Orangutan poop holds surprising clues about how long they breastfeed - Popular Science

June: Welcome to Kindred Minds — I'm June, a primatologist and your guide to some of the most surprising, moving, and genuinely mind-expanding true stories from the world of our closest relatives. Every episode, we pull back the curtain on primate life and discover just how much of ourselves we see looking back. And today's episode is a good one — I promise. Before we dive in, a warm thank you to our sponsors: Ada, who helps clients integrate A I into their real-world workflows; Ago Consulting — pronounced "Ahh-Go" — silicon development consultants working across everything from A I to SoC; and Zen Semiconductor, an umbrella company with a remarkable portfolio spanning the silicon industry. We're grateful for their support. Today we're visiting the rainforests of Borneo, sitting in on a very unusual experiment with monkeys and a banana casino — yes, you heard that right — and we're traveling back tens of millions of years to rewrite what we thought we knew about where primates first came from. The thread running through all of it? Just how alike we truly are. June: Let's start with cognition — with intelligence — and with one of the great apes that I find endlessly fascinating: the orangutan. Now, orangutans live mostly solitary lives. If you've read anything about them, that's probably one of the first things you encountered. Adult males in particular roam vast stretches of rainforest largely alone. So for a long time, researchers assumed that complex social learning — the kind that requires watching others, copying strategies, building relationships — just wasn't really their thing. Chimps got the headlines for culture and tool use. Orangutans were seen as the quiet loners. But that picture has been changing, and a study that's been making the rounds recently adds another beautiful piece to the puzzle. It turns out orangutan mothers actively arrange what scientists are describing as jungle playdates for their young. I love that framing, because it's so immediately recognizable. These mothers are deliberately steering their offspring toward other young orangutans — seeking them out, positioning themselves so their babies can interact and play. This isn't accidental overlap. Researchers observing wild orangutans in Borneo documented mothers making choices — social choices — that gave their youngsters time with peers. And why does that matter? Because play is how young primates learn. It's how they practice negotiating, reading faces, managing frustration, building the social muscles they'll need for the rest of their lives. We do the same thing, don't we? We take our kids to the park. We set up playdates. We understand intuitively that children need other children. And here are orangutan mothers, in the dense canopy of a Bornean rainforest, operating from what looks like exactly the same understanding. The social brain — the part of us that knows connection is necessary — it's not a human invention. It's much, much older than us. June: And while we're with the orangutans, I want to tell you about another piece of research that sounds almost comically unglamorous but is actually brilliant science. Researchers have been studying orangutan breastfeeding duration using, of all things, poop. Specifically, they're analyzing the chemical signatures in fossilized and fresh orangutan feces to understand how long mothers nurse their young. Now, the reason this matters is that breastfeeding duration in primates is a window into life history — how fast or slow a species develops, how much energy and time mothers invest in each offspring. And orangutans already hold a record among non-human primates: they have the longest inter-birth interval of any mammal, meaning they wait the longest between having babies. A mother orangutan might nurse a single infant for six, seven, sometimes even eight years. Eight years. Think about that investment. The poop-based research is helping scientists nail down exactly how that timeline works in wild populations, where you can't exactly follow a mother and child around with a clipboard for a decade. What you can do is collect samples and read the biochemical story they tell. Zinc and barium isotopes, it turns out, leave a record in teeth and hair of when an animal was nursing and when it wasn't — and that signal shows up in what gets excreted too. It's painstaking, unglamorous, and genuinely ingenious science. And what it reveals is a portrait of motherhood that takes your breath away a little — this enormous, decades-long commitment to a single young life. June: Now I want to take you somewhere completely different — to a monkey reserve, and to one of the most inventive experiments in primate cognition research I've come across recently. Scientists working with capuchin monkeys set up what Nautilus magazine called, brilliantly, an A I-powered banana casino. I want to explain what that actually was, because the reality is as interesting as the name. Capuchins are already famous for being exceptionally smart — they use stone tools in the wild, they've been observed cracking nuts and tubers with rocks for what appears to be thousands of years of cultural tradition. They're curious, they're bold, and they're very motivated by food. So researchers gave them access to a system — essentially a touch-screen device with A I behind it — where they could make choices and receive rewards. A kind of slot machine, in banana terms. What the experiment was probing is something economists and psychologists have studied extensively in humans: how we make decisions under uncertainty, how we respond to risk, how we weigh a guaranteed small reward against a gamble for a bigger one. And the capuchins? They showed the same systematic quirks that humans do. They were loss-averse — losses stung more than equivalent gains felt good. They were drawn to gambles in ways that weren't always rational by a pure expected-value calculation. Sound familiar? This is the stuff of behavioral economics — the research that won Daniel Kahneman a Nobel Prize when applied to human decision-making. And here it is, showing up in monkeys at a banana slot machine in a reserve. The architecture of how we think about risk, reward, and loss — it isn't something culture built from scratch in humans. It's something evolution handed down, deep in our primate lineage, long before we had stock markets or insurance policies or anything else to apply it to. June: Which brings me to our second thread — our shared biological recipe. Because what the banana casino study is really pointing at is something profound about what we are, at the level of our D N A and our neural wiring. Here's a number I come back to often: humans and chimpanzees share somewhere between ninety-eight and ninety-nine percent of their D N A. Depending on how you count — coding genes versus the full genome — the figure shifts a little, but the ballpark is staggering. We are not like chimpanzees the way a car is like a bicycle. We are like chimpanzees the way one human being is like another human being, except a little more different. The instructions that build a brain, wire up a nervous system, calibrate an emotional response, structure a social hierarchy — those instructions are almost identical across the great apes. And it's not just chimps. Orangutans share roughly ninety-seven percent of their D N A with us. Even more distantly related primates — capuchins, macaques — share the deep structural blueprint for a primate brain. The genes that regulate dopamine, the neurotransmitter at the heart of reward and risk — virtually identical across primate species. Which is exactly why capuchins playing a banana casino produce data that tells us something real about human decision-making. We're not projecting human traits onto animals. We're recognizing that the traits were never exclusively ours to begin with. June: And this shared recipe extends further than behavior. The same D N A that shapes our social instincts also shapes our bodies, our development, our motherhood. The reason an orangutan mother nurses for seven years and a human mother nurses for — well, it varies widely across cultures, but often one to three years, sometimes more — the reason the timescales differ is partly about body size, brain size, and the particular demands of each species' ecological niche. But the underlying biology, the hormonal cascade of oxytocin and prolactin that bonds a mother to her infant, that suppresses ovulation during nursing, that makes the cost-benefit math of reproduction so consequential — that's the same machinery. Built from the same recipe. Expressed in the canopy of Borneo and in maternity wards in Seoul and São Paulo and Nairobi. We keep drawing the line between human and animal as if it's a clean break, but biology keeps showing us it's a gradient, a continuum, a family tree with living branches — not a ladder with us at the top. June: Now let's go back in time — way back — because our third thread today is a story that quietly rewrites the origin story of every primate alive, including us. For decades, the prevailing assumption in paleontology was that primates evolved in the tropics. It made intuitive sense: look at where they live today — rainforests, tropical woodlands, warm and humid places. The biodiversity of the tropics seemed like the cradle of primate life. But a new analysis of fossil evidence, including some remarkable finds from a place in Wyoming called Smiley Draw, is challenging that assumption in a serious way. The fossils from Smiley Draw are small, fragmentary things — teeth, mostly, and some jaw bones — but teeth are incredibly informative. Their shape, their size, the enamel thickness, the cusps: these are the fingerprints of diet and evolutionary lineage. And what researchers are finding at Smiley Draw deepens a picture that's been quietly building: that some of the earliest primates — animals from the Paleocene epoch, roughly sixty to sixty-five million years ago — may have lived in environments that were far cooler and more seasonal than we imagined. Not arctic tundra, but not tropical jungle either. Temperate, variable, sometimes cold. Wyoming, sixty million years ago, looked nothing like Wyoming today — the continent was in different positions, the climate was warmer globally — but the fossil evidence suggests early primate ancestors were more ecologically flexible than we gave them credit for. June: Why does this matter beyond the wonderfully nerdy satisfaction of revising a textbook? It matters because it changes how we understand the origins of primate adaptability — including human adaptability. One of the things that makes primates distinctive as a group is that we can live almost anywhere. There are Japanese macaques sitting in hot springs in the snow. There are baboons in the Ethiopian highlands at altitude. There are humans in the Arctic and in the Sahara. That flexibility — that ability to read an environment, learn from it, adjust behavior, use cognition to compensate for what instinct alone can't handle — maybe it was baked in from the very beginning. Maybe the earliest primates weren't creatures perfectly tuned to a stable tropical paradise. Maybe they were already problem-solvers, already flexible, already using their relatively large brains to navigate an unpredictable world. And if that's true, then the intelligence we see in a capuchin at a banana casino, or an orangutan mother steering her baby toward a playmate, or a human being figuring out how to stay warm in a Wyoming winter sixty million years later — maybe all of that is one continuous story. One lineage, one recipe, one long experiment in how far a big brain and a social nature can take you. June: And that brings me to a moment I want to end on — a true story that I think ties all of this together beautifully. A few years ago, a wildlife rescue team in Borneo — right where our orangutan mothers are scheduling those jungle playdates — was working to relocate a mother orangutan and her infant who had been displaced by deforestation. The translocation process is slow and careful; you sedate the animal, you monitor her vitals, you move her and her baby together because separating them, even briefly, causes visible distress in both. The researchers documented something that stuck with me. As the mother was coming out of sedation, groggy and disoriented, she reached out and wrapped her arm around her infant before she was even fully conscious. Before she knew where she was. Before she could assess the situation. Her first instinct, in the fog between sleep and waking, was to hold her baby close. I don't think you need a degree in primatology to know exactly what that feels like — to recognize it as something deep and real and shared. That reflex isn't cultural. It isn't learned from a parenting book. It's written in the D N A, in the same ancient recipe that writes it in us. These are not creatures that are almost like us. They are our family. And what happens to them happens, in some sense, to us too. June: So — what a day. We've followed orangutan mothers through the forest canopy, watched capuchins outsmart a banana slot machine, dug through ancient Wyoming soil for the teeth of our earliest ancestors, and found ourselves, as always, looking into a mirror that's millions of years old. The intelligence and the feeling we value so much in ourselves — they were never ours alone. They belong to this whole, extraordinary, aching-to-survive family of primates that we are lucky enough to be part of. That's what Kindred Minds is here to celebrate. This episode is brought to you by Ada, Ago Consulting, and Zen Semiconductor — and I'm genuinely grateful for their support in helping these stories reach you. If today's episode moved you or surprised you or made you want to know more, please subscribe wherever you listen, share it with someone you think would love it, and check the link in show notes for the research and articles behind everything we talked about today. I'm June. Stay curious, stay connected — and I'll see you next time.