Hey, welcome to Sign Stuff, a production of iHeartRadio. I'm hoor hitchhim, and today we're answering the question did dinosaurs have feathers? You might think you know the answer to this question, but as we'll learn today, the real answer has changed significantly in the last few years. To get the full story, we're going to talk to a couple of paleontologies. We're going to tell us what we know about the origin of feathers, which dinosaurs had them, and
why feathers evolved in the first place. I promise by the end you want to look at dinosaurs or feathers the same way again. Enjoy. Hey everyone, So I picked today's topic to celebrate the release of my news book, Oliver's Great Big Universe Evolution Changes Everything. It's all about the history of life on Earth, is told by a kid named Oliver. It's a great book for those smart kids in your life, your nieces or nephews, your friend's kids.
I promise, if they like funny stories and you think they might like science, I think this might be their favorite new book series. So please check it out at Great Big Universe dot net or your favorite bookseller. All right, let's talk about dinosaurs and feathers. Now, I'm excited for today's episode because we're gonna hear from two paletologists, one of whom was involved in the landmark discovery that put the origin of feathers way further back in time than
anyone expected. But before we get there, I thought it was important that we covered the basics first because that's going to help us later in the episode. And the first question we're going to ask is what exactly is a dinosaur? You probably think you know, but according to our first expert, the answer is not that simple. Well, thank you, doctor O'Connor for joining us today.
It's absolutely my pleasure. I'm a big fan, so I'm happy to be here.
Awesome. Can you please tell us who you are and what you do.
My name is Jingme O'Connor, and I'm the associate curator of Fossil Reptiles at the Field Museum of National Street in Chicago. It's just a fancy complicated way of saying that I'm a nerdy dinosaur paleontologist.
I guess maybe for people who are not super familiar. He tell us what exactly is a dinosaur? Like what makes a dinosaur a dinosaur.
Well, okay, that's not an easy question to answer. So dinosaurs are basically a group of animals that have a common ancestor. So, for example, all living mammals have one common ancestor, that's why they form a true group. And mammals are characterized by a specific set of traits that you can then use to identify that they're mammals, like milk and fur. But if only it was so easy
with dinosaurs. Unfortunately, dinosaurs are really weird and different, and until recently we would have said things like dinosaurs have a completely open hip socket and a bunch of traits that for a long time really did define dinosaurs. But then the more we find close relatives of dinosaurs, all those traits we used to use suddenly got blurred. We found that they were present in close non dinosaur animals, or they were absent in the oldest known dinosaurs that we started to find.
All Right, what doctor O'Connor is saying is that the definition of a dinosaur is not an animal that looks a certain way or as a certain characteristic. It just means all the animals that came from one specific common ancestor. Because, as it turns, out, dinosaurs have cousins. Not every big, cool giant reptile is a dinosaur. For example, there are the big reptiles that eventually became crocodiles. Crogs did not
come from dinosaurs. Or those giant swimming reptiles like Ichiosaurus or plesiosaurs that you see swimming around in the Jurassic Part movies. Those are not dinosaurs. There's a big one Terosaurus. These are the giant flying reptiles that you also see in movies, like pterodactyls or Terranodon. But the giant wings and the long deaks dose are not dinosaurs either. They're
more like cousins of dinosaurs. So when you're talking about dinosaurs, you're really talking about a specific family of animals that came from one specific ancestor.
Let's just say that the ancestral dinosaur was probably a small, warm blooded bipedal, probably carnivorous or omnivorous animal.
So scientists think the first dinosaur, the ancestor of the animals we call dinosaurs, probably walked on two legs, kind of like Terrannosaurus REGs or the veloscy raptors that again you see in the Jurassic part movies. But here's a confusing part. Some dinosaurs branched out and went back to walking on four legs, and that's where you get some of the they're famous dinosaurs like Triceratops or the one with the really long neck, Brachiosaurus. All Right, I promise
this will all be useful later. Now let's get to the other basic which is what exactly is a feather.
So my name is Maria McNamara and I am professor of paleontology at University College Cork in Ireland.
Can you tell us what a feather is?
Ah, that's an interesting one. So a feather is basically an integumentary appendage, to give it its scientific term. It's basically made of protein, a protein called keratin. It's the same protein that makes up our hair and nails, and it is actually the most complex sort of tissue structure that is known in vertebrate animals. Each feather has a central sheaft with lateral side branches, and those branches have branches, and actually the branches are organized in a spiral around
the shaft. So a feather is really the most complex tissue structure that is known.
From the skin all right, you probably already knew what a feather was. But here's the thing. That description of feathers only applies to modern feathers. Early feathers, scientists think we're a lot simpler. They look more like hairs, except they're not hairs. How are they related to hairs?
What feathers and hair have in common is that they're both outgroots from the skin, and they're both made of keroten protein. But that's where the similarity ends because hairs, unlike feathers, they don't branch, and hairs are solid. If you slice through a hair and look at us onto the microscope, you'll see a solid cylinder of keroten protein, whereas if you slice through a feather, it's hollow in the middle. So that's one major difference. And also in hairs,
we have a form of keratin called alpha keratin. Alpha kerosin forms a helix, but the kerosion that's in feathers has traditionally been called beta keratin, and that looks like a corrugated tin roof, so it has an up and down zigzag corrugated pattern. So the structure of the proteins is very different.
It makes hair sound a lot more boring.
Hair is still a very interesting structure, but structurally it is simpler than feathers.
So when we talk about dinosaurs, now you know what we mean. And when we talk about feathers, you also know what we mean. And now we get to the question did dinosaurs have feathers? And I'll just tell you the answer to this question is kind of shocking. At least, it really took me by surprise. Where did feathers come from?
Ha? If I could answer that question, I would get I don't know, a normal prize or something.
Yeah, that's good, let's get you noble price.
Yeah. Yeah, Well, look that question, where haven't you feathers come from? That's the question that's been driving our research over the last fifteen years.
All right. According to doctor McNamara, the answer to the question did dinosaurs have feathers? Or where did feathers come from? Has changed several times over the last thirty years, And it's changed because we keep finding fossils that totally rewrite what we think we know. So I'm going to take you back starting in the nineteen nineties.
So you know, if we were to go back, let's say to nineteen ninety, right, and if you would ask me where the feathers come from, I would have told you, well, that's easy. Birds evolved feathers. Feathers are a feature that are unique to birds.
Why do you think that is?
Because before the nineties, you know, they were the only modern animals for which we had feathers. We hadn't discovered any fossils at that point that preserved feathers.
And so the idea is that when birds evolved, part of what made them birds was that they developed feathers exactly.
We thought that feathers were one of the defining characteristics of birds. And I mean, there's other features that define birds, having a really enlarge, exaggerated sternum, to have big, huge chest muscles for powering flight. Birds have special little bones in the shoulder girdle, they have special shape of their clavical These were all thought to be defining characteristics of birds, and feathers were thought to be one of those features.
We simply hadn't found any fossils that had evidence of feathers.
So before the nineteen nineties, we just thought feathers were a birth thing. Modern birds were the only animals we had ever seen with feathers, so we thought birds were the ones that evolved them. That basically feathers started with birds, which was a totally reasonable thing to assume. But then something happened in the mid nineteen nineties.
But then in the mid nineteen nineties, the world was literally turned up side down with the dramatic discovery that some dinosaurs also had feathers.
Yes, the nineties didn't just give us grunch rock. The nineties gave us one of the most significant dinosaur discoveries in history. We're gonna talk about this discovery and how it and other discoveries changed when we think feathers evolved. Stay with us. We'll be right back, and we're back Okay. Before the nineteen nineties, we thought feathers were just a bird thing, and the story everyone agreed to was that
birds were the ones that evolved feathers. But then in the mid nineteen nineties there was a discovery that rocked everything we thought was true.
So in the nineteen nineties there was the discovery of dinosaurs preserved soft tissues from the early Cretaceous je Hall biota of China, and the Jehall biota is now recognized as one of the most important fossil localities in the world. So these fossils are found in northeast China, and they preserve lots of different types of animals, with everything from plants, insects, turtles, some early mammals, and lots of dinosaurs. What was discovered
was a dinosaur called sinosrouptrics. So Sinus ruptrics is a small little therapod dinosaur and it's only about thirty centimeters tall, and it preserves dark organic matter, dark remains of its soft tissues around the head, down the back of the neck,
along the body, and along the tail. And when the Chinese research team looked at these fossils under the microscope, they could say that that brown material it actually had structure, and that structure was that it was posed of thousands of tiny filaments, and the Chinese team surmised that these filaments were in fact a very simple sort of feather.
Basically, researchers in China discovered a dinosaur with feathers. It's a tiny dinosaur, only about a foot tall, and what the fossil showed was that it had kind of a mohawk running down its back and a fuzzy tail with stripes that looks sort of like the tail of a raccoon. Now, I know what you're thinking, that doesn't quite sound like feathers, and that's why this fossil was a little controversial.
Now this proved massively controversial because you know, the feathers that were all very familiar with, they have that clear pattern of branching. They have the central shaft and the lateral branches. But what not many people know is that some birds do have feathers that have a very simple structure. So some birds have feathers that are just simple filaments that don't have any branching. So turkeys, for instance, they have these weird, little spiky feathers that grow out of
their chin and they are bristles. They are just a simple filament. And there's a bird called the black coucal, and the black coucal the juveniles they have feathers that don't branch. So there are modern examples of these sorts of feathers, and so the Chinese team said, these are so simple in structure, it's possible that these dinosaurs are showing us some of the very earliest types of feathers.
Okay, so this wasn't a clear slam dug that dinosaurs said feathers. People thought, well, they could be hairs. Well, how do we know this are not just hairs.
Yeah, so that's a very good question, and to be honest, that question wasn't answered for quite some time because really, if you want to prove that they're not hairs, you need to prove that they're hollow and not solid. So for a long time those structures were really controversial because the Chinese teams they weren't doing the sort of microscopic analyzes that were necessary to prove that they were feathers. And what was really exciting was when the dinosaur Microraptor
was discovered. So this is a feathered dinosaur that preserves structures that are onlyquivocally feathers. You can't argue with them because they have the shaft, they have the lateral branches, and they even have the branches on the branches. They have the barbs and the barbules, and so those are effectively modern type feathers. They're identical to the feathers that
we see in modern birds. So once Microraptor was discovered, when then there was no disputing the fact that at least some dinosaurs had true modern type feathers.
All right, here's a little bit of context. We've known for a while that birds evolved from dinosaurs. If you've heard of archaep terics, if also the kind of looks halfway between a dinosaur and a bird that was discovered in eighteen sixty one. What the discoveries in China did was pushed the origin of feathers back to before archaep terics and into the kind of dinosaurs that directly evolved into birds. These dinosaurs are called therapods. So after these discoveries,
people thought, wow, feathers didn't start with birds. They started right before birds, in the dinosaurs that evolved into birds.
So then you know our concept of rock feathers were and where they came from. We felt, well, maybe feathers are something that evolved in birds and they're very close dinosaur relatives, that they were something that evolved just in the bird like dinosaurs the therapods, and that's what we thought for pretty much twenty years.
So for twenty years that was the story. Did dinosaurs of feathers? The answer was yes, a few dinosaurs, the ones that directly evolved into birds, had them, and that's when feathers started, but then that all changed in twenty thirteen.
But then in twenty thirteen, we discovered a completely different type of dinosaur that's not related to the birds like dinosaurs at all, and each had feathers.
Okay, let's get to the big twenty thirteen discovery. What doctor McNamara and her colleagues found was another dinosaur with feathers, but this one was different.
It's an Ornithiskian dinosaur, so in the same family as viserah Thops and ankylosaurs, you know, these big, lumbering kind of beasts. So we found a quart repeated dinosaur, a herbivore. Each had feathers, and it didn't just have one type of feathers, it had three types of feathers, So that really rocked the world.
What they found was a dinosaur they called Colinda dromuse, and it had hair like feathers on its head, chests, and legs. And what's significant about this dinosaur is that it's on a totally different branch of dinosaurs than the dinosaurs that evolved into birds. This one is more related to Triceratops, which is the big four legged dinosaur with the three horns, and this means feathers were even older than people.
Thought by finding feathers in a more primitive dinosaur. If these two groups of dinosaurs had them, well, that kind of implies that the genetic machinery for making feathers may have actually evolved very early during dinosaur evolution, so that these distantly related types of dinosaurs had the ability to produce feathers.
What doctor McNamara is saying is that the fact two distant dinosaur cousins had feathers implies that their ancestor also had feathers. It's sort of like if you and your cousin have the same gene, the gene probably didn't start with you. You both probably got it from your common grandmother or grandfather. This meant that feathers didn't start with the dinosaurs that became birds. They go back even further.
There is also the option that maybe two groups of dinosaurs evolved feathers independently, but we actually considered it much more likely that this shared possession of feathers reflects common ancestry, that they were present in the common ancestor. So that was the stage of play for about six or seven years.
That's right. That story only lasted about six years. And that's because in twenty nineteen, doctor McNamara and her colleagues found another fossil that totally threw that story out the window. When we come back, we'll talk about that discovery and we'll hear from our experts why scientists thinks evolved. Stay with us, you're listening to science stuff. Welcome back, all right. We're telling the story of what we know about dinosaurs
and feathers. In twenty thirteen, palontologist doctor Maria McNamara was part of a team that made a remarkable discovery. The fund feathers is a distant cousin of the dinosaurs that eventually evolved into birds. And this meant that feathers didn't evolve with birds, nor did they evolve with the dinosaurs that became birds. Other dinosaurs had them, which meant the origin of feathers went back even further. But how far back,
which dinosaur ancestor was it that first evolved feathers. The answer, it turned out, was even more surprising than anyone expected.
That was the stage of play for about six seven years, and then in twenty nineteen we discovered feathers in a completely different group of animal. We discovered feathers in pterosaurs.
That's right, Doctor McNamara and her colleagues found feathers in animals that aren't even dinosaurs. They found feathers in pterosaurs. Now, what are pterosaurs.
These are the giant flying reptiles, the cousins of dinosaurs that roamed the skies during much of the Mesozoic. So we found these little baby pterosaurs, these two juveniles from China that literally had feathers covering their entire bodies, and
they had four different types of feathers. They had some simple hair like feathers that we have found on lots of dinosaurs and that are also present in modern birds, and three types of branched feather feathers that branch at the base, feathers that branch and shaffway along the shaft, and even some feathers that branch at the tip. So we find these in these juvenile terosaurs.
So they found feathers, real feathers in animals that are not dinosaurs. They're more like the cousins the whole group of dinosaurs. Now what does this mean, Well, there are two possibilities. Either pterosaurs, the flying cousins of dinosaurs, also evolved feathers, and the feathers look the same by sheer coincidents, or feathers evolved way in the past before these two groups of animals branched off. Now, the first possibility that both groups of animals involved feathers and they look the
same by sheer coincidents does sometimes happen in nature. It's called convergent evolution. For example, birds evolved wings, but so that bats and sharks evolved fins and a streamlined body, but so that whales. But in the case of feathers, paleontologists argue this is very unlike likely. Here's how doctor Jingme O'Connor explains it.
The one of the ways that paleontology makes hypotheses is based on the principle of parsimony.
Okay, parsimony in general means being economical or cheap, but in the context of science, it means that if you have two possibilities, usually the one that's right is the simpler one. If you've heard of Alkham's razor, it's pretty much the same thing.
It's basically assuming that instead of evolution evolving these feathers in pterosaurs and then also evolving them a different time in dinosaurs. Since these groups are so closely related, it would be most parsimonious that the common ancestor of these two groups already had these features. And the reason it's present in pterosaurs and dinosaurs is because they both inherited it.
What doctor O'Connor is saying is that it would be a stretch for both dinosaurs and pterosaurs to evolve feathers independently out of the blue, especially because a the two groups of animals are closely related, so it's not a stretch to imagine their common ancestor had feathers, and b Feathers are complex, They're not easy to just suddenly evolve.
Feathers are complex structures, complex poratinous outgrowths. So the more complex the structure is, like, the more unlikely it is to evolve, you know, rather than having these complex like caoratinous external structures evolving a bunch of different times and all these dinosaurs and also in pterosaurs, it makes more sense, or it's more parsimonious for it to evolve once in the common ancestor.
And if you assume feathers evolved in a distant ancestor of dinosaurs and pterosaurs, it means that feathers evolved before dinosaurs existed.
We favor the idea that the presence of feather is in terosaurs and dinosaurs. We feel that this implies that the genetic networks required to grow feathers must have evolved in the common ancestor of pterosaurs and dinosaurs, and that common ancestor we predicted would have lived seventeen million years earlier than both.
And this leads to the shocking answer I promised. If feathers evolved before dinosaurs became their own branch of animals, it means the ancestor of all dinosaurs had feathers, which means all dinosaurs had feathers. It's not that a few dinosaurs and feathers, or that some dinosaurs had them. They all had feathers, or at least they all had the genes the ability to grow feathers. We'll get to what that means in a minute, but first it turns out that's not the end of the story.
And that was the accepted state of play for the last few years and most of the community. You know, we're happy with the evidence that we put forward that these structures were feathers, because we had evidence from microscopic analyzes. We had evidence from chemical analyzes that they basically contained the same sorts of pigment granules as feathers, and they contained you know that we had chemical evidence for the kerot and protein. But this year we produced really a quite shocking discovery.
What another shocking discovery.
We were looking in some early Triassic rocks. We were looking at animals that really they are very distant relatives of dinosaurs and pterosaurs, and we found that some of these very early Triassic reptiles, they preserve this remarkable structure on their back that's made of these materials which look
so similar to feathers. They contained the same pigment granules as feathers, but they lacked branching, so they don't fit our kind of conventional idea of what a feather is, So to be very conservative, we probably shouldn't call them feathers. They do tell us that there were animals living in the early Triassic that had structures that might have had many of the same functions as feathers.
So just this year, in twenty twenty five, doctor McNamara and her colleagues discovered proto feathers or prefeathers in an animal that lived way before dinosaurs, which means it wasn't just the ancestor of dinosaurs that had feathers, go even further back. How far back scientists don't know. So here's
the working hypothesis. Feathers, or the genetic mutation that allows an animal to grow these complex proteins into a structure on their skin, evolved long before dinosaurs, and we see feathers today in birds which descended from dinosaurs, which means all dinosaurs probably had those genes. But does that mean that t Rex or every dinosaur basically looked like a
giant chicken. Not really. Palatologists think all dinosaurs had the capacity to grow feathers, but some didn't use it red least once they got big, they didn't need it, which brings us to the reason feathers might have evolved in the first place, staying worn.
So it's very likely that large dinosaurs, if not completely lost their feathering, like highly reduced it. And so that's why I brought up the analogy with the elephant. I mean, elephant is like a big mammal, so it has to get rid of body heat. It also lives in a really hot place, but it hasn't completely lost its fur.
It still has it.
It's just very sparse. So that's why I'm just making the argument that maybe big dinosaurs would have highly reduced their feathering, but would they completely lose it?
I don't know.
Like, I can't think of any mammal that has completely lost its hair except for aquatic ones. I don't know if like we have had some hair somewhere, whales or hair, that'd be so funny.
I guess maybe a question is, what's the evolution of those from proto feathers to the feathers we see, like the beautiful feathers we see birds today. What was that progression?
So I just want to give a disclaimer that the progression from proto feather to complex fractal feather, which we call prenaceous feathers, it's highly hypothetical.
Gosh, we could spend a whole other episode just in this, but here is the working hypothesis. Feathers likely evolved to keep small animals warm, sort of like fur. You can find this in animals dating bag to be four dinosaurs. But then two things happened. Some dinosaurs started getting big, and so they stopped needing this coat to stay warm, which is why you only see baby pterosaurs covered in feathers and why paleontologists think maybe baby t rexes had feathers,
but big adult ones didn't. They probably shed a lot of it off, so no giant t rex chickens probably And also evolution figured out feathers were also good for other things.
So exactation is the fancy evolutionary biology word for evolution taking a feature that has evolved for some other reason and then hijacking it for another function. So sinoserapter its fuzzy little dinosaur covered in proto feathers, but tail is striped. These feathers are not just being used for thermal regulation. They're also being co opted for communication, either within a species like hey you know wag my tail. Hey you're
also sinoserapteris what's up? Or Hey, this is my territory, go away, you know, like just some kind of display, some kind of communication. We really can't say.
So that's why you see some dinosaurs with the fancy complex feathers. They used it for mating or to intimidate other dinosaurs, and then eventually the di dinosaurs that would evolve in the words figured out, hey, these feathers are also pretty good for flying.
So for example, feathers like the fancy, panacious feathers, they evolve for some other purpose and we're exacted for flight.
Like I said, we could go on a whole tangent about feathers. But to recap the main question of the episode, did dinosaurs have feathers? The answer is yes, they all did, and this is something we just recently found out. Does that mean all dinosaurs looked like giant chickens? Not necessarily, but it definitely means they're a lot fuzzier than we thought before. All Right, close the episode, here's doctor McNamara.
So that's where we are. It opens up all sorts of ideas about where did feathers evolve? You know, are we going to find true feathers in the early Triassic? If that's the question we're asking, Well, these new fossils from the Triassic tell us that in order to find the answers for feather origins, we need to look back in even all the rocks before the Triassic, And to be honest, that's somewhere where we never thought we were going to have to go.
That is amazing. Last question I guess is what gets you excited about finding the origin of feathers.
Because they are just one of the most complex tissue structures that vertebrates have, and because there's so much kind of required to produce them. I just really want to know why did vertebrates start producing these, Why did they give us an advantage? Why did they give our deep deep ancestors an advantage. I'm just really intrigued by it. What really was driving evolution once we come on to land, What do we do in this new environment? What are
the major challenges? You know, these are just really big evolutionary questions, and we have the opportunity with feathers actually to address some of that. So I just think it's really fun.
That's so wonderful. Well, I hope you do get a Nobel Prize for the Professor McNamara, or at the very least, I hope you get a feather in your cap.
Thank you, Thank you very much.
All right, Hey, be sure to check out my latest book, Oliver's Great Big Universe Evolution Changes Everything. Look for it in your favorite online or local bookstore, or go to Great Big Universe dot Net to learn more. Thanks a lot, See you next time you've been Listening to Science Stuff production of iHeartRadio Britten and produced by me Or Hitcham, edited by Rose Seguda, executive producer Jerry Rowland, and audio engineer and mixer Kasey Peckram. You can follow me on
social media. Just search for PhD Comics and the name of your favorite platform. Be sure to subscribe to sign Stuff on the iHeartRadio app, Apple Podcasts, or wherever you get your podcasts, and please tell your friends we'll be back next Wednesday with another episode. Hey, if you're wondering how feathers can survive the fossilization process, here's our first ever appendix with doctor Magnamara's explanation. How do these feathers
get preserved as fossils? I thought only like bones got preserved as fossils.
So yeah, ninety nine times out of one hundred, you're right. And usually when animals die, bones are the only things that end up getting preserved. But sometimes the soft tissues of animals and plants they don't rot away completely. In the case of feathers, they're made of those proteins. They're pretty tough, they're pretty robust, and they actually undergo transformations when the rocks are buried and the molecules start to
link together. They form large polymers, and it turns out that it's really hard for bacteria to destroy those polymers, so once they start to polymerize, it actually enhances their preservation potential.
So some of these proteins actually survived the fossilization products like you can see them in the rock.
We can actually track the three dimensional architecture of the protein. That's what's really distinctive about feather proteins is that three dimensional corrugated shape rather than the helical shape. So we know for a fact that some of the earliest birds and feather dinosaurs their feathers were made of the same proteins as the feathers of modern birds.