan van Hooff, who was 80 at the time of this visit. Would you describe what happens in this visit?

DE WAAL: Well, what happened is that Mama, who was the alpha female and absolutely central figure of the whole colony there, she was dying, and Jan van Hooff, my professor, he decided to enter her night cage, which we normally never do. You never go in with an adult chimpanzee because they’re far too dangerous, and they’re volatile, and so on. But since she was dying, and since he had known her just like I have known her, for 40 years, so was on very good terms with her, but had always visited her with bars in between, he decided to go in.

And what’s interesting is that, apart from the response that she had – she had a big grin on her face, and she embraced him and patted him on the back, and things like that – was that she was reassuring him. She must have sensed – and this was typically Mama because she was a very sort of calming figure in the colony – she must have sensed that Jan van Hooff was nervous, and that it was extremely unusual situation, and so she calmed him down.

And the thing that struck me is not so much that people were moved by the video, because it was first shown on national TV in Holland and then later on the Internet. That people were moved was completely understandable. I was very moved by the whole thing. But that people were surprised how human-like the expression of Mama was and how human-like her gestures were. And that is something that struck me, is I thought, well, everyone knows that chimps are our closest relative, so why wouldn’t the way they express their emotions be extremely similar to ours? But people were surprised by that.

GROSS: You know, it’s really such a beautiful video because he’s petting her, and she’s kind of petting him. She’s stroking him. And when he walks in, she has this, like – you know, she’s just been lying there expressionless, with her eyes open. They look like the eyes of an animal that’s dying. But when he walks in, like, she – I’ve never seen, like, a chimp smile like that.


GROSS: I mean, like, her whole face changes, and her whole mouth just changes. So it really is beautiful. What was the nature of your relationship with Mama?

DE WAAL: Oh, I was just as close. I didn’t live as close as Jan, but – because I live in the U.S. But each time I would show my face at the zoo, even if I was among hundreds of visitors, she would pick me out, and she would come over to greet me from across the moat because they live on an island most of the time. So I had a very close relationship with her. And she was actually not just a diplomat in her own group because she – it’s a very big chimp colony of with 25 individuals and a lot of power struggles and stuff like that. But also she was a diplomat to the outside, to us humans who took care of them at the zoo. And so she maintained relationships with lots of people.

GROSS: And you write that you had grooming sessions with her. Would you describe what happens in a grooming session between a human like you and a chimp like Mama?

DE WAAL: Oh, they – you know, they love to groom the – actually, you should be careful. If you have a little injury on your hands or your arm, they try to open it because they – that’s how they clean injuries on each other (laughter). And so they – and she likes to groom very small details, like the whimpers (ph) on your eyes and things like that. And so she would love to groom me, and I would groom her a little and talk to each other and stuff like that, so.

GROSS: Tell me more about what the grooming means. Like, what are you doing to her, and what is she doing to you?

DE WAAL: Grooming is mainly a social activity, especially for animals at zoos. So in the wild, of course, there are ectoparasites, and there are ticks and things like that that need to be removed, and so grooming has a major function, is a very important behavior. But also in the wild, I would say that the grooming – they do more grooming than is strictly needed for hygiene because it’s a calming activity, both for the one who performs it and the one who receives it. And we have still leftover of that, when you go to the barber or the hair stylist, and that’s a lot of grooming there.

But in the chimps, it’s very much a bonding ritual, and so it’s used after fights to calm each other down. It’s used to negotiate. Like, you may groom the alpha male to get certain favors from the – so grooming is basically a service that you exchange. It’s one of the many services that chimps exchange because they have a lot of, let’s say, a service economy going on among themselves.

GROSS: So Mama had a roommate. I guess this was at night that they would go into cages? Like, describe that situation. Is that what it was?

DE WAAL: Mama had a roommate, which her name was Kaif (ph). And not only would they sleep together in the same cage at night, but in the daytime, when they were in the colony with the other 25 chimps, they would also very often be together because Kaif was basically the right-hand woman for Mama. And so they would – they had a coalition, as we usually call it, and a very politically important one because the males knew that if they had a fight with Mama, they had a fight with Kaif at the same time. So it was obvious that the males knew that they had – were always dealing with two females there.

And so when I would approach her night cage and try to have an interaction with Mama, Kaif would be there. But in the beginning, Kaif would always try to dominate me and take advantage of the fact that Mama was sitting there, her big supporter, and she would try to hit at me and things like that. Chimps always try to get the upper hand. Mama didn’t do that with me. But her friend tried to do that.

And that whole attitude of Kaif changed 100 percent after I helped Kaif raise children because Kaif had trouble with lactation. She didn’t have enough milk production. And so she lost a few infants, and this was a terribly depressing time for her, and she would be crying and not eating, and she was extremely depressed by losing her infants. And at some point, I decided, since we had an adopt – a baby up for adoption, a baby chimp up for adoption, I decided to teach her how to bottle-feed a baby. And so from that moment on, she adopted an infant that she raised on the bottle, and then she raised her own offspring. In the years after, she raised her own offspring also on the bottle.

GROSS: How did you teach Kaif how to bottle-feed her baby and the adopted baby that you gave her? And the adopted baby was from a female chimp who was deaf and had trouble raising her baby.

DE WAAL: Yeah, so that female was deaf, and she had lost also a couple of babies because of her deafness and not responding well to the baby. And so we decided we were not going to have her have babies anymore, and that’s why we handed it over to Kaif and taught her how to bottle-feed. And the way we did that is that I kept the baby for six weeks, I believe, together with the caretaker, female caretaker. We together held the baby. And so for six weeks, we held it on our site, and we taught Kaif how to hold a bottle and feed it to the baby, and that the baby would be suckling and all of that.

And then after six weeks, we gave it to her. We put it in the straw of her cage, and she would find it there. And the funny thing was that, in the beginning, she didn’t want to take it, and that is, I think, because she considered it our baby, which is obvious because we had had it for six weeks. And in chimps, it’s not very well regarded to take the baby of somebody else, and so she was extremely reluctant to even approach it. And she kept looking at us, and we kept saying, well, you go. Go ahead, and stuff like that. And at some point, she approached the baby. She took it, and she never left it from that moment on.

So she adopted that baby chimp. And since that time – and I described it in my text as gratitude. Just – I saw it as a sign of gratitude. She was extremely friendly with me. I was basically a family member. She never, ever struck out at me again after that time. And she was very much in favor always when I came and always very sad if I left because she – I was – had become part of her family, I think.

GROSS: So one of the things you learned about this bottle-feeding exchange was that chimps are capable of something you would describe as gratitude. But what else did you learn from teaching an adult female how to bottle-feed a baby?

DE WAAL: Well, one of the things we saw was that she was very adept with the bottle because she did a bunch of things that we never had taught her, like watching when the bottle was getting empty or pulling it out if the baby was almost choking on it and – or needed to burp. And she did a whole bunch of things that we had never taught her. And so she understood how the thing worked. And also, she bonded very strongly with that infant, even though she knew it came from us, which, basically, became her daughter and is now – is still in the colony and still – and she has offspring of her own also.

GROSS: And we should explain the colony that Mama and Kaif (ph) were part of is a colony of chimps in a zoo in Holland, where you’ve studied them. And…

DE WAAL: Yeah. I’m from…

GROSS: It’s a colony for study.

DE WAAL: Well, I’m from the Netherlands. The colony was founded in a time that all chimps were kept in small cages in small groups because the zoos in the world had decided that chimps were to be kept a bit like gorillas – like one male and three females or something like that – even though in the wild, of course, chimps live in large groups of, sometimes, 12 males, sometimes even 20 males – adult males.

And so when this colony was set up at the time, there was a lot of resistance of people, a lot of skepticism. People said, well, this is never going to work. If you have so many males together, they’re going to fight. And they’re going to kill each other. And so there was a lot of problems with that.

But, actually, that colony in Burgers’ Zoo is an example now for many zoo colonies in the world. And it has been the most successful breeding colony in the world, I think. So it was a great success. And I watched them mainly to study aggressive behavior because at the time that I was a student, that was the popular topic that everyone should study is, where does aggression come from? And what is the aggressive instinct?

And in the meantime of studying their mind, I got interested in, actually, the opposite of aggression. I got interested in reconciliation. How did chimps make up after fights? That – I found that more interesting than all the aggression that I saw. And so I got interested in how they kiss and embrace after a fight, how they groom each other and how they maintain the peace, basically.

GROSS: Give us an example of something you witnessed showing how chimps reconcile.

DE WAAL: Yeah. I think one of the most striking observations was the first one I made when I didn’t even expect the phenomenon. I didn’t know about it because no one talked about these things. And so at some point, I saw a big fight in the colony between two individuals. And I had recorded all of this. We had the first video recorders of the time, which was pretty amazing technology at the time. And so I had recorded it.

And a couple of hours later, I saw a big commotion in the group and two individuals hugging each other and all the rest of the chimpanzees hooting and yelling and gathering around them. And I did not understand what was going on. I had no clue. And in the evening, I biked back to my home. We do everything on bike in Holland. So I biked back to my home. And thinking about the incident, I thought, well, that’s actually the same two individuals who had the fight.

So – and that’s where the word reconciliation popped in my mind. Like, you know, I’m from a very big family. So I’m very used to the mechanism. And so that’s why I thought, it could be a reconciliation. And from that moment on, I started looking for it. I started – each time there was a fight in the colony, I thought, well, what are they going to do afterwards? And I noticed that half the time, they come together. And they kiss. And they embrace. And they groom each other.

And I got really interested in that phenomenon. And I decided to make a study out of that, in the sense that I decided the rest of my career I was going to devote to that kind of mechanisms – the sort of mechanisms that chimps or bonobos or other primates use to maintain the peace, to have a cooperative relationship. Do they have empathy for each other? That sort of phenomena I really got interested in.

GROSS: Let me reintroduce you here. If you’re just joining us, my guest is Frans de Waal. He studies animal behavior. He’s the director of the Living Links Center at Yerkes Primate Research Center, which is in and near Atlanta. They have separate facilities. And he also teaches at Emory University. His new book is called “Mama’s Last Hug: Animal Emotions And What They Tell Us About Ourselves.” We’ll be right back. This is FRESH AIR.


GROSS: This is FRESH AIR. And if you’re just joining us, my guest is Frans de Waal, who’s well-known for his research into primate behavior. He has a new book called “Mama’s Last Hug: Animal Emotions And What They Tell Us About Ourselves.”

So in studying animal emotions, you’ve studied a lot how primates reconcile after fights. But you also study things that are disturbing. You like – you don’t back away when you see something that’s disturbing. And you now think that chimps are capable of murder. And you don’t use the word murder without careful consideration. There was an incident in 1980, which you came to think of as a murder. And I want you to explain what happened and why you thought of it in terms of murder.

DE WAAL: Oh, what happened – I was studying the power struggles among the adult males in the colony. And there’s just occasional fights. But they’re not too bad, usually. And – but in this case, it completely went out of control because the males were at night – in their night cages. And we had tried to separate them the day before. We had done our best to separate them at night because we were worried about the tensions between them. But they didn’t want to be separated. They kept clinging to each other. And each time we tried to lower the door, they shuffled in it together. And so at the end of the evening – it was a long evening. We gave up, and we decided to let them sleep together and gave them a whole bunch of night cages so that they could move around. But in that night, one of the males – the leading male – he got basically killed. Well – and the next morning, I found him bleeding and near death, and he died later in the day. And so what happens is that the two other males had ganged up on him, and they had barely scratches. So they had very well coordinated.

And at the time, I must say I was disturbed because I thought maybe this is an effect of captivity, and this would normally never have happened. But now we know, actually – and I described many cases – we know many of them in the wild, as well. So in the wild, chimpanzees – they do kill between groups. So males who are strangers to each other – that’s a fairly common occurrence. But also, on occasion – the way it happened at the Arnhem colony – on occasion, they do it within the group. And so these are political struggles where they really go to the extreme. And the unfortunate thing of that whole incident is that if the females had been there, the females would’ve stopped this thing. I’m sure. The females do…

GROSS: How would they have stopped it?

DE WAAL: Well, the females would’ve jumped in and beaten them apart. So if you have – in a captive colony, the females are more powerful, actually, than in the wild because in the wild, the females are dispersed over the forest, usually. But in a colony on an island, like in Arnhem, you have 12 females. And they band together, and they are extremely coordinated. And if mama – the alpha female – decides that that fight is not worth it, she’s going to jump in and kick them apart.

GROSS: So you just grab the two chimps murdering the alpha chimp. But it was a very brutal murder, and it sounded like there was almost, like, sadism involved with it. So – maybe sadism isn’t the right word, but I want you to describe more about how brutal this was.

DE WAAL: This is very similar to what – in the wild, I have also seen – is that it seems intentional. And the descriptions of chimps in the wild are, very often when they kill each other, that multiple males gang together. And it seems that intentionally bring down the other – and in our case, these two males – they had mutilated that one male terribly, and they had even castrated him. And they had caused so many injuries that in the end, he died of blood loss. We couldn’t replace that. And so it was absolutely brutal, yeah.

GROSS: My guest is Frans de Waal. His new book is called “Mama’s Last Hug: Animal Emotions And What They Tell Us About Ourselves.” After we take a short break, he’ll tell us how female bonobos assert and maintain power. And also, Maureen Corrigan will review a new book about the friendship and then the falling out between Langston Hughes and Zora Neale Hurston. I’m Terry Gross, and this is FRESH AIR.


GROSS: This is FRESH AIR. I’m Terry Gross. Let’s get back to my interview with Frans de Waal. He’s been studying primate behavior and emotions for 40 years. He began his research in the Netherlands where he was born and grew up. He’s now the director of the Living Links Center at Yerkes National Primate Research Center near Atlanta and is a professor at Emory University. He’s also a longtime board member of Chimp Haven in Louisiana, which is the world’s largest facility for chimps who are retired from being used for lab research. His new book is called “Mama’s Last Hug: Animal Emotions And What They Tell Us About Ourselves.”

You popularized the term alpha male when using it to describe primate behavior. And what did you mean when you started using it?

DE WAAL: Well, alpha male in my field just means the top male. You have the top male and the top female. You have only one of them. You cannot have two alpha males in a group of chimps or two alpha females. So it means the top individual. And the term comes out of Wolfe Research. The Wolfe researchers – they use that term, also, just for the top male or the top female.

GROSS: And you say sharing is a very important part of getting and maintaining alpha male power.

DE WAAL: Yeah, the alpha male has many duties, I think, also. And an alpha male keeps the peace in the group. A good alpha male breaks up fights and defends the underdog, not – usually not the winners, but the losers. And the alpha male also is the consoler-in-chief – goes to individuals after a fight to console the ones who have lost and sit with them and grooms them and hold them and things like that. And so the consoler-in-chief role is extremely important. And an alpha male who is good at that – he is also usually kept in power for longer.

So in a chimpanzee society, you’ll always have challengers to the top male. And it’s almost as if the group is waiting. If the male is a bully that they don’t like, they’re almost waiting for that challenger, and they’re going to put their weight behind him. And if it’s a good alpha male that who keeps order and is protective and is not abusive, then they try to keep that male in power.

GROSS: Let’s talk about female power in the primate world. You’ve told us a little bit about female chimps and – through the story of Mama. But bonobos in the wild – the alpha females are especially powerful. And you say it’s usually a female that’s in charge of the bonobo colony. How do females – female bonobos get and assert their power?

DE WAAL: Yeah, so the bonobo is interesting that – we have two close relatives, the chimpanzee and the bonobo. They’re equally close to us, genetically exactly equally close. And so they’re equally relevant in my opinion even though many anthropologists have prefer to chimpanzee. The chimpanzee is male-dominated, quite aggressive, has war going on between groups basically because they kill between groups. And the anthropologists have flocked to the chimpanzee and have ignored the bonobo because the bonobo is very sexy and peaceful and female-dominated, and they just don’t know what to do with that.

I don’t know a single colony of bonobos in captivity that is not led by a female. And in the wild, we now know that most of the time also at the top of the hierarchy is females more than males. So the bonobos are a very female-dominated society. If you ask, how do these females get to the top, that’s an interesting problem. I think in female chimps, like with Mama, or in female bonobos, age and personality are the main factors. And so there’s actually very little open competition and politics going on the way it is among the males. That is, if you wait long enough and you get old enough and you have a strong personality, you can be the alpha.

In both bonobos and chimps, I very rarely see a sort of middle-age female dominating these older females. If you have a group, let’s say, with a few 25-year-old females and a few 40-year-old females – and the 40-year-olds really are physically not as strong as the 25-year-olds, I can tell you – it’s going to be the 40-year-old females who are at the top. That’s a very different situation from the males. In the males, if you get too old, you get weaker, and you’re gonna be kicked out of the top position.

GROSS: I don’t know if, like, female – if certain female chimps and certain female bonobos are perceived as being, like, more sexually attractive than others, but is there any correlation between, like, sex and power or reproductive years and power?

DE WAAL: In humans and in all species, this is fairly typical – is that a male – and this is universal – a male can increase his reproductive success, which is the driver of evolution – a male can increase it by mating with lots of partners. So a male chimpanzee who mates with 20 females – he can in principle have 20 babies. A female chimpanzee who mates with 20 males doesn’t make any difference. He still gets one baby. And that’s why the rules for males and females in reproduction are totally different.

And the power structure reflects that – is that males – often they try to reach the top position, and that gives them mating privileges. For the females, I don’t think that’s the issue. Mating privileges are not the issue. For female primates in general, what is the issue is food. In order to raise offsprings and to be successful at that, you need to gather enough food. And so there is competition among females. And in many primates, we find very intense competition among females, but it’s usually about food. It’s not about sex.

GROSS: So another thing about primates – and I think this is true of all primates. You can correct me on this. But, like, they can mate, like, and the female can have a child, but they’re not – they don’t form couple relationships. You know, the father doesn’t become – the father and the mother don’t become a pair. So does the father take no responsibility for the baby?

DE WAAL: I consider that actually the biggest difference between us humans and the two apes who are closest to us, chimps and bonobos. I know people always like to emphasize our intellectual capacities and language and stuff like that. But actually, the fact that we form families – stable families with male, female, offspring – is drastically different from what we see in the other apes.

So in some of the primates, there are males involved in offspring care. But in our closest relatives, that’s not the rule. And so a chimp male or a bonobo male – they do extremely little. And that’s also why it all comes down to the female. And that’s why the females have these very long interbirth intervals, and that means that a female bonobo or a female chimp – they get a baby about every six years. They cannot do more because at some point, they shift their baby from the belly to the back. And at that point, there’s a place open at the belly, but they have to travel through the forest, through the trees with these offspring clinging to them. And so they cannot have two offspring. It’s just too many for them.

And so that’s why they have a long interbirth interval. And we have a shortened one. We have – maybe we can have one after two years, and that’s all because males are involved in offspring care. And so we have cooperative breeding. So females help each other. That’s also very important. But on top of that, we have males being involved. And the human male actually is more inclined and more motivated and has hormonal changes when he has an offspring. So the human male is sort of predestined to be at least a little bit or sometimes a lot being involved in offspring care.

GROSS: OK, so we’re going to take a short break, and then we’ll talk some more. If you’re just joining us, my guest is Frans de Waal, who studies animal behavior in primates. And he’s especially interested in emotions in animal behavior, and that’s what his new book is about. It’s called “Mama’s Last Hug: Animal Emotions And What They Tell Us About Ourselves.” We’ll be right back after this break. This is FRESH AIR.


GROSS: This is FRESH AIR. And if you’re just joining us, my guest is Frans de Waal, who studies animal behavior. He’s the director of the Living Links Center at Yerkes Primate Research Center, which is located in and around Atlanta. He’s a professor at Emory University and author of several books, including the new one “Mama’s Last Hug: Animal Emotions And What They Tell Us About Ourselves.”

So here’s an interesting experiment that you conducted that I want you to tell us about, and it involves two capuchins, small primates. And it involves grapes and cucumbers. Tell us about the experiment and what you were trying to…

DE WAAL: Well, I’ve…

GROSS: …Show, yeah.

DE WAAL: I’ve always had a capuchin monkey colony. And the capuchin monkeys – they lived in groups. And then sometimes we would take two of them out and do – bring them in a test chamber and test them out on food sharing or cooperation or whatever it was. And we always noticed during these experiments that the monkeys were very much watching what the other one was getting. So instead of just caring about their own rewards, which you would expect them to do – like, how much did work, and what do I get for it – they were watching what the neighbor was getting.

And so with Sarah Brosnan, I decided we’re going to test this out. We’re going to compare a very simple task. We give them different rewards for the same task. And so the task was very simple. We throw a little rock in there, in the test chamber, and they have to hand it back to us. And if you give both monkeys pieces of cucumber, they’re perfectly fine, and they will do it 25 times in a row without any problems. If you give both of them grapes – and grapes are 10 times better than cucumber – they also perform 25 times without problems.

The trouble starts when you feed one monkey grapes and the other one cucumber. Now, the one who is short-changed because cucumber is not as good then starts to refuse and actually becomes agitated and may throw the cucumber out or may at least stop performing and sit in the corner and not give anything about the test anymore, which is very strange because the food is normally good. And any time you give a piece of cucumber to one of these monkeys, they will eat it. But under these circumstances, they don’t. So they get sort of pissed off at the whole situation.

And so I got interested in that, and it’s an inequity response. It has to do with fairness. We started testing it out then later in chimpanzees, which have a sense of fairness that gets much closer to ours. But in the monkeys, already it works that way. And people have tested actually also dogs that way. They can perform a very simple task, and they get unequally rewarded. And dogs – you can do that experiment at home basically if you have two dogs. Dogs are sensitive to this, too.

GROSS: Yeah. And I should say with the capuchin monkeys there’s a video of this that you’ve used in your talks. And I’ve seen it, and, like, the capuchin monkey that’s getting short-changed and is getting the cucumber while the monkey in the cell next to him is getting the grapes – the cucumber guy starts getting, like, so upset. He’s, like, basically throwing the cucumber at the person who’s feeding it to him and then, like, rattling the cage and, like, pounding (laughter) the wall of the cage. I mean, he’s really angry.

And so, like, you’ve compared this to, like, political inequity and why people who know that other people are getting more and who therefore feel like they’re being treated unfairly – this sense of, like, you have more anger when you see injustice than you – like, if you don’t have something and you just don’t have it, it’s not as bad as not having something and realizing that other people have it and there’s some kind of inequity in the system where others are getting…

DE WAAL: Yeah.

GROSS: …Things that you’re not.

DE WAAL: Yeah. So it’s essentially an envy response. If you’re talking about emotions, the emotion behind it is envy or jealousy by the monkey who gets less than the other. And so that’s a very early response, and I think what we do in the human sense of fairness is we try to equalize outcomes in order to avoid these envy responses which are negative and destructive.

And so when you test chimpanzees who are much more like us – we did an experiment with chimpanzees and children actually, and the children and the chimps had the same responses. In chimpanzees, they try to equalize the outcome. So if you give a grape and cucumber to two chimpanzees, the one who gets the grape may refuse the grape until the other one also gets a grape. And so they try to equalize outcomes, which is very well-known of small human societies – is that they are very egalitarian and they try to – they have a very strong sense of fairness because unfairness undermines the society.

And that’s of course the problem that we face in our current societies which are largely anonymous and are so huge that people can get away with these inequities and people can get away by being the 1 percent grape eaters, so to speak. So people get away with these things, and it’s undermining the fabric of this society. So inequity is, in my opinion, not good for societies. And even chimpanzees know that, and they will try to share equally just as small-scale human societies do.

GROSS: Students who study animal behavior were always warned about anthropomorphism, which is when you attribute human characteristics to animals, like, oh, he’s so happy, or, look; he’s so sad. But you say that equally or perhaps even more dangerous is anthropodenialism. So compare the two for us, anthropomorphism and anthropodenialism.

DE WAAL: So anthropomorphism is a term often slung at us when we propose that your dog is jealous or that chimpanzees may be attached to each other or when you use human-like terminology – or they reconcile after fights. I was told actually for reconciliation to use post-conflict mouth-to-mouth contact because they kiss each other after fights. So they didn’t want me to use the word reconciliation because it sounds too human-like.

And I think for species that are close to us like the primates, anthropomorphism is really not a big problem because we are primates, and so we should use the same terminology. We don’t call the hands of a chimpanzee a front paw. No, we call it a hand because it is the same form, the same structure, the same bones as our hand. And so we should use the same terminology for structures that are similar but also for behaviors that are similar. And if you – let’s say you tickle a chimpanzee and they produce laughing sounds, like (imitating chimpanzee)-type laughing sounds, you have to call it laughing. It is laughing. It is not vocalized panting as people would want me to say.

So I think anthropomorphism is not such a big deal with species that are close to us, and that’s why I invented the word anthropodenial, which is the opposite – is that you deny that there are connections between humans and other species. And actually, entire areas in the university like philosophy, anthropology, parts of psychology – they are in anthropodenial. They live in a way – they think that the human mind and the human spirit are so totally different. We cannot compare them with what a monkey or a dolphin or which other animal is doing. And so they are denying that connection, which, I think, is detrimental and is, actually, much more dangerous, in my opinion, because anthropodenial has a lot of negative side effects in my mind. It’s much more dangerous than anthropomorphism.

GROSS: What are some of the other side effects?

DE WAAL: Well, one of them is we live, at the moment, in a time where we are destroying the planet. We humans are an ecological disaster. And entire species and large numbers of animals are disappearing. Forests is disappearing. The globe is warming.

And that is all a result, I think, of our attitudes that we can do whatever we want with nature because we are not really part of nature. We are sort of outside nature. And since we are outside, we can do whatever we want. And then I think that attitude is also reflected in how we look at other animals. And I think it’s a very dangerous attitude not to think that we are part of it. And we have to act responsibly within that framework.

GROSS: So your new book is all about, you know, primates – chimps, bonobos, capuchin monkeys – and how they express emotion. When you started doing this work, it was very controversial. Like, do primates really express emotion? And that’s been controversial, I think, in a lot of animal research. Do you think that we should not be debating anymore whether animals have emotions? We should just accept that they do.

DE WAAL: Well, I even take a more radical position, of course, in the book is that, I think, we have no uniquely human emotions. There are no emotions that we have that you don’t find one way or another. There may be variations that we have or different circumstances in which we feel these emotions. But I think all human emotions can be found in other species.

And we live at the moment in psychology with – the most popular theory in psychology is that there are only six basic emotions. There are six emotions that we – like anger and fear – that we humans express in the face and that we recognize in the face all over the world and is expressed the same way all over the world. There’s six basic emotions. And all the other emotions are secondary, meaning that they are a creation of our culture and ourselves and are not found, necessarily, in other species.

And I disagree strongly with that. For example, the secondary emotions include something like love and attachment. Now, love and attachment we find in so many species. We know, actually, the dopamine system that’s behind it. We know the oxytocin that’s behind it. And so why is love and attachment not a basic emotion? So I think there’s many emotions that don’t have a face – that don’t have a specific face that is – that are nevertheless found in lots of other species.

And I am now at the point that I think emotions are more like organs. I don’t have a single organ in my body that you don’t find in a rat body. We have livers and kidneys and hearts and brains and lungs. And all my organs are present in a rat’s body in the same way, I think, all my emotions are probably present in a rat.

GROSS: Frans de Waal, thank you so much for talking with us.

DE WAAL: You’re welcome.

GROSS: Frans de Waal is the author of the new book “Mama’s Last Hug: Animal Emotions And What They Tell Us About Ourselves.” After we take a short break, Maureen Corrigan will review a new book about the friendship between Zora Neale Hurston and Langston Hughes and their eventual falling-out. This is FRESH AIR.