Teeth smaller than a fingertip reveal the first primate ancestor

June: Welcome to Kindred Minds. I'm June, a primatologist who has spent her career falling more and more in love with our closest relatives — and then trying to find the words to share that love with anyone who'll listen. Today's episode is one I've been sitting with for a while, because the stories we're covering hit differently. We lost two giants this week — two beings who changed how the world understands what it means to be a primate, and what it means to connect across species. We're also going back deep — way, way back — to the very first creature you could call a primate ancestor, and asking why kissing might be older than you ever imagined. Big thanks to today's sponsors: Ada, who helps clients integrate A I into their workflows; Ago Consulting — that's "Ahh-Go" — silicon development consulting from A I to SoC; and Zen Semiconductor, an umbrella company with a portfolio of companies across the silicon industry. Now settle in, because today's through-line is simple and staggering at once: we are more alike than we know, and we always have been. June: Alright, let's start with cognition — and I want to begin with a name. Kanzi. If you've spent any time in the world of primate research, you know that name. And if you haven't, I need you to understand that Kanzi was a bonobo who did something that most scientists once thought was impossible. He learned to communicate with people using a symbol board — a lexigram, it's called — covered in geometric symbols, each one representing a word. And he didn't just learn to point at symbols to get food. He understood spoken English. Not perfectly, not the way you and I do, but studies showed he could respond correctly to novel spoken sentences he had never heard before, sentences like "put the ball in the water" or "give the cereal to the dog." Novel sentences. Ones that weren't trained. That's not mimicry. That's something much more interesting. June: Kanzi was born in 1980 at the Yerkes National Primate Research Center, and he came to language almost by accident — he was watching his adoptive mother being trained on the lexigram system, and one day researchers realized he had been absorbing it all. He'd essentially taught himself. And from there, his abilities only grew. He used symbols to plan ahead. He asked for things that weren't in front of him. He made tools — actually knapping flint to create sharp edges, which was thought to be a uniquely human skill. He did it by watching a human demonstration and then figuring out his own method. His own method. He didn't just copy — he problem-solved. June: What researchers like Sue Savage-Rumbaugh and her team documented over decades was that Kanzi's comprehension of language, tested rigorously and blindly, was comparable to that of a two-and-a-half-year-old human child in certain respects. Now, I want to be careful here — that comparison has nuance, and the field has ongoing debates about what exactly language comprehension means across species. But the point stands: Kanzi demonstrated symbolic thought. He held concepts in his mind that weren't physically present. He used them to communicate intention. And he did it with warmth. People who worked with him described him as curious, playful, emotionally sensitive. He grieved. He had favorites. He had moods. Kanzi passed away in 2024, and the primate cognition world paused. Because he wasn't just a subject. He was a collaborator. A communicator. A reminder that the line between us and our ape relatives is not a wall — it's a gradient. June: And that gradient goes back a very, very long way. Which brings me to our second thread — our shared recipe — because I want to tell you about a creature so small you could hold its remains on the tip of your finger, and yet it is, in a very real sense, us. Or at least, it's where us began. June: Paleontologists have just announced the discovery of fossils belonging to Purgatorius — yes, that's the actual name, named after Purgatory Hill in Montana where the first specimens were found — in Colorado's Denver Basin. Now, Purgatorius is the earliest-known relative of all primates. All of us. Every monkey, every ape, every lemur, every human being on this planet traces its lineage back through something like this tiny, shrew-sized, tree-dwelling mammal. And until now, we thought Purgatorius was largely confined to Montana and parts of Canada. These new fossils push the range significantly southward and tell us that this little creature spread fast after the asteroid impact that ended the dinosaurs, roughly 66 million years ago. June: Let that sink in for a second. The dinosaurs vanish — and within a geologically tiny window of time, our earliest primate ancestor is already on the move, already diversifying, already pushing into new territory. These fossils are just teeth, by the way. Tiny, millimeter-scale teeth. But teeth are extraordinary records. The shape of a cusp, the angle of an enamel ridge — these things tell paleontologists what an animal ate, how it lived, what branch of the mammal family it belongs to. And these teeth say: primate. These teeth say: you. June: Because here's what I find so moving about this. When we talk about D N A — about the fact that you and a chimpanzee share somewhere around 98 to 99 percent of your D N A sequence, or that you and a bonobo like Kanzi are more closely related to each other than either of you is to a gorilla — it can feel abstract. Big numbers. But Purgatorius makes it visceral. There was a moment, 66 million years ago, a tiny furry creature in a forest that had just gone very, very quiet after the asteroid hit, and it survived. And it moved. And it diversified. And down one long, branching, winding road, there's a bonobo pointing at a lexigram board. And down another, there's you, listening to a podcast. Same road at the start. Same recipe. The instructions of life written in D N A that we have been sharing and refining and passing on for tens of millions of years. That's not a metaphor. That's molecular biology. June: And speaking of the deep past — I have to mention Gigantopithecus blacki, because this story has been making the rounds and it deserves a moment. This was the largest ape that ever lived. We're talking an animal that may have stood close to three meters tall and weighed somewhere in the range of 200 to 300 kilograms. It lived in what is now southern China, and it survived for about two million years before going extinct, likely sometime around 300,000 years ago. Now here's the mystery: we don't have a skeleton. We have thousands of teeth and a handful of jaw fragments — that's it. And recent research, including work using ancient protein analysis, has been trying to piece together where exactly Gigantopithecus sits on the primate family tree. It appears to be a relative of modern orangutans, but a very distant one. And the best current evidence suggests it went extinct because it was a specialist — it relied heavily on forest fruit, and when the climate shifted and those forests changed, it couldn't adapt. Two million years on this planet, and then gone. That haunts me a little. It's a reminder that even the largest, most successful lineages are not guaranteed. Adaptation is everything. June: Okay. I need to take a breath here, because the next part of today's episode is the one I've been turning over in my mind all week. And I want to give it the space it deserves. June: Jane Goodall has died. She was 91 years old. And I say that sentence and I feel the weight of it, because Jane Goodall was not just a scientist. She was the reason many of us became scientists. She was the reason the public started caring — truly caring — about chimpanzees. About what they feel and think and lose when we destroy their habitat. June: Let me take you back to 1960. Jane Goodall is 26 years old, no formal university training at that point, and she walks into Gombe Stream in what is now Tanzania with a notebook and a pair of binoculars and an almost reckless level of patience. The chimpanzees flee from her for months. Months. Most researchers would have given up, or shifted methods. She just kept coming back. Sitting at a distance. Letting them get used to her. And then, one October morning, she watches a chimpanzee she has named David Greybeard — and the naming itself was controversial, because scientists weren't supposed to name their subjects — she watches David Greybeard strip the leaves from a grass stem and use it to fish termites out of a mound. Tool use. In a wild chimpanzee. June: She sent a telegram to her mentor Louis Leakey, and his response has become legendary. He wrote back something to the effect of: "Now we must redefine tool, redefine man, or accept chimpanzees as humans." That single observation cracked open a door that has never been closed again. Because if chimpanzees make and use tools — if that behavior is not uniquely human — then what else isn't? And the answer, as decades of research at Gombe and beyond have shown us, is: a lot. Chimpanzees wage war and form alliances. They adopt orphans. They mourn their dead. They have personalities, political relationships, cultural traditions that vary from community to community — groups that crack nuts differently, that groom in different ways, that have different calls. Culture. In the wild. June: Jane Goodall spent 60 years building that case, not just in the forest but in lecture halls and in front of governments and in schools. She founded the Jane Goodall Institute. She launched Roots and Shoots, a program for young people that now operates in over 60 countries. She became, in a way, the most important conservation communicator of the 20th and early 21st centuries. And she did it all with a kind of fierce, grounded optimism that I find — genuinely — hard to match. June: She said once, and I'm paraphrasing here, that every day you have a choice — to act, or not to act. And that if you look at the resilience of nature, and the intelligence of young people, and the human spirit, there is reason for hope. She wasn't naive about the scale of the crisis. She understood it better than almost anyone. But she chose, every single day, to keep going. To keep talking. To keep pointing back at the chimpanzees and saying: look. Really look. June: And there is something so right about the fact that in the same week we lost Jane Goodall, we are also remembering Kanzi. Because in a way, these two beings — a woman and a bonobo — represent the same argument from opposite directions. Jane went to the chimpanzees and showed us they were more like us than we knew. Kanzi reached toward human language and showed us the same thing. The gap is not where we thought it was. The family is larger than we were taught. June: I want to close with something small and wonderful, because I think that's how Jane would have wanted it. Scientists now believe that kissing — the act of pressing lips together as an expression of affection — likely has its roots much further back in our evolutionary history than anyone imagined. Research looking at lip-smacking and mouth-to-mouth contact in our closest ape relatives suggests that something like kissing may go back 20 million years or more, to our shared ape ancestors. Chimpanzees kiss. Bonobos kiss. Orangutans have been observed doing something very similar. It's not a human invention. It's an inheritance. Something passed down through the same long, branching, surviving lineage that began with a tiny tooth in a Colorado fossil bed and runs all the way to you. June: And I love that. I love that one of the most intimate things humans do — something we associate with love, with comfort, with connection — turns out to be ancient. Older than our species. Shared. Because that's what this whole show is about, really. The things we think make us uniquely us — our feelings, our intelligence, our bonds — they didn't appear from nowhere. They grew from something. From someone. From a long line of creatures who figured out how to survive, how to care for each other, how to pass something on. June: We are not separate from nature. We are the latest chapter in a story that started 66 million years ago, in a quiet forest, with a small mammal blinking at a changed sky. And somewhere in that lineage is David Greybeard fishing for termites, and Kanzi pointing at a lexigram, and Jane Goodall sitting very still in the Tanzanian forest, watching, and hoping, and believing that it mattered to pay attention. June: It matters. It always has. June: Thank you for being here with me today on Kindred Minds, brought to you by Ada, Ago Consulting, and Zen Semiconductor. If today's episode moved you — or made you want to know more — please subscribe, and share it with someone you think would care. Show notes with links and sources are at the link in show notes. Stay curious. Stay kind. And remember: these minds we share this planet with — they are not so different from ours. They never were.