The Twelve-Gorilla Nettle Experiment - Improbable Research

June: Welcome to Kindred Minds. I'm June, a primatologist and science communicator, and this show is my love letter to our closest relatives — the other primates — told through true stories that I think will genuinely surprise you. Every episode, we pull back the curtain on what these animals think, feel, and do, and what that tells us about ourselves. 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 make sense; Ago Consulting — that's "Ahh-Go" — silicon development experts working across everything from A I to full system-on-chip design; and Zen Semiconductor, an umbrella company with a remarkable portfolio spanning the silicon industry. We're so glad to have them with us. Now — today on the show: gorillas and stinging nettles, a brand new monkey species just discovered deep in the Congo, what a bonobo named Kanzi can tell us about the origins of imagination, why brain size turns out to be a surprisingly poor measure of primate smarts, and a story about gorilla mothers and grief that I have been turning over in my mind for weeks. The thread running through all of it? How alike we truly are. Let's go. June: Okay, so let's start with intelligence — and I want to begin by dismantling something most of us just assume is true. We tend to think bigger brain means smarter animal. It's intuitive. It feels logical. And for a long time, scientists leaned into it. But a study that's been making the rounds recently throws a serious wrench into that idea, at least when it comes to primates. Researchers found that brain size, on its own, does not reliably predict cognitive performance across primate species. Not in the way we assumed. And I want to sit with that for a second, because it's genuinely paradigm-shifting. What the researchers found is that the relationship between brain and intelligence in primates is far more nuanced — it's not just about volume, it's about organization, about neural efficiency, about which specific regions are developed and how they're connected. A bigger hard drive doesn't mean a faster computer if the architecture isn't right. And primates have evolved an astonishing variety of cognitive solutions, many of them elegant and sophisticated, in brains that wouldn't win any size competitions. Think about that. We've been measuring the wrong thing, or at least not the whole thing. And this matters beyond academic curiosity — it means when we look at a small monkey or a mid-sized ape and assume we know how smart they are based on how big their head is, we are probably selling them short. We've been doing that for a long time. So what does predict intelligence in primates, if not raw brain size? Researchers point to things like relative neocortex size — that outer layer of the brain involved in higher-order thinking — social complexity, ecological challenges, and the demands of finding and processing food. Primates who have to remember where hundreds of fruit trees are, navigate complex social hierarchies, and solve novel problems every single day — they develop the cognitive tools for it, regardless of whether their brain would impress you on a scale. And then there's this: the twelve-gorilla nettle experiment. I love this story. It sounds almost like the setup to a joke, but it's real science, and it beautifully illustrates that intelligence lives in behavior, not in brain mass. Researchers observed gorillas — twelve of them — dealing with stinging nettles, which are genuinely painful plants. And rather than just grabbing them and wincing, or avoiding them entirely, the gorillas had developed specific techniques for folding and handling the nettles in ways that minimized contact with the stinging hairs. It's careful, learned, deliberate behavior. Not instinct. Technique. The kind of thing you figure out, maybe watch others do, and then refine. That's cognition in action. That's a gorilla being smart in exactly the way a gorilla needs to be smart. And no brain-size chart would have told you to go look for it. June: Now let's talk about the biology underneath all of this — the shared recipe. Because when I say we are related to other primates, I don't mean it metaphorically, or philosophically, or in some vague "we're all connected" sense. I mean it in the most literal, molecular, biochemical way possible. Our D N A — the instruction manual for building and running a human body — is approximately 98 to 99 percent identical to that of chimpanzees. Ninety-eight to ninety-nine percent. That is not a small overlap. That is almost the same book with a few different chapters. We share around 97 percent with gorillas, and somewhere in the high 96s with orangutans. These are not distant cousins. These are close family. And it shows up everywhere — in our physiology, our neurology, our immune systems, our emotional architecture. When a gorilla shows fear, the same stress hormones flood her body that flood yours. When a chimpanzee bonds with a friend, the same oxytocin — sometimes called the bonding hormone — is involved that's involved when you hug someone you love. The biological machinery is the same machinery. Now, here's where the brain-size story connects back beautifully to the shared recipe. The genes that govern brain development — particularly the genes associated with the neocortex, with synaptic plasticity, with the wiring of neural circuits — are remarkably conserved across primates. We share them. We inherited them from common ancestors who lived tens of millions of years ago. What's different between a human brain and a chimpanzee brain is not some entirely alien ingredient — it's more like a variation on a theme. Some genes are expressed differently, some regions expanded, some connections more elaborate. But the recipe is the same recipe. Scientists sometimes call it "deep homology" — the idea that the same underlying genetic toolkit gets deployed in different proportions across species. A gorilla's capacity to learn a technique for handling nettles, a bonobo's capacity for imaginative play, a monkey's ability to navigate a complex social group — these don't emerge from nowhere. They emerge from a biological inheritance that we share. When I look at the discovery of a new monkey species in the Congo — which we'll get to in a moment — one of the things that moves me about it is the reminder that there are still members of our extended family out there that we haven't even met yet. Still animals carrying variations of that same ancient D N A recipe, living lives of their own in forests we've barely mapped. That's not just a scientific fact. It's a kind of wonder. June: And speaking of members of our extended family we haven't met — let me tell you about the new monkey discovered deep in the Congo rainforest. Researchers have identified what appears to be a new species of African monkey, found in one of the most remote and biodiverse regions on the planet: the Congo Basin. Now, new primate species discoveries are genuinely rare. We're not talking about finding a new beetle or a new fungus — primates are large, visible, studied. The fact that one has remained unknown to science until now speaks to just how vast and unexplored those rainforests still are. The Congo Basin is the second-largest tropical rainforest in the world, and it is extraordinary — a place where biodiversity runs so deep that science is still catching up. Details on this particular species are still emerging, but the discovery itself is a reminder that the primate family tree has branches we are still finding. And it raises urgent questions about conservation. Because the same remoteness that allowed this monkey to remain undiscovered is also fragile. Forests get fragmented. Habitats shrink. A species can slip toward vulnerability before we've even had a chance to understand it. But let me bring it back to something even more immediate and human — and that's the story I want to end with today, because it's the one that has stayed with me the most. It comes from the Dian Fossey Gorilla Fund, the organization that has been studying and protecting mountain gorillas in Rwanda for decades — the organization that grew out of Dian Fossey's own life's work. The story is this: gorilla mothers, when they lose an infant, will sometimes continue to carry the body. For days. Sometimes longer. And researchers have been studying this behavior, trying to understand what it tells us. Now, I want to be scientifically careful here, because it's easy to project human grief onto animal behavior and overclaim. But what the science does say is striking. This behavior — carrying a deceased infant — is documented across multiple great ape species, including chimpanzees and gorillas. It is not random or rare. It appears to be a real, consistent response to loss. Researchers at the Fossey Fund have noted that the mothers who do this are not confused about their infant's condition. They are not acting as though the baby is simply sleeping. The behavior seems to be something else — something that looks, from the outside, like an unwillingness to let go. Like mourning. I think about a gorilla mother in the green hills of Rwanda, carrying her infant, and I think about the 98 percent of D N A we share with her. I think about the oxytocin that flowed when she bonded with that baby, the same molecule that flows in us. I think about the fact that attachment, and its loss, is written into primate biology in a way that goes back millions of years. We didn't invent grief. We inherited it. And so did she. That's not metaphor. That's biology. That's kinship. And then there's Kanzi. Kanzi was a bonobo — one of the most remarkable individual animals ever studied. And researchers, in work that's been written up in Smithsonian Magazine, explored whether Kanzi could engage in something that looks like pretend play — specifically, imaginary tea parties. Having a pretend cup of tea. Treating an absent object as present, assigning it properties it doesn't have, playing a social role in a fictional scenario. This is something human children do around age two or three, and it's considered a significant cognitive milestone — a sign that the child can hold a mental representation of something that isn't literally there. And Kanzi did it. He engaged with researchers in pretend scenarios. He participated in the fiction. He understood the game. Now, there is ongoing scientific discussion about exactly what this means and how far it extends — researchers are careful and rightly so. But the direction of the evidence is clear: the cognitive roots of imagination, of play, of pretend — they are not uniquely human. They go deeper than us. They belong to the primate lineage we share. Kanzi passed away in 2024, and the loss was felt deeply by the researchers who had worked with him for decades. That grief, too, felt familiar. Because it was. June: So here's where I land at the end of every episode, and honestly, every day I spend in this field: intelligence isn't ours alone. Feeling isn't ours alone. The capacity for curiosity, for attachment, for grief, for play — these are primate inheritances, shared across our family in ways that science keeps confirming, layer by layer. We are not apart from nature. We are nature, in the same way a gorilla is, a bonobo is, a newly discovered monkey in the Congo is. Same ancient recipe, beautiful variations. This has been Kindred Minds, brought to you by Ada, Ago Consulting, and Zen Semiconductor — three teams of people doing genuinely interesting work, and we're grateful for their support. If this episode moved you or made you think, please subscribe, share it with someone you love, and leave us a review — it genuinely helps more people find the show. And check the link in show notes for more on all the stories we covered today. Stay curious out there. Our family is waiting.