Short Wave - What Fossilized Poop Can Teach Us About Dinosaurs

Episode Date: November 24, 2023

Walking into Karen Chin's office at the University of Colorado, Boulder, one of the first things you might notice is that petrified poops are everywhere. They're in shallow boxes covering every surface and filling up shelves, cabinets and drawers. She's a leading expert in the fossils, known as coprolites. They delight her because of what they reveal about the ancient eating habits and food webs of dinosaurs — rare insights for the paleontology world. This episode, she talks with Short Wave co-host Aaron Scott about the lessons scientists can learn from ancient poopetrators.Interested in learning more ancient or scatological mysteries of science? Email us at [e-mail] — we might cover it on a future episode!See pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences.NPR Privacy Policy

You're listening to Shortwave from NPR. Hey, shortwavers, Aaron Scott here, and today we are going to talk with Karen Chin about the incredible scientific importance of dinosaur poop. I became interested in fossilized feces when I was working for paleontologists, Jack Horner. Jack Horner is the renowned Montana paleontologist who discovered a whole bunch of things about dinosaur growth and behavior, and inspired one of the main scientist characters in Jurassic Park. Mutated the dinosaur genetic code and blended it without a frogs. I learned that somebody had found fossilized feces, and I thought that was just the weirdest thing.

So I ran to Jack, and I asked to see it. This was the late 80s. Karen was a grad student, and she was responsible for cutting into the fossilized dinosaur bones to look at things like blood vessels. So I asked if I could make a thin section of the fossil feces. And he said, yes. And when I looked through a microscope, I could see plant cells that were ingested 75 million years ago by a dinosaur.

And it blew my mind because I thought, man, this is how you can learn about interactions between dinosaurs and plants and other organisms. Karen is now one of the leading experts on dinosaur feces. She's a professor of geological sciences and the curator of paleontology at the University of Colorado. And she's even the subject of a recent children's book called The Clues Are in the Pooh. As you mentioned, Jack Horner was famously an inspiration for Jurassic Park. And Jurassic Park, in the first movie, portrayed mountains of dinosaur dung that were as tall as a human. That is one big pile of shit.

I'm guessing that's an exaggeration, but how big are we talking when it comes to dinosaur dung? Okay, the largest specimens I've examined are on the order of about six liters in volume, which is pretty large. A leader being a court, that pile, when I saw the movie, I thought that was rather humorous, but it actually made sense because if you have a dinosaur in a zoo, they're going to be producing so much dung. and what are the zoo keepers going to do with it, but pile it up in one place so somebody could cart it off later.

So today on the show, Karen Chin shows us just how much we can learn about dinosaurs by digging through their fossilized don't. Best part, we're going to get hands-on. You're listening to Shortwave, the science poopcasts from NPR. Knock knock. Hello, nice to meet you. I'm Erin. Erin, nice to meet you. The first thing you notice when you walk into Karen Chin's office is that dino poops are everywhere.

They're in shallow boxes covering every surface and filling up shelves, cabinets, and drawers. These are all from the two medicine formation, which is... I asked Karen to see one of the fossils that got her started. First, she pulls on some plastic gloves. And it sounds funny. I got to protect these species, but you do want to do that. And then she opens one of the locked cabinets. This is the one I wanted to show you.

She places the box on the desk and picks up a piece of petrified poop, which is officially called a coprolite. It's a word that stems from Greek and literally means dungstone or poop rock. They kind of just look like black rocks. They don't have the sausage shape that you would expect to see of fossil feces. they're kind of angular That's because Well, they had a hearty distance to fall from the dinosaur to the ground

and likely broke on impact You can see that some of them have bits and pieces of plant tissues in them Also in them Some strange finger-shaped formations of different colored sediment that looked like tunnels or burrows of some sort Karen was intrigued enough

by the question of what we could learn from these fossil feces that she decided to investigate them as her doctoral thesis. I was contacted by a dung beetle expert in Canada, Dr. Bruce Gill. And he said, I hear you have burrows in dinosaur coprolates. Do you think they could be dung beetle burrows? And I said, they're burrows, but I don't think I could tell them from a worm burrow or another kind of burrow. So she sent him some photos. And when I next heard from him, he was very excited.

He said, these can't be anything else. That's because the burrows weren't empty, like something had dined and dashed. They'd been backfilled with the light-colored dirt from the ground the dung was sitting on. And then the dark-colored dung, in turn, had been buried into a burrow in the ground below. And this is very diagnostic of dung beetles, because dung beetles are the only living organisms we know to stash. organic matter into burrows like this where they would have laid their eggs in what we call dung sausages. And this dung sausages would be just the right size to nurture a growing baby dung beetle. And did I read that at this point we didn't actually have any evidence that dung beetles were around that early, correct?

That's right. That's right. This was some of the first evidence that we had. have that dung beetles had a relationship with dinosaurs back in the Cretaceous. And all of this eating leads us to the question. And once you have a sample, how do you figure out who dung it? Yes. You look at which animals had bones or other skeletal things in the same sediments in which you find the coprolites. then you can kind of look at their feeding habits, look at the functional morphology,

what kind of teeth did they have? Are their living relatives that have certain behaviors and dietary preferences? But I have to say, in some cases, we won't ever know who actually produced it or who was the pupa trader. But to me, when I, as a paleoecologist, it may not be the most important.

thing to know exactly who produced it. If you can tell who was eaten and think about some generalized food webs in the ancient environment, you can get a feeling for what that environment was like. And this is another reason why I like coprolite so much because they're basically like receipts of transactions of carbon resources. or traveling through an ecosystem. So you just have this evidence of this ancient transaction. So this mystery is really interesting to me because I feel like when we go to a museum

or watch a show like prehistoric planet, it looks like scientists know a lot about the dining habits of different dynos, but you can't really tell that from looking at their skeletons. So is this information all gathered from, analyzing their poop? Well, a lot that we infer that it appears in movies like Jurassic Park about dinosaurs are based on what we know of behavior of living animals. So we look at elephants, rhinos, and we think, well, maybe dinosaurs actually behaved like them. And they mooseed around

different landscapes and just peacefully fed on the vegetation. And I think those inferences, probably there's a lot of truth to them. But what I like about studying dinosaurs is that we've been finding some things that were surprising. And my favorite began with these same coprolites. I did my doctoral thesis on in part where we found evidence for dung beetles. And that was a first, so that was exciting. But about 10 years after I published that, I remember thinking about what the dinosaurs ate,

why was there so much wood in their feces? That was perplexing because herbivores today can't digest the cellulose in wood because wood cells are held together by a tough glue-like substance called lignin. But Karen was clearly seeing broken down wood in their feces. So her idea was maybe they weren't eating healthy trees. Maybe they were eating rotting wood. White rot fungi can actually destroy the lignin. And if they do that, that increases the digestibility of wood 30 to 60 percent.

Because animals, there's more cellulose in there that can be digested by bad. bacteria. So this meant these dinosaurs had been feeding on rottingwood. It was really surprising. You just don't hear of that behavior in modern animals. At least Karen says not in the large mammals scientists were using as stand-ins for dinosaur feeding habits like elephants and rhinos. But then again, dinosaurs weren't mammals. They were a lot more like birds. So my hypothesis was that because we found these coprolites in the nesting grounds of dinosaurs, that the dinosaurs had to change their diet when they were reproducing. And we see that in modern dinosaurs. So birds that are seed eaters will have to change their diet to a insect eating diet

when they're getting ready to lay eggs because they have to provide protein. for the yolks. And they also have to increase their calcium intake because they have to provide calcium for the shells. And it seemed like, boy, if you're maybe a 25-foot-long duck-bill dinosaur and you suddenly need to get a lot of protein, you know, you're not going to be like a D-Rex chasing after animals

or anything. But you could find a predictable source of protein in rotting wood in the form of insects. sex, crustaceans, worms, all kinds of things that would be hanging around rotting wood. So just to bring this back around, this was exciting because these are the kinds of things we can't learn from just looking at a bone. Fossil poop isn't just waste material, but when we hold a piece of fossil poop, this is telling us about eating interactions between. organisms about recycling processes when you have detritus that gets recycled and is used again by

other organisms. So when you're holding a piece of fossil poop, that really shows us how dynamic life has been, not only today, but in the past. Karen Chin, thank you so much for talking fossil feces, dino dung, petrified poo. However we're going to call it, thank you for discussing it with us. much, my pleasure. Before we go, we know you enjoy hearing about new discoveries and the science behind the headlines from us here on Shortwave. And we wanted to remind you that your financial support is what makes our work possible. Because the thing is, even though our journalism is freely available, it's not free to produce. So a big shoutout is in order for our Shortwave Plus supporters and anyone listening who currently donates to public media. Thank you. You are

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Thank you. This episode was produced by Burley McCoy and edited by our managing producer Rebecca Ramirez. It was fact-checked by Britt Hansen. Our audio engineer was Maggie Luthar. Beth Donovan is our senior director, and Anya Grundman is our senior vice president of programming. I'm Aaron Scott. Thanks as always for listening.