What snow monkeys’ steamy baths are really doing to their bodies

June: Welcome to Kindred Minds — I'm June, a primatologist and your guide through the extraordinary world of our closest relatives on this planet. Every episode, I bring you true stories about the other primates — stories that I think will surprise you, move you, and maybe make you see yourself a little differently. Today we've got a genuinely wonderful lineup: ancient fossils that are rewriting what we know about our deepest primate roots, a brand-new monkey species with the most spectacular orange lips you've ever seen, and some fascinating science about what Japanese macaques are really getting out of their famous hot spring baths. Before we dive in, a warm thank you to the sponsors who make this show possible — Ada, who helps businesses integrate A I into their workflows in ways that actually make sense; Ago Consulting — that's "Ahh-Go" — silicon development consultants who work across everything from A I to full system-on-chip design; and Zen Semiconductor, an umbrella company with a whole portfolio of businesses across the silicon industry. We're grateful for all three. Now — let's talk primates. June: So let's start with cognition — with behavior — because I want to tell you about the Japanese macaques, and I promise this story is weirder and more wonderful than you might expect. Most people have seen the photos. These monkeys — also called snow monkeys — sitting in steaming volcanic hot springs while snow falls around them. It looks like a spa day, and honestly, it kind of is. But here's what researchers in Japan have been quietly digging into: what are those baths actually doing — not just to their comfort levels, but to their biology? And the findings are genuinely surprising. Scientists studying groups of macaques at hot spring sites found that the monkeys who regularly bathed showed differences in lice patterns compared to the ones who stayed out of the water. Now, your first instinct might be — well, of course, the hot water probably kills parasites. And that might be part of it. But what really caught researchers off guard was this: sharing those crowded, warm pools didn't seem to increase the spread of parasites the way you'd predict. When animals huddle together in warm, wet conditions, conventional wisdom says that's a recipe for transmission — for things to jump from one body to another. But that wasn't what they were seeing. The baths may actually be doing something protective. And then there's the gut microbiome angle — the community of bacteria living inside these animals — which also showed subtle differences between bathers and non-bathers. Now, we have to be careful here, because this is early science. We're not yet at the point of saying the hot springs are definitively reshaping their gut health. But the signal is there, and it's worth paying attention to. What I find so compelling about this story is what it tells us about culture in animals. Because here's the thing — bathing in the hot springs isn't instinct. It's learned behavior. The first macaque to wade into those pools did something novel, and other macaques watched, and copied, and over generations it became a tradition. A cultural practice, passed down within that group. Not every population of Japanese macaques does this — only the ones near hot springs, and only after they figured it out socially. That is culture. Not human culture, but culture in the truest sense of the word — a behavior that spreads through learning and observation, not through genes. And now it turns out that cultural practice might actually be changing their biology. Their invisible microbial world. That is a remarkable loop — from curiosity, to behavior, to tradition, to physiology. These are not simple creatures running on pure instinct. They are animals with social lives complex enough to generate and sustain cultural practices across generations. Sound familiar? June: That brings me to our second thread — what I call our shared recipe. Because what the snow monkey story quietly points to is something that runs all the way through primate biology, and honestly through all of life — the idea that we are built from very similar instructions. And today I want to connect that to something that genuinely stopped me in my tracks this week. Fossils from a site called Smiley Draw in Wyoming are adding new detail to one of the most extraordinary chapters in the history of life on Earth — the very early evolution of primates. We're talking about creatures that lived tens of millions of years ago, right around the time when the primate lineage was just beginning to branch and diversify. These fossils are giving paleontologists new windows into what those early relatives looked like, how they moved, what their teeth tell us about what they ate, and crucially — how they fit into the family tree that eventually produced every primate alive today, including us. Now, I want to be careful here because the details of early primate paleontology are genuinely technical and the science is still developing. But the big picture is this: every time we find fossils like these, we add another chapter to a story that began over sixty million years ago, when small, tree-dwelling mammals started developing the traits we now recognize as distinctly primate. Grasping hands. Forward-facing eyes that give you depth perception. Relatively large brains for body size. Nails instead of claws. A tendency toward social living. These traits didn't appear all at once — they assembled slowly, over millions of years, in countless small steps. And here's where I want you to feel the weight of something: those ancient Wyoming creatures carried versions of the same genetic toolkit that we carry today. The same basic D N A architecture. The same developmental programs that build a primate body. When you look at the roughly ninety-eight to ninety-nine percent of D N A that we share with chimpanzees — which is one of the most extraordinary facts in all of biology — you're looking at the accumulated result of that sixty-million-year journey. Most of the recipe stayed the same. Most of the instructions that build a primate — the wiring for social bonding, for learning, for emotional response — those instructions are ancient and shared. And the fossils from places like Smiley Draw are showing us just how far back that shared recipe goes. What moves me about early primate paleontology is that it collapses the distance between us and every other primate alive today. We didn't arrive from somewhere else. We grew out of the same lineage, shaped by the same pressures, running on the same biological software — just with different updates applied over millions of years. June: And that brings me to something that arrived in the science news this week that I think lands beautifully in this conversation about our shared recipe — and it's about behavior, not bones. A study that's been making the rounds suggests that same-sex sexual behavior in primates likely predates the emergence of humans — that it's not something unique to our species, not something that requires a special cultural explanation, but something that appears to be a genuinely ancient feature of primate social life. Now, same-sex behavior has been documented in a remarkable number of primate species — bonobos, Japanese macaques, gorillas, many others — and for a long time, researchers have been trying to understand what it means evolutionarily. The short answer is: it's complicated, and we're still learning. But the key finding that this research points to is that when you map same-sex behavior across the primate family tree, the pattern suggests it was present in common ancestors — that it's not a quirk that evolved independently over and over again, but rather something that has deep roots. And I think that's a profound reframe. Because it means this is part of the primate condition. Part of the ancient behavioral repertoire that we share with our relatives. It's in the recipe. And that matters — because it situates human experience within the broader fabric of primate life, rather than treating it as an outlier or an anomaly. We are primates. Our behaviors — the full range of them — exist within a context that is millions of years old and shared across dozens of species. That is not a small thing. June: Now, I want to close today with a story that made me genuinely giddy — and this is our meaningful primate-and-people story — because sometimes the news delivers something that is just pure joy. This week, researchers announced the discovery of a new species of monkey in the forests of Africa — and these animals have the most astonishing, vivid orange lips. I mean, we're talking a color so bold and distinctive that it almost looks painted. The species had been, in the words of the researchers, hiding in the forest — present but unrecognized, not yet formally described by science. And that phrase gets me every time: hiding in the forest. Because it's a reminder of how much we still don't know. We are in the twenty-first century, with satellites and genomic sequencing and decades of field research, and there are still monkeys we have never formally described. There are still chapters of the primate story we haven't read yet. Now, the discovery of a new primate species is genuinely rare. We're not talking about insects or beetles, where new species turn up constantly — primates are large, relatively visible animals that have been studied intensely. So when a new one is formally recognized, it's significant. It means scientists either found something in a region that hadn't been surveyed carefully, or — as is increasingly common — they used genetic analysis to distinguish what looked like one species but turned out to be two. And either way, what it means practically is urgent: a newly recognized species often has a very small population, a restricted range, and needs immediate conservation attention. The moment you name a species, you also begin assessing its risk. And these orange-lipped monkeys are almost certainly going to need our help. That's the bittersweet edge of discovery stories like this one — the wonder of meeting someone new, and the immediate weight of responsibility. I love that the researchers used the word "exciting." Because it is exciting. There is something deeply human about the thrill of discovery, about encountering a form of life we didn't know existed. And I would argue that thrill is itself primate in nature — that curiosity, that pull toward the new, that social excitement of saying "look what we found" — those are ancient impulses we share with the animals we study. There's also something beautiful about the fact that this species chose its hiding spot so well. These forests have been home to these monkeys for what must be thousands of generations, and they have simply been living their lives, unclassified, unbothered by our naming systems. They existed before we found them. They didn't need our recognition to be real. But now that we've found them — now that we've seen those extraordinary orange lips and said yes, you are your own kind — we have a responsibility that goes with that recognition. That is the primate-and-people contract, I think. Discovery comes with obligation. June: I want to leave you with one thought before we go, and it connects everything we talked about today — the snow monkeys passing down their hot spring culture, the ancient fossils from Wyoming, the deep roots of primate behavior, and those orange-lipped monkeys living quietly in the forest. The through-line in all of it is this: we are not as separate as we like to think. Intelligence is not ours alone. Feeling is not ours alone. Culture, curiosity, social bonds, a rich inner life — these things were not invented by humans. They were inherited. We are the latest chapter in a story that started sixty million years ago, running on a recipe that is mostly shared, expressed in dozens of different ways across dozens of extraordinary species — all of us alive right now, on the same planet, at the same moment. That is worth paying attention to. That is worth protecting. This has been Kindred Minds, brought to you by Ada, Ago Consulting, and Zen Semiconductor. If today's stories sparked something in you, please share this episode with someone you think would love it — and subscribe so you never miss a story. Show notes with links to all of today's science are in the link in show notes. Stay curious, stay connected, and I'll talk to you next time.