Wild chimps consume more alcohol than anyone expected

June: Welcome to Kindred Minds — I'm June, a primatologist who has spent her career falling more in love with our closest relatives every single year, and this show is where I get to share that love with you. We tell true stories here — stories about the other primates, about what they think and feel and do, and about how startlingly much we have in common with them. Today's episode is a good one. We're going to meet a bonobo who played pretend like a child, think about why chimpanzees might be natural drinkers in a way that goes all the way back in evolutionary time, and say a proper goodbye to one of the most remarkable individuals — not most remarkable animals, individuals — science has ever had the privilege of knowing. Before we dive in, a huge thank you to our sponsors: Ada, who helps clients integrate A I into their workflows in ways that actually make sense for their business; Ago Consulting — that's "Ahh-Go" — silicon development consulting covering everything from A I to SoC; and Zen Semiconductor, an umbrella company with a remarkable portfolio across the silicon industry. We're grateful for their support. Now — let's go meet our family. June: So let's start with something that genuinely changed how I think about chimpanzee communication, because I think a lot of us carry around this vague idea that chimps make noise — hoots, screams, some gestures — and that it's expressive but ultimately pretty simple compared to what we do with language. And researchers have been chipping away at that assumption for decades. But recent work has pushed things significantly further, and I want to walk you through what they actually found, because the details are where the wonder lives. June: Researchers studying wild chimpanzees in places like the Taï Forest and Budongo have been doing something painstaking and brilliant — they've been cataloguing not just individual calls, but combinations. The question they were really asking is: does chimp communication have structure? Do combinations of calls mean something different from the individual calls on their own? And the answer, it turns out, is yes. Chimpanzees use what researchers describe as a compositional system — meaning they combine calls in ways that create new meanings. That is genuinely significant. That is a feature we associated almost exclusively with human language. June: Think about what compositionality means for us. The words "dog" and "bite" mean specific things. "Dog bites man" means something. "Man bites dog" means something different. The combination, and the order, carry information beyond the parts. Now, chimps aren't writing sentences, let's be clear. But the principle — that you can build new meaning by combining signals — is present. And that's a much deeper kind of communication than a fixed alarm call that means "eagle." This is flexible. This is generative, to a degree. June: What I find especially striking is what this implies about the evolution of language. We've long known that the physical apparatus for speech — the larynx, fine motor control of the tongue — developed late in our lineage. But the cognitive architecture for combining signals into meaning? It looks like that might be much, much older. It might be something we inherited, not invented. The building blocks of language may have been in the primate toolkit long before any human opened their mouth and tried to name the world. That reframes everything, doesn't it? June: And here's the thing about studying this — it requires enormous patience and enormous respect for the animals as communicators. You have to sit with them, record them, resist the urge to project human meaning, and also resist the urge to dismiss what you're seeing. It's a narrow path, and the researchers walking it are doing something important. They're not saying chimps have language. They're saying the cognitive foundations for language have deep roots — roots that run through us and through them, tangled together in a shared evolutionary past. June: Now I want to turn to something that caught my eye this week and made me laugh with recognition before it made me think harder. Chimpanzees, it turns out, are consuming alcohol on a fairly regular basis — not because anyone gave it to them, but because ripe, fermenting fruit is part of their natural diet, and ripe fermenting fruit contains ethanol. This isn't new as an observation — we've known chimps sometimes eat overripe fruit — but what's new is the careful measurement of just how much ethanol that actually adds up to. June: Researchers have done the math, and it is striking. The amount of alcohol a chimpanzee can ingest through their ordinary daily fruit-eating can be equivalent to roughly one to two human alcoholic drinks per day. That is not a tiny incidental exposure. That is regular, meaningful contact with ethanol, happening naturally, in the wild, as part of a normal foraging day. This is what scientists call the "drunken monkey" hypothesis, first proposed by biologist Robert Dudley, and this research strengthens it considerably. June: The idea is this: for our primate ancestors, and for many primates today, ethanol wasn't a human invention or a cultural artifact. It was a natural signal in the environment. Ripe fruit ferments. Fermented fruit contains ethanol. And ethanol, crucially, has a smell. A strong, distinctive, diffuse smell that travels further on the air than most other fruit signals. So the ability to detect and follow that smell — and to be motivated by it, to find it rewarding — would have been genuinely useful for a fruit-eating primate trying to locate ripe food. June: Our shared attraction to alcohol, in other words, may not be a human weakness or a cultural accident. It may be an ancient primate adaptation, a sensory system tuned over millions of years to say: follow that smell, there's ripe food there, go get the calories. The enzyme that breaks down ethanol in our liver — alcohol dehydrogenase — we share a version of it with other great apes, and there's evidence that a key mutation making it much more effective at processing ethanol arose in the ancestor of humans, chimps, and gorillas roughly ten million years ago. Right around the time our ancestors were spending more time on the ground, where fallen, fermenting fruit would have been abundant. June: I love this story because it does what good science always does — it takes something that feels uniquely human or uniquely modern, and it reaches back through time and shows you the root. Our relationship with alcohol didn't begin at a bar or in a vineyard. It began in a forest, with a primate following their nose to a pile of ripe, sweet, slightly fizzy fruit. That ancestor is in us. And they're in the chimps still foraging in the Taï Forest today. Same recipe. Same ancient appetite. Same nose pointed toward the smell of something good to eat. June: And that brings me to our shared recipe — because the more I learn about chimpanzee communication, chimpanzee behavior, chimpanzee biochemistry, the more I want to just sit with the number. Chimpanzees and humans share somewhere between 98 and 99 percent of our D N A. Depending on how you measure — coding regions, non-coding regions, insertions and deletions — the precise figure shifts a little. But the ballpark is staggering. Less than two percent of the genetic text separates us. Less than two percent. June: That two percent, though — it's not nothing, and I don't want to wave it away. Two percent of a genome of three billion base pairs is still tens of millions of differences. Evolution is sensitive. Small changes in regulatory regions — the parts of the genome that control when and where and how much of a protein gets made — can have enormous downstream effects. The difference between a human brain and a chimpanzee brain isn't written in wholly different genes. It's written in the timing and dosage and expression of largely the same genes. June: But here's what I find most moving about the ninety-eight percent. It means that everything we're talking about today — the compositionality in chimp communication, the alcohol metabolism, the capacity for imagination and pretend play — these aren't chimps accidentally stumbling toward human abilities. These are expressions of a shared biological heritage. The same D N A that builds a human brain capable of language also builds a chimpanzee brain that combines calls into meaningful sequences. The same liver enzymes that process our evening glass of wine are working in a chimp digesting a fallen fig. We are running variations on the same program. June: And that shared program extends to things we don't always think about. Immune responses. Hormonal systems. The architecture of emotion — the same circuits for fear, for attachment, for social reward, for grief. The neurochemistry of oxytocin and dopamine and serotonin doesn't look radically different across the great apes. When a chimpanzee mother holds her infant and her oxytocin rises, the same molecule is doing the same job it does in a human mother holding her newborn. This is not metaphor. This is biochemistry. The same ancient instructions, copied and carried forward through fifty, sixty million years of primate evolution, still running in all of us. June: I think about this when people ask me whether animals "really" feel things — whether primate emotions are "real" emotions or just behavior that looks like emotion from the outside. And my answer is always: look at the substrate. Look at the D N A, the hormones, the neural architecture. If the hardware is ninety-eight percent the same, if the molecules are the same, if the circuits are the same — on what grounds do we say the inner experience is absent? That is a claim that requires an enormous amount of justification. And I've never heard a convincing one. June: Now. I need to talk about Kanzi. June: If you've spent any time in the world of primate cognition, you know this name. Kanzi was a bonobo — a male bonobo who was born in 1980 and lived until earlier this year, when he passed away at the age of forty-four. And his life was one of the most extraordinary scientific stories of the twentieth and twenty-first centuries. He was studied at the Great Ape Trust in Iowa — later called Ape Cognition and Conservation Initiative — and what he did over his lifetime genuinely shifted what scientists believed was possible for a non-human mind. June: Kanzi learned to use lexigrams — symbols on a keyboard — to communicate. Not through formal training, actually. He learned by watching his mother, Matata, who was the one being formally taught. Kanzi was just present, a youngster hanging around, and he absorbed it. That itself is remarkable — incidental learning, the way a child picks up language by being immersed in it, not by being drilled. He went on to develop a vocabulary of hundreds of symbols, and he used them spontaneously, creatively, to ask for things, comment on things, and express preferences. June: He made stone tools. Not imitating a step-by-step demonstration — he figured out the technique of striking flint to create sharp flakes, which he then used. This was a technology we thought distinguished early humans from all other species. Kanzi did it. June: And then there's the pretend play. There are documented accounts of Kanzi engaging in imaginative play — pretending that objects were other things, treating a stuffed animal as if it were real, acting out little scenarios. When researchers analyzed this behavior carefully, they found it had the hallmarks of what we see in human children around two to three years old — intentional, symbolic, imaginative. He wasn't responding to something in front of him. He was creating a fiction and playing inside it. That is a form of imagination. That is mental simulation of something that isn't there. June: Kanzi died in 2025, and the scientific community mourned him the way you mourn a colleague — which is exactly the right instinct. He wasn't a subject. He wasn't a specimen. He was an individual with a personality and a history and a body of work, in the most honest sense. He was curious, he was social, he had preferences and dislikes. He liked watching movies. He liked certain foods. He had relationships with the humans around him that lasted decades. Researcher Sue Savage-Rumbaugh, who worked with him for most of his life, has spoken about what it was like to grow old alongside him — the depth of a relationship built across species lines over forty years. June: And here's the thing I keep coming back to. Kanzi wasn't an exception that proved the rule. He was a window. He showed us what bonobo cognition is capable of under the right conditions — with the right enrichment, the right relationships, the right opportunity to express what's already there. The capacity for symbolic thought, for imagination, for tool-making — it didn't enter Kanzi from outside. It was in him. It was in his D N A, his bonobo brain, his primate heritage. He showed us a version of bonobo intelligence that had always been there, waiting for the context to show itself. June: That's what I think about when I hear people say "but he was raised around humans, it's not natural." And I understand the scientific caution — it's legitimate, it's important. We need to know what's spontaneous in the wild versus what's facilitated in captivity. But the underlying capacities are not installed from outside. They are inside. Kanzi didn't borrow imagination from humans. He had it. He showed it to us. We just finally got close enough to see. June: Goodbye, Kanzi. Forty-four years. What a life. What a mind. What a gift — to science, to everyone who knew him, and to every human who heard his story and felt, maybe for the first time, that the line between us and them is not a wall. It is a gradient. A long, slow, living gradient. And we are all somewhere on it together. June: So here we are at the end of another episode, and I always leave these conversations feeling the same thing — this quiet, grounding sense of company. We are not alone on this planet. We are not alone in our intelligence, not alone in our capacity to feel, not alone in our need to connect and communicate and imagine. The chimps combining calls in the forest, the bonobos playing pretend, the ancient primate ancestors following their nose to fermenting fruit — they are our family. The same D N A, the same evolutionary story, the same basic biological recipe, carried forward together across millions of years. That's not a small thing. That's everything, really. June: Kindred Minds is brought to you by Ada, Ago Consulting, and Zen Semiconductor — and I'm so grateful for their support in helping us tell these stories. If today's episode moved you or taught you something or made you see a chimp or a bonobo a little differently, please share it with someone you love. Subscribe wherever you get your podcasts, leave us a review if you're feeling generous — it genuinely helps people find the show. And check the link in show notes for sources and further reading on everything we talked about today. Stay curious, stay kind, and I'll see you next time.