On paper, the event seemed like it might be a total disaster: an Italian feminist film icon and a Dutch primatologist chime in on our embittered Gender Debate with an interdisciplinary conversation about ape sexuality. Cancellations seemed imminent. Culture warriors were expected in the crowd. Instead, when Isabella Rossellini and Dr. Frans de Waal took the stage this past May, the opposite occurred. Something quite rare: a curious, open-minded scientific conversation about the biological origin of transness and gender, the kind that has the potential to actually change people’s minds.

Ape societies, de Waal posited in his introductory presentation, have gender constructs much like our own. Adult apes pass down cultural habits to their young. Most chimpanzee girls imitate their mother’s nursing and eating habits, and most boys pick up these attitudes from random males. But not all apes act in accordance with their birth sex—such as de Waal’s chimpanzee friend Donna, the secret star of his presentation. Donna grew up preferring male company to female company—she loved to roughhouse with the boys—and in time developed a masculine character and physique. “I cannot ask Donna her identity,” de Waal concluded, “but I would say she was probably trans.”

De Waal estimates that between 5% and 10% of apes exhibit this kind of gender nonconforming behavior. What’s more, “unlike in human society, the apes are fully accepting of this diversity and such distinctions don’t cause any problems.” This may be worth noting the next time someone argues that trans identity seems like a recent, ideological invention—an essential subcurrent of the present hysteria.

Ester Segretto, 2023.Courtesy of the photographer

De Waal had a larger point to make about his field of study. Biology, he said, does not account for the traditional gender roles in our society. If it seemed so in the past, this was because a now-extinct generation of male primatologists and anthropologists overlooked all evidence to the contrary. Faced with two genetic relatives, equally close to the human species—the violent, patriarchal chimpanzees and the peaceful, bisexual bonobos—they focused almost exclusively on the chimps. And this guided and supported influential theories about who we are as a species. Many of the old guard’s deductions would be proven wrong, as more women worked their way into the field. Ape species that were long thought to be patriarchal—like baboons, or, the better angels of our nature, the bonobos—turned out to be entirely female-led.

Curious about the implications of this research, Isabella Rossellini (an animal behaviorist and farm owner, as well as an icon of the silver screen) took to the stage, armed with a stack of trenchant questions.

Why did you have the urge to write a book about gender relations in ape societies?

Every time I talk about animal emotions or intelligence, and mention the differences between males and females, people often zoom in on that question. They want to know more about it because many of them are skeptical about the cultural construction of gender in our society. It was not my intention to write about gender diversity—my initial impulse was to write about sex differences in primates and humans—but I found it to be a fascinating and underestimated topic.

You give the example of Donna, the ape who doesn’t conform to traditional gender roles. Do you have other examples? Have you seen males that are not dominant, that don't want to fight?

Yes, actually, in Arnhem Zoo, which I visited recently, the largest male—who you would think should be the alpha—was not interested in the games that the males played and completely stayed out of them. That happens actually quite often, that males don't want to be involved in these scuffles, which can be very stressful.

Do they get the girls? Do the females prefer males that are dominant?

The males who stay out of these political games are not the most popular among the females because they're also not very protective of them.

Primatologist Sarah Hardy has written about the strategies of female chimps. Apparently, the more promiscuous they are, the better chance they have of evading infanticide. Male chimpanzees sometimes kill babies if they have no relation to the mother, so the mother maintains relations with the males to spare her child. Could you explain that to me?

The thinking of Sarah Hardy and others is that females have as much sex as they do with males because the males may be following a rule such as, “be nice to the females and the young that you had recent sex with,” to exempt their own offspring from aggressive activities. Generally, female chimps have far more sex than is purely necessary for pregnancy. Particularly bonobos, but chimps too. It’s been estimated that a wild female chimp will have maybe six or seven children and copulate around six thousand times in her life.

Chimpanzees and bonobos behave very differently. Can you remind us of those differences and why they’re significant?

We have these two equally close relatives, chimps and bonobos. And of course, anthropologists always compare us to chimps. They like chimps because they’re violent and male dominated and territorial, which fits the story of human evolution that’s predicated on wiping out others and conquering the world. The bonobo doesn't fit that mold because it is peaceful and sexy and female dominated—too peaceful for the tastes of old-fashioned anthropologists. It has been marginalized as a result.

I find it fascinating that our two closest relatives are so different. There was a recent study of all the lethal aggression in chimps and bonobos in the field. Of 152 cases, 151 were committed by chimpanzees. In the one other case, the bonobo was merely a suspect. We primatologists have focused on the chimpanzee, but the bonobo is equally relevant and gives us totally different information.

Why are these two species so different?

We don't know exactly why. There are some theories about it having to do with food supply and the absence of gorillas in the bonobo habitat. Chimpanzees live with gorillas; bonobos do not.

In fact, bonobos were only declared a separate species relatively recently. They were mixed in zoos before, which must have been quite painful for them. You write so touchingly about these apes. One story comes to mind particularly: the chimp who lost a baby. You brought her an orphan, but had to teach her how to nurse with the bottle. Can you tell us that story?

Yeah, that was a female named Kyve who had lost three babies because she didn’t have enough milk for them. Each time, she went into a deep depression. It was horrible to see; she would be sitting in a corner, crying for days. At some point we wanted to sterilize her, but then a baby became available. I took the baby chimp and I demonstrated in front of Kyve how to bottle feed her for six weeks. I did that every day, and then after that period I gave her the baby. Among chimps there’s a sort of rule around not taking other’s children, so she didn’t want to adopt it at first. She didn’t want to take my baby away. We had to convince her to pick it up, and when she did she became a very good mother and went on to raise her own future offspring on the bottle. She was eternally grateful to me. I didn't have a particularly close relationship with her before, but after that she would run over to me and not let me go every time I visited.

Esther Segretto, 2023. Courtesy of the photographer

The way you talk about chimpanzees is very modern, even the way you describe her being “happy” to see you. Historically, scientists have wanted to be detached, and have given animals numbers rather than names. How has that attitude changed throughout your career, from scientific detachment to this emotional involvement with the animals?

I was very lucky, because I had a professor who specialized in facial expressions. Like Darwin, he worked on chimpanzees and other primates, and he was one of the few people open to the idea of emotions in animals. I learned to talk about these issues by listening to him. He was a very funny man and very open-minded. I grew up in a time when people didn't want to talk about animal emotions or animal thinking. Even something like animal cognition had to be put in quotation marks. Nowadays we say that chimpanzees laugh because they make laughing sounds. When I got started, I was instructed to call it vocalized panting or something like that.

Darwin didn't have that hang-up. In his books he talks about how he would go off into the zoo and ask the keeper to tickle the monkeys or the apes. And he would go home, tickle his eight children and then would say, “Oh, they laugh, they seem to laugh too.” He was much freer than we are.

Yeah, Darwin was much freer in the nineteenth century. Then, in the twentieth century, we got B. F. Skinner. Skinner had what we often jokingly call “physics envy.” He wanted the field to be as strict and as hard-nosed as physics and chemistry. That's why they're called behaviorists, because they only allowed themselves to talk about behavior and nothing else. According to them, animals didn’t think, they didn’t feel, they didn’t plan, and they weren’t conscious, nor sentient. It's only now that we're sort of wrestling away from this sort of thinking.

How does animal sex factor into all of this? Do you think that’s been systematically misunderstood?

When dogs mate, we say that they’re breeding, when really they’re just having sex. We translate all of it into reproductive terms, but there's pleasure involved. All female mammals have a clitoris. The dolphin and the bonobo have the biggest clitorises, and they happen to also be the two species that have a lot of extra sex. Why would all females have a clitoris if pleasure was not an issue?

Female sex, generally, has been grossly underestimated. We first learned that females had a lot of extra sex beyond reproduction by studying birds. People had always idealized these monogamous birds and assumed that all of the eggs from their nests were fathered by the same male. Then we started to do DNA testing on the eggs, finding that many were coming from different fathers. The only possibility that the biologists of that time could imagine—and they wrote this in their papers—was that the females must have been raped by another male. We now know from more careful studies that the females actually go out of their way to find other fathers. They travel away from the nest, they start shouting and yelling so that males come to them, and that's how they get eggs from these males.

In primate studies, the same sort of thing happened. We always assumed that the alpha male would by far have the most offspring, and so in a monkey group, the alpha male would have more than 90% of the babies. Then we started doing paternity testing and found that a lot of other matings were happening—things that we didn't see because they happened at night or behind the bushes. The alpha male has more offspring than other males, but he doesn't have the 90%. He gets just a bigger proportion.

What do we know about the male ability to nurture?

When human males become fathers, their testosterone drops and they develop more oxytocin. There was a landmark Israeli study of men who were the primary caretakers of children, and it showed that their brain changed entirely—their amygdala became bigger, and effectively their brains actually became more maternal.

And how does this work in non-human animals?

There was a study done in the 1950s where they took babies away from macaque mothers and put them in a group with adult males. They compared them later, after several years, with young monkeys who had been raised by their own mothers. They could not find a difference—the males had done a very good job raising those kids, carrying them, holding them, all of that.

How does gender diversity affect the field itself? You have said that when you started in the field there were mostly men, and now there are many more women primatologists. Do female primatologists bring a different point of view or a different set of interests to the field?

It's a different set of interests, not a different science. When I was a student, the field was mostly men, and now it’s around 75% women. The women came in and were interested in family relationships, in child care, in female choice, and how partners choose each other, whereas the men had been mostly interested in hierarchies and violence and territoriality.

If you look at a baboon troupe, the males are twice the size of females, so male primatologists originally described the baboon troupe as male dominated. However, we now know that the female kinship network is the center of the group. So yeah, the female primatologists brought a very different perspective, and female choice was also a very important issue because it turned out that female hierarchies had a great say in who would mate with whom.

Your next book is about how our understanding of animal behavior has changed. How has it changed in your lifetime?

When I was a student, animals were machines, stimulus response machines, or in ethology—where I came from—they were instinct machines, and so animals had no mind, they had no emotions, their inner life was completely denied. Now, almost every week, a new discovery is made regarding bumblebees imitating each other, or chimpanzees having a theory of mind, and so on. The whole perspective has changed. If I said now that animals have no emotions, they’re just machines, people in the audience would revolt. Thirty years ago, there would have been a lot of nodding.

One hundred years ago, Wolfgang Keuler pissed off the behaviorists tremendously by saying that animals could think. He would hang a banana very high, and give his chimps sticks and boxes. After a while, some of them would pick up the sticks and the boxes, and stack them up to reach the banana. He realized they must have solved the problem in their head. This was anathema to what the behaviorists were saying, but now we have many interesting examples of this kind of insight.

I saw a beautiful example in some recent research. If you give a plastic tube to an ape with a peanut at the bottom, they will try to reach in or shake it out. Some of them will go to the water faucet, take a sip and spit it into the tube, until the peanut floats up, and they can take it out. This is a very interesting solution, because the tool is not given to them—they have to imagine it. This is a challenging task for most human children.

I can compare your studies to my own observations of chickens, who have distinct personalities, too.

Yes, you even see it in fish. I recently visited a lab where they kept zebrafish. When you tap on the tanks, you see that some are shy, moving to the back of the tank, while others are bolder—they rush forward.

It’s probably harder to understand the in-betweens. I have the same problem with my chickens. I recognize the chicken that always gets out of the coop and runs into the house, and the other one that is always running away. I recognize the extreme behavior, but there are probably a lot of gray areas.

I also always thought familiarity was essential to this kind of understanding. I'm an actress, and sometimes I think about what I can bring as an actress to animal behavior. Acting is relating to another person, channeling empathy and establishing the feelings of a text with other actors. I can say that I love you, but my body language can say that I hate you. That kind of empathy must be essential to working with animals, and to understanding them.

Yeah, it's absolutely essential. I know some scientists who work on primates and try to keep their distance, but then the primates often don't want to perform or are not interested in the task, because there's no mutual interest. The best scientists I've had in my lab are the ones who are very “chimpy,” who act like chimps and relate to them. The chimps become their friends. I think that's true for many animals.

Esther Segretto, 2023.Courtesy of the photographer

Can we learn from them?

Of course, we can learn from them. We don't need to act like bonobos, necessarily. In this room, all these people are sitting together without fighting and without sex, which wouldn’t necessarily happen in the primate kingdom. But our relationship with nature is actually a big problem. Philosophy and religion have given us this separation, placing us above and beyond nature, and this is coming back to bite us.

I thought of that after the COVID crisis when all the people were so happy to see each other and touch and embrace, because we couldn't do that for about 18 months. That really showed our primate nature. We're not happy with having just digital contact on a little screen. We want to smell and feel and be up close to each other, which is very primate-like.

At the primate center where I work, we had an outdoor area for our chimpanzee colony. We decided to build a new climbing frame, and so we spent two weeks creating a big frame that was high enough to look all over the landscape. We were very proud of what we did. For two weeks, we locked up the chimps in buildings and separated them in little cages. When we released them, we thought they’d be thrilled to see the climbing structure, that they’d race up there and be impressed by what we had done. Instead, for the first two hours, they didn’t look at the structure at all. They were all embracing and kissing and hanging out and grooming and having sex. They were so happy to see each other after two weeks of being locked up. That's a bit how I felt after the COVID crisis. People were really thrilled to see each other. It showed our primate nature.

It is great to be back with all of you. Thank you, Frans. ♦

This conversation took place on May 11th, 2023, as part of our Author Talks series. Watch the full interview here.