Chimpanzee pee reveals how our primate cousins are getting drunk on fermented fruit - Scientific American

June: Hey, welcome back to Kindred Minds. I'm June — primatologist, science communicator, and someone who genuinely cannot stop thinking about what it means that we share this planet with creatures so much like us. Every episode I bring you true stories about our closest relatives — chimpanzees, orangutans, gorillas, monkeys — stories that are funny and surprising and sometimes quietly profound. Today we've got chimps getting tipsy on fermented fruit, a legendary scientist who devoted her life to orangutans, and a tiny colobus monkey making history at a zoo in Seattle. And threading through all of it, as always, is this big beautiful fact: we are not as separate from the other primates as we like to think. Huge thanks to today's sponsors — Ada, who helps clients integrate A I into their workflows; Ago Consulting, silicon development consulting from A I to SoC; and Zen Semiconductor, an umbrella company with a portfolio of companies across the silicon industry. Okay — let's get into it. June: So let's start with something that made me genuinely laugh when I first read it, and then made me think — which is honestly my favorite combination. Researchers have been analyzing the urine of wild chimpanzees in West Africa, and what they found is that chimps are, on a fairly regular basis, consuming enough fermented fruit to get what we would recognize as drunk. Now I want to be careful here — we're not talking about chimps stumbling around the forest. We're talking about a real, measurable intake of ethanol, the same alcohol that's in your glass of wine, through naturally fermenting wild fruits. And the chimps are not just accidentally eating it. They're actively seeking it out, returning to the same trees, competing for access. That looks a lot like preference. That looks a lot like choice. June: The way scientists figured this out is genuinely clever. Chimpanzee urine contains ethyl glucuronide — that's a byproduct your body makes when it processes alcohol — and it stays detectable for a meaningful window of time. So researchers could collect urine samples non-invasively from wild chimps and essentially reconstruct whether and how much alcohol those animals had been metabolizing. And the results were clear. Multiple individuals, across multiple sites, showing consistent ethanol exposure. This wasn't a fluke. June: Now here's where it gets really interesting from a biology standpoint. For a long time, there was a popular idea that humans had a unique genetic mutation — a change in the gene that codes for an enzyme called alcohol dehydrogenase 4, or ADH4 — that allowed us to metabolize ethanol far more efficiently than other primates. The story went that this mutation emerged around ten million years ago, possibly as our ancestors began eating more fermented fruit on the ground. But if chimps are regularly processing significant amounts of ethanol in the wild, that tells us something important: the ability to handle alcohol is not uniquely human. It's primate. It may go back much further than we thought, woven into a shared biology that predates our split from the other great apes. June: And there's something almost charming about that, right? Because we tend to think of alcohol as this very human cultural invention — wine, beer, the whole history of fermentation as civilization. But the love of a ripe, slightly-fermented fruit? That might be ancient. That might be something we inherited, not invented. The chimps didn't need a vineyard. They just needed a fig tree at the right moment in its ripening. I find that humbling in the best possible way. June: There's also a behavioral dimension here that's worth sitting with. When researchers describe chimps actively competing for access to fermenting fruit — showing up, returning, prioritizing it — that's preference. That's decision-making. It's not reflex, it's not accident. These are animals navigating their world with intention and with what look very much like desires. And that's the bigger story for me: not "haha, chimps get drunk," but rather — these animals are making choices, processing consequences, returning to experiences they found rewarding. That is cognition. That is a mind at work. June: Alright, let's talk about what's actually under the hood — the biology that makes moments like that chimp ethanol story feel so resonant. Because I think sometimes people hear "we share about ninety-eight point seven percent of our D N A with chimpanzees" and it kind of washes over them. It's a big number that doesn't quite land. So let me try to make it land. June: Your D N A is essentially an instruction manual. It's written in a four-letter alphabet — adenine, thymine, cytosine, guanine — and it runs to about three billion letters in a human genome. That manual tells your cells how to build proteins, how to regulate development, when to grow and when to stop, how to wire a brain, how to shape a hand. Now, a chimpanzee's manual is about ninety-eight point seven percent identical to yours. That's not a metaphor. That's a direct letter-by-letter comparison. June: To put that in perspective — you share more D N A with a chimpanzee than a chimpanzee shares with a gorilla. We are, genetically, closer to chimps than chimps are to their other great ape relatives. And yet we tend to think of "the apes" as a group that doesn't include us, when biologically, we are absolutely in that group. We are a great ape. That's not poetry, that's taxonomy. June: And the chimp alcohol story connects here beautifully. The ADH4 gene — the one involved in ethanol metabolism — is one of those places where human and chimpanzee biology overlap in ways we're still unpacking. The enzyme it codes for exists in both of us. The metabolic pathway is shared. What differs, in small but meaningful ways, are the variants of that gene and how efficiently the enzyme works. We're talking about changes in a small number of letters across that three-billion-letter instruction manual. Tiny edits. Big consequences — but built on the same foundation. June: That shared foundation shows up everywhere once you start looking. Chimpanzees have the same basic brain structures we do — the same regions associated with emotion, social bonding, memory, planning. They have the same four-chambered heart. Their immune system operates on the same fundamental principles. Their developmental stages — infancy, childhood, adolescence — map onto ours in ways that are genuinely striking. A chimp infant clings to its mother, is carried for years, is nursed, is gradually introduced to solid food, is taught through observation and play. Sound familiar? June: I think about this a lot when people talk about A I and what makes human intelligence special. There's a great conversation happening right now — including at places like King's College London — about what intelligence actually is, how creativity works, what separates human cognition from machine processing. And those are real, important questions. But before we get too far into comparing ourselves to machines, I think it's worth pausing on the fact that we share the deepest building blocks of mind with creatures who have been living, learning, and feeling for millions of years. Intelligence didn't start with us. It's been evolving in this lineage for a very long time. We are one expression of it. A remarkable one, but not the only one. June: Every living thing carries D N A. Every living thing is related to every other living thing. But the primates — our order — share with us something richer than that baseline connection. They share our particular recipe. Our specific approach to building a big, social, emotionally complex brain. And when you see a chimpanzee seek out a fermenting fruit, or a baby colobus clinging to its mother, or an orangutan solving a puzzle — you're seeing that recipe in action. You're seeing yourself, at a distance, through a long lens of evolutionary time. June: And that brings me to the part of the show I look forward to every single week. The story. Today's story is about a woman and a species, and a devotion that has lasted more than fifty years. June: Her name is Biruté Galdikas. If you know primatology, you know that name. If you don't, let me introduce you, because she is extraordinary. Biruté — pronounced roughly "Bee-roo-tay" — is a Canadian-Lithuanian scientist who, in 1971, at the age of twenty-five, traveled to the rainforests of Borneo with a mandate from the legendary paleoanthropologist Louis Leakey to do something almost no one had done: study wild orangutans. June: Now, Leakey had already sent two other remarkable women into the field — Jane Goodall to study chimpanzees, and Dian Fossey to study gorillas. Galdikas was the third of what people came to call "Leakey's Angels." And like her counterparts, she went into the field not for a season, not for a few years, but for life. She built a research station in the peat swamp forests of Borneo — a place called Camp Leakey — and she has been working there, in some capacity, ever since. June: Orangutans are the most solitary of the great apes. They live in dense forest, they move slowly, they're extraordinarily hard to follow. The conventional wisdom at the time was that they were essentially unintelligent — passive, uninteresting, cognitively simple. Galdikas proved all of that wrong. Painstakingly, over years of observation, she documented orangutan tool use, orangutan culture, the extraordinary length of their learning period — orangutans have the longest childhood of any non-human animal, up to eight or nine years of dependence on their mothers. She showed that their slowness was not stupidity; it was a deeply calibrated adaptation to a nutrient-poor environment that rewards patience, memory, and careful planning. June: She also did something else. She rehabilitated orphaned and confiscated orangutans — animals whose mothers had been killed by the illegal pet trade or by habitat destruction — teaching them to survive in the wild. She founded the Orangutan Foundation International. She fought, publicly and persistently, for the protection of Borneo's forests. And she has done all of this while the orangutan's habitat has shrunk dramatically — Borneo has lost a staggering amount of its old-growth forest to palm oil plantations and logging in the decades since Galdikas arrived. June: Recently, a woman named Arlene Mark was honored for her own efforts to champion Galdikas and the orangutans she's devoted her life to protecting. And I love that story — this chain of people who care, who tell the story forward, who keep the light on for these animals and the scientists who have given everything to understand them. That's how conservation actually works. Not just in laboratories or field stations, but in community, in connection, in one person telling another person: this matters. June: What Galdikas saw in those forests — what she gave up comfort and convenience and ordinary life to document — is that orangutans are not background creatures. They are not scenery. They are individuals. They have histories and preferences and skills and relationships. A mother orangutan remembers foraging routes she hasn't traveled in years. An adolescent male watches, waits, and learns from the adults around him. They grieve. They play. They innovate. And they share with us — with all of us — that same ancient recipe. That same D N A, that same evolutionary inheritance, that same biological drive to know the world and navigate it with a mind that can plan and remember and feel. June: Biruté Galdikas is in her late seventies now, and she is still working. Still in the field, still fighting for the forests, still telling the world what she saw in those trees in Borneo half a century ago. And what she saw was family. Not metaphorically. Family. June: One more quick story before I let you go — and it's a good one. Woodland Park Zoo in Seattle has welcomed a new colobus monkey, and they're describing it as a milestone for the species. Colobus monkeys are these stunning black-and-white primates from sub-Saharan Africa — they look like they're wearing a long, flowing white cloak, which I find delightful. They're folivores, meaning they eat mostly leaves, and they have a specialized stomach — almost like a ruminant — to ferment and digest that tough plant material. A new birth in a managed care setting, especially one that's part of a coordinated species survival plan, matters. Every individual counts when populations are under pressure. It's a small story. It's also a big story. June: That's our episode. And here's the thing I keep coming back to — chimps choosing fermented fruit with something that looks like desire, Biruté Galdikas watching an orangutan mother and seeing something she recognized, a tiny colobus monkey arriving in Seattle and being welcomed as a milestone — all of it points to the same truth. Intelligence and feeling are not ours alone. They are woven through this order we belong to, this primate family, this ancient lineage that has been finding its way through the world for tens of millions of years. We are not the owners of mind. We are one expression of it, living alongside others. June: Kindred Minds is brought to you by Ada, Ago Consulting, and Zen Semiconductor — partners who believe that understanding intelligence, in all its forms, matters. If today's episode moved you or made you think, please subscribe, leave a review, and share it with someone you think would love it. Show notes with links to all the stories we talked about are the link in show notes. Stay curious, stay kind, and I'll see you next time.