Do Monkeys Keep Pets? Study Finds Widespread Primate Interactions With Other Animal Species, From Mice to Deer - Smithsonian Magazine

June: Welcome to Kindred Minds — I'm June, a primatologist who has spent her career falling more in love, every single day, with our closest relatives on this planet. This show is where I get to share that love with you, through true stories about primate intelligence, primate biology, and the remarkable ways that we — humans and our primate cousins — are cut from exactly the same cloth. Today's episode is a good one. We've got a chimpanzee who could read, a brand-new monkey species just discovered in the Congo with the most extraordinary orange lips you've ever seen, and a look at what our tiniest ancient ancestor — whose teeth are smaller than your fingertip — tells us about where we all came from. Before we dive in, a warm thank you to today's sponsors: Ada, who helps businesses integrate A I into their workflows in ways that actually work; Ago Consulting — that's "Ahh-Go" — silicon development consulting spanning everything from A I to SoC; and Zen Semiconductor, an umbrella company with a brilliant portfolio of businesses across the silicon industry. Okay. Let's go meet our family. June: So let's start with cognition — primate minds at work — and I want to tell you about a chimpanzee named Ai. Ai lived at the Primate Research Institute at Kyoto University in Japan, and she was part of one of the longest-running and most extraordinary cognitive research programs ever conducted with a non-human primate. She passed away recently, and when I saw the news, I genuinely had to sit with it for a moment, because Ai's story is one of those that changes how you think about the word "intelligence." Here's what Ai could do. She learned to recognize and use kanji — Chinese characters — as part of a decades-long study into chimpanzee cognition led by Professor Tetsuro Matsuzawa. She could identify colors, numbers, and objects using symbolic representations on a touchscreen. And her memory — oh, her memory. Ai became famous in the scientific world for what's called the "working memory task," where numerals flash on a screen for a fraction of a second — we're talking less than a second — and then disappear, replaced by white squares. Ai could then tap the squares in the correct numerical order, from memory. When researchers tested humans against Ai on this task, the chimpanzee won. Consistently. Young chimpanzees, including Ai's own son Ayumu, showed even faster recall than adult humans. Now, what does that mean? It doesn't mean chimpanzees are "smarter" than us in some global sense — intelligence is not one thing, it's many things, and different species have been shaped by evolution to excel in different cognitive domains. But what it does mean is that the mental machinery for working memory, for symbolic thought, for learning systems of representation — that machinery is not uniquely human. Ai built a relationship with Matsuzawa that lasted decades. She participated voluntarily. She was never coerced. She would sometimes stop a session if she wasn't interested, and sometimes she'd come back and keep going. That's agency. That's a mind making choices. And when you learn that chimpanzees share somewhere in the neighborhood of ninety-eight to ninety-nine percent of their D N A with us, Ai's abilities stop being surprising and start being almost inevitable. She wasn't performing a trick. She was expressing a mind that is, in so many ways, a version of our own. June: Which brings me beautifully into our second thread — our shared recipe. Because what Ai's story really illuminates is something that I think about all the time as a primatologist, and that is the question of what, exactly, makes a human brain different from a chimpanzee brain — and how much those differences actually matter. There's a wonderful piece from the Genetic Literacy Project that recently explored this question, asking: what is it about the human brain that makes us so uniquely capable? And it's a genuinely fascinating puzzle, because when you look at the raw ingredients, we are startlingly similar to our primate relatives. Chimpanzees, bonobos, gorillas, orangutans — these are our closest living relatives, and we share the overwhelming majority of our genetic code with them. With chimpanzees and bonobos, that figure sits at around ninety-eight to ninety-nine percent D N A similarity, depending on how you measure it. Gorillas, around ninety-eight percent. Even with more distant primate cousins — macaques, for instance — we share something like ninety-three percent. The recipe is almost identical. So what changes? Well, a few things. Human brains are larger relative to body size — we have an expanded prefrontal cortex, which is involved in planning, decision-making, and social behavior. We have more complex folding of the cortex, which packs more surface area into our skull. We have differences in the timing of brain development — human brains keep growing and changing for much longer after birth than most primate brains do, which gives us an extended window for learning from our environment. And then there are regulatory genes — genes that don't code for a protein themselves, but control when and how other genes are switched on and off during development. Some of the most important differences between human and chimpanzee cognition may come down not to having different genes, but to the same genes being expressed differently at different times. It's like having the same recipe but changing the oven temperature and the timing — you get a very different result. And then there's a fossil that just knocked my socks off. Scientists recently described tiny fossil teeth — smaller than a human fingernail — that may represent one of our earliest primate ancestors, from roughly fifty-five to fifty-six million years ago. These teeth belong to a creature so small it would have fit in the palm of your hand, and yet the basic primate blueprint is already there — the kind of teeth designed for a mixed diet, the skeletal hints of grasping hands, the forward-facing eyes that give depth perception. All of that, already sketched out, fifty-five million years ago. So when we talk about our shared D N A with other primates, we're not just talking about two modern species that happen to look similar. We're talking about a family that has been writing the same story, with small variations, for tens of millions of years. The primate recipe — curious, social, dexterous, visually sophisticated — is ancient and it is ours, and it belongs to every one of our living relatives too. June: And now I want to tell you something that I think is one of the most quietly wonderful findings in primatology in recent years, because it touches on something so deeply, recognizably human — the impulse to care for another creature that is not your own kind. There's a study, covered recently by Smithsonian Magazine, that looked at interactions between primates and other animal species — not predation, not competition, but something that looks, in some cases, almost like companionship. Researchers catalogued a surprisingly wide range of primates — capuchin monkeys, macaques, and others — engaging in what can only be described as affiliative behavior with other species. Carrying small animals. Grooming them. Keeping them close. Protecting them, even. One of the cases that has received the most attention involves capuchin monkeys in Brazil, who were observed carrying and caring for small rodents — not eating them, not playing with them roughly, but tending to them in ways that looked, at least from the outside, like something approaching attachment. Now, scientists are careful — rightly careful — about the word "pet," because that word carries a lot of human cultural weight, and we don't want to over-anthropomorphize. What's actually going on inside a capuchin's mind when it carries a small rodent around is genuinely hard to know. But what the study makes clear is that this behavior is not a one-off curiosity. It's widespread. It appears across multiple primate species and multiple types of interactions with different animal species, from deer to small mammals. And that pattern matters. Because it suggests that the capacity for cross-species social bonding — for extending care and attention beyond your own group, your own species — may be a much older and more widespread feature of the primate mind than we ever imagined. And here's why that lands so hard for me. Humans do this constantly. We bring animals into our homes. We grieve when they die. We form bonds with creatures that share almost nothing of our biology or our language. And for a long time, that was seen as this uniquely human quirk — a product of our culture, our sentimentality, maybe even our domestication of other animals over ten thousand years. But if capuchins are doing something that rhymes with this, without any of that cultural scaffolding? Then maybe this impulse — this reaching across species lines — is something older. Something that was already present in the primate brain long before humans came along and turned it into civilization. And that, to me, is one of the most beautiful things about studying our primate relatives. They keep showing us that our most cherished, most "human" qualities have roots that go much, much deeper than us. June: I want to close today with something that fills me with pure, uncut joy, and that is the discovery of a brand-new monkey species in the Congo Basin. Scientists recently described a new species — a monkey with strikingly orange lips, found in the dense forests of the Congo — and I love this story so much, because in an era when it sometimes feels like we know everything, the forest reminds us that we absolutely do not. This monkey belongs to the genus Cercopithecus, the guenons, which are already one of the most species-rich groups of African primates — colorful, socially complex, and genuinely beautiful. The new species was identified based on its distinctive coloring, and confirmed through a combination of physical examination and genetic analysis. And the Congo Basin, where it was found, is one of the most biodiverse places on Earth — a vast, ancient, teeming rainforest that is the second largest tropical forest in the world, after the Amazon. Every time a new primate species is described, two things happen in my heart simultaneously. The first is wonder — pure, almost childlike wonder that the world still holds creatures we've never formally met. The second is urgency. Because for a new species to be discovered and immediately need protection is the reality of primate conservation right now. The same habitats that are still yielding new species are also the habitats under the most pressure from deforestation, hunting, and climate change. But I try to hold both of those feelings without letting the urgency swallow the wonder. Because the wonder matters. The fact that there is a monkey, right now, living in the forests of the Congo, with orange lips and a life and a social group and a set of calls that are entirely its own — that is extraordinary. That is the world being more than we thought. And that is exactly why this work matters. Protecting that forest isn't just an environmental project. It's protecting a branch of our own family tree. June: So here's what I want to leave you with today. A chimpanzee who could read Chinese characters. Fossil teeth from our fifty-five-million-year-old ancestor. Monkeys who seem to care for other creatures just for the sake of it. A new species with orange lips, discovered in the heart of Africa. And underneath all of it — the same thread, the same truth: intelligence, memory, curiosity, care, the impulse to bond across difference — none of these things belong to us alone. We inherited them. We share them. And the creatures who share them with us are living, right now, in forests and sanctuaries and research centers, looking back at us with eyes that hold a version of the same light. This is Kindred Minds, brought to you by Ada, Ago Consulting, and Zen Semiconductor — three organizations that understand what it means to invest in intelligence, in all its forms. If this episode moved you or taught you something, please subscribe, leave a review, and share it with someone you love. The more people who feel connected to this living family we belong to, the better chance that family has. Show notes with links to all of today's stories are the link in show notes. Stay curious, stay kind, and I'll see you next time.