The Science of Birds - The Evolution of Feathers

Episode Date: August 1, 2024

This is Episode 101. Today, we trace the origins of feathers back millions of years, exploring how they evolved from simple filaments to the complex structures we see in modern birds. We delve into the discovery of feathered dinosaurs like Archaeopteryx and the numerous fossil finds in northeastern China during the 1990s. These discoveries revealed that many non-avian dinosaurs sported feathers of various types and complexities, indicating that feathers were not unique to birds but were a common feature among many dinosaur lineages. The evolutionary journey of feathers showcases their initial roles in insulation, display, and possibly tactile sensation, long before they were adapted for flight.Join me as we walk through the Five-Stage Model of feather evolution, which parallels feather development in modern birds. This episode is a deep dive into the intricate and mesmerizing story of how feathers came to be.~~ Leave me a review using Podchaser ~~Link to this episode on the Science of Birds website Support the show

In the summer of 2015, Dr. Lita Singh, a Chinese paleontologist from the China University of Geosciences, went to Myanmar to look for fossils, specifically animal fossils trapped in amber. There's a big market for amber in Myanmar. The rich deposits there date to about 100 million years ago. Amber is mined and sold in local markets, and a lot of it ends up as jewelry. Dr. Xing was perusing one of these markets one day when he came across a small chunk of amber that seemed to have something unusual inside. To the untrained eye, the fuzzy thing suspended in the amber might look like a fossilized piece of a fern or other type of plant. But Dr. Xing has a trained eye. He recognized that the amber actually contained fossilized feathers. After careful analysis back at the lab, Dr. Xing discovered that the feathers are attached to a tiny tail. There are at least

eight tail vertebrae. But this isn't the tail of a bird. It belongs to a young sealosaur, a type of small theropod dinosaur. It lived about 99 million years ago. This was a super exciting, groundbreaking discovery because it provided the first direct evidence of feathers attached to a dinosaur tail preserved in amber. There are many other fossils of dinosaurs with feathers, but in those fossils, evidence of feathers is left behind mostly as impressions in stone. In this chunk of amber that Dr. Xing discovered,

we can actually see the feathers themselves frozen in time inside the glass-like substance. The feathers are primitive, each with a loose structure somewhere between a down feather and a contour feather. They were more for insulation or display rather than for flight. This amazing discovery in 2015 added significant insight into the evolution of feathers and their early functions in dinosaurs.

Dr. Xing and his colleagues nicknamed the fossilized specimen Eva. Poor little Eva, this tiny juvenile dinosaur got its tail stuck in some sticky tree sap. I'd like to think that Eva survived the ordeal, and got away. It lost its tail, yes, but it ended up living a long and happy life. At family gatherings, I imagined Eva entertaining its children and grandchildren by telling them the harrowing tale of how it lost its tail. Little did Eva know that 99 million years later, its fossilized tail would cause a bunch of human scientists to get really excited. This is kind of like in the Terminator movies, right? When scientists find the severed roevales,

robot arm from Arnold Schwarzenegger's original T-800. I'll be back. Then the scientists reverse engineer the technology from that arm to eventually create the artificial intelligence called SkyNet that turns evil and tries to wipe out humanity. So let that be a cautionary tale. We should probably be careful with that tiny dinosaur tail trapped in amber, lest it fall into the wrong hands.

Hello and welcome. This is the Science of Birds. I am your host, Ivan Philipson. The Science of Birds podcast is a lighthearted exploration of bird biology for lifelong learners. This is episode 101, and today we're talking about the evolution of feathers. We used to think that feathers were a feature unique to birds. And that's definitely true if we're talking about the modern world. Among all living animals, only birds have feathers. And they've been the only feathered creatures for the last 66 million years or so.

But if we go back further in time, before the big extinction event that happened 66 million years ago, the story gets more interesting. And that's what we're going to do. do in this episode. We'll explore the humble origins of feathers, their early form and function, and how they eventually became the elaborate structures that allow birds to fly. I've published two other podcast episodes about feathers. Episode 13 focused on the structure and function of feathers, and episode 56 was all about feather colors. To get the most out of this episode, I recommend listening to at least episode 13, so you'll have a good understanding of feather structure. But as a quick review, a typical contour feather consists of three main parts.

There's the calamus, which is the hollow base anchoring the feather to the bird's skin. Then there's the rachis, which is the central shaft extending from the calumus, and which supports the feather's other structures. And then we have the vein, which is the flattened, flexible surface on either side of the rakeas composed of interlocking barbs and barbules, creating a smooth aerodynamic surface. Barbs are like little branches that spread out from either side of the rakus, the central shaft. Barbules are much smaller. They're like twigs that grow off of each barb. In the contour feathers of modern birds, barbules have tiny hooks that latch on to other barbules.

This works sort of like a zipper or like Velcro to secure the furrow to secure the furthers. the barbs together, making the vein more rigid. And remember that feathers are not alive. They grow out of the skin from living cells, but the things we eventually see as bird feathers are dead structures. They're made of waxy, sort of plastic-y proteins called keratins. Human hair and fingernails are also dead structures made of keratins. Okay, so hopefully all of that makes sense. Let's go ahead now and take a magical journey into the deep past to learn how feathers came to exist. Feathers don't generally make great fossils. They're relatively delicate, and keratin decays much faster than mineralized tissues like bone and teeth.

The preservation of feathers requires very specific and rare connections. conditions, such as a sudden burial in fine-grained sediments like silt or ash, which can protect and preserve delicate structures. So fossil feathers are rare. It took us humans kind of a long time before we discovered one. But in 1861, a beautifully preserved specimen was found in a limestone quarry in Germany. It was a single feather. It came from an animal that lived during the Jurassic period, about 150 million years ago. And that animal was Archaeopteryx. Before long, several other Archaeopteryx fossils were discovered that included not just a feather, but all or most of the body, the skull, limbs, tail, and heaps of feathers. These world-famous

fossils show us a creature with long feathers on its arms, on its tail, and even on its legs. Despite Despite having broad wings with feathers, and at least the potential to fly, Archaeopteryx had more similarities with other small dinosaurs of the Mesozoic era than with modern birds. We're talking sharp-toothed jaws, three-fingered claws, and a long bony tail. The discovery of these fossils was a big deal. Scientists in the mid-1800s were kind of losing their minds. Studying the fossils, they saw what looked a lot like a little dinosaur, but a little dinosaur covered in elaborate feathers.

And it's got wings! Archaeopteryx lived 150 million years ago, so that means the origin of feathers had to be before that time, right? Almost certainly millions of years before. Some paleontologists today argue that Archaeopteryx is not the direct ancestor of modern birds. It's a close cousin, they say.

In any case, there's evidence that, the true direct ancestors of all birds were indeed flapping around at about the same time, 150 million years ago. But most scientists in the 1800s thought of Archaeopteryx as a kind of primitive bird. Fair enough, I guess. And so for about 120 years, the world thought that the first feathers had evolved as features unique to the first birds. But fast forward to the 1990s, And things start to get crazy. Everybody was watching Seinfeld and collecting beanie babies. We were all chugging Crystal Pepsi and listening to Nirvana and a tribe called Quest on CD with headphones that had a chord.

But another thing that happened in the 90s was that thousands of fossil birds and other dinosaurs started to be unearthed in northeastern China. Many of these fossils revealed the beautifully preserved anatomy of animals that lived in the early Cretaceousy. period, about 122 million years ago. Notably, many of these fossils show feathers in intricate detail. And here's the thing. A bunch of these feathered creatures were not birds. They were non-avian dinosaurs. Unlike archaeopteryx, some of these non-avian dynos were not close cousins of birds. Some were way too big to ever fly, and yet they had long, elaborate feathers festooning their arms and tails. Among all these fossils from China, scientists have identified every kind of feather we see on the bodies of living birds. Bristles, fluffy down, short contour feathers on the

body and long, stiff, panaceous feathers. But some critters living during the early Cretaceous sported other types of feathers that we don't see on any birds today. For example, there were these strange ribbon-like feathers waving around on the tails of some small dinosaurs. It seems that many kinds of dinosaurs, both avian and non-avian, were sort of experimenting with different types of feathers and putting them to use for a variety of functions. And there were also multiple independent dinosaur lineages experimenting with flight. The discovery of all these fossils in the 1990s kicked off a scientific revolution. The fossils have taught us several major things.

1. The origin of feathers predates the origin of birds. 2. Elaborate contour feathers with a stiff, flat vein evolved before flight, for some function other than flight. And 3. Because so many non-avian dinos had feathers, these structures must have first evolved way earlier than 150 million years ago. because I should mention that scientists have now discovered feathers of one kind or another in species scattered all across the dinosaur tree of life. All dinosaurs belong to a single evolutionary lineage called Dinosauria. Taxonomically, Dinosauria is a super order.

Within this lineage, there are two major branches, or orders. Sariscia and Ornethyskia. Sariscia includes theropods like Tyrannosaurus rex as well as soropods like the enormous brachiosaurus. The order Ornethyskia includes some familiar species like Stegosaurus and Triceratops. Well, feathers have been found here and there on species from both orders, from both Soryskia and Ornethyskia. This means that feathers were, most likely, present in the common ancestor of all dinosaurs. That creature is believed to have lived

during the late Triassic period around 230 to 240 million years ago. That pushes the origin date for feathers back almost 100 million years because when all we had was archaeopteryx fossils to go on, the origin date was quote unquote sometime before 150 million years ago.

Now if you're imagining fancy plumes like what we see on modern birds or even on archaeopteryx, that's not quite what I'm talking about. Yes, as I've mentioned, there were structurally complex feathers adorning the bodies of some non-avian dinosaurs. However, what we find more frequently among the more distant Sariscian and Ornithiscian relatives of birds are simple feathers. These are more hair-like. They're bristles, or some are what scientists call monophilaments. Other dinosaurs, like some close relatives of Tyrannosaurus Rex, had fuzzy down-like feathers. The semi-official name for this hair-like skin adornment is dino-fuzz. For example, a theropod cousin of T-Rex is U-Tyrannis, Huali, a 30-foot-long

carnivorous dinosaur from the early Cretaceous period. It lived in what is now northeastern China, in a temperate rainforest environment. Fossil evidence shows that eutiranus had a body covered with filamentous feathers. In other words, dino fuzz. Or maybe more like dino shag in this case, because the feathers were about eight inches or 20 centimeters long. This shaggy coat of feathers is thought to have provided insulation, which is particularly interesting given Eutiranus's large size.

So feathers, mostly simple hair-like ones, were a common feature among many dinosaurs. These were almost certainly present in the single common ancestor of all dinosaurs that lived between 230 and 240 million years ago. The dynos that don't seem to have feathers at all include some familiar beasts like Stegosaurus, Ankylosaurus, Iguanodon, and all of the sauropods. within the latter group are the largest land animals that ever lived. All of these seemingly featherless dinosaurs probably ended up that way secondarily. In other words, they descended from ancestors that had feathers,

but along the way the feathers were lost. They were no longer needed. If the primary function of those primitive filamentous feathers in the earliest dinosaurs was to keep the body warm, that might explain their loss in the gargantial. dinosaurs that came later. Because larger animals have a lower surface area to volume ratio compared to smaller animals. This means they lose heat more slowly and retain body heat more effectively. As a result, it could be that large dinosaurs like sauropods would not need additional insulation from feathers

to maintain their body temperatures. This is kind of like how elephants are mammals, but their gigantic bodies have very few hairs on them. Now, there's an entirely different group of critters I want to talk about for a moment. You probably know that all of those flying reptiles flapping around in the Mesozoic using bat-like wings, the pterodactyls or terosaurs, are not dinosaurs. They belong to their own taxonomic order. Just as crocodiles are not dinosaurs, terrosaurs are not dinosaurs. Well, it turns out that most pterosaurs had their own fuzzy covering, their own hair-like structures.

These have the technical name picnofibers. That first part, picno is spelled P-Y-C-N-O. So the question is, are picno fibers the same thing as feathers? Did pterosaurs inherit their fuzzy fibers from the same ancestor that gave dinosaurs their fuzzy fibers? If the answer to that question is yes, as some scientists argue, that would push back the origin of feathers even further, as far back as 250 million years ago. However, the homology, in other words the shared ancestry

of picnophibers in pterosaurs and feathers in dinosaurs is a hotly debated topic. There are compelling arguments for both shared ancestry and the possibility of convergent evolution in the two groups of animals. But we need more evidence before we'll know the full story. Now, in case you're wondering, even though I keep saying the earliest feathers were hair-like, they were fundamentally different from mammal hair.

So dinosaurs did not inherit feathers from their common ancestor with mammals. That creature lived around 300 million years ago. Feathers and mammal hair evolved independently much later. So looking at the entire branching tree of dinosaur diversity, we see a rough progression, a progression of increasing feather complexity. Simple bristles evolved in the most ancient dinosaur lineages. Bristles evolved into tuft or down-like feathers. Later we get feathers with a central shaft and barbs.

Then come symmetrically veined feathers. And finally, there are asymmetrically veined feathers, like the flight feathers of modern bird. So far, we've been talking about evidence from fossils. There's a progression of increasing feather complexity through time, as shown by the fossil record. But there are other ways that scientists have investigated the evolution of feathers. It's possible to look at the biology of living birds. and other animals to understand where feathers came from. All vertebrates have some sort of cutaneous appendages,

little bits of bling bristling on the surface of their skin. Sharks have dermal denticles, fish have bony scales, reptiles like snakes and lizards have scales made of keratin, mammals have hair, and dinosaurs have feathers. Before the Dino Revolution of the 1990s, the leading hypothesis was that feathers originally evolved from the scales of reptiles. As in, there was some ancient lizard-like creature covered in scales, and its ancestors developed longer and more elaborate scales over millions of years,

and then, ta-da, feathers. Now, there are some similarities between reptile scales and feathers. Both are made of proteins called beta-carotins, also called corny, beta proteins. These are the toughest natural polymers in the world, and today they're found only in the cutaneous appendages of birds and reptiles. However, research in the last couple of decades has led us to abandon the idea that feathers evolved from reptile scales. A lot of this groundbreaking research comes from the field of evolutionary developmental biology, known as Evo-Devo for short. Not to be confused with,

With Devo, the new wave band from Akron, Ohio. EvoDevo provides a framework for understanding how complex structures evolve through modifications of developmental pathways. And what do I mean by developmental pathways? These are like a series of instructions that guide how an organism grows and forms. The growth of an individual, a bird, let's say, involves many development. pathways, each responsible for a specific part of the development process. One pathway tells cells when and how to divide and multiply, while another instructs cells on what type of cell they should become, such as muscle cells, nerve cells, or skin cells. There's also a pathway that ensures

tissues and organs form in the right shape and location, making sure, for example, that the heart ends up in the chest, and some pathways regulate how big the organism grows and how its body parts stay in proportion. All these pathways work together, like a team of builders following different parts of a detailed construction plan to make sure the organism develops correctly. Genetic information in DNA provides the construction plan, the blueprints. Information from one step in a pathway to the next is transferred typically by molecules like proteins. If any of these developmental pathways don't work properly, it can lead to problems in growth and development. The growth of an individual is an insanely, mind-bogglingly complex process

involving many interconnected developmental pathways. And if there are any mutations in these pathways, then that can lead to interesting evolutionary changes. By looking at the pathways involved in feather growth, and at the genes involved, some scientists have been able to come up with some interesting ideas about the progression of feather evolution. That progression appears to be reflected in the way a single feather grows out of the skin of a modern bird. This process begins at the embryo stage, with tiny areas of skin called placodes, where future feathers will grow. These placodes form small bumps called feather buds, which elongate as the cells rapidly divide.

The feather bud then forms a central shaft, i.e. the rakeas, with barbs branching off the sides. As the process continues, the barbs develop barbules that hook together, creating a smooth, interlocking surface crucial for flight and weatherproofing. As the feather grows, it pushes through the skin and breaks free from its protective sheath, and it unfurls to become a fully formed feather ready for use and abuse. Over time, the feather will wear out, so birds periodically molt, shedding old feathers and growing new ones. All feathers in living birds, regardless of their complexity, develop from a simple tubular structure that projects from a follicle.

And a single follicle on a bird can make multiple feather types over the life of that bird. And these things were probably true for all of those. feathered dinosaurs as well. The developmental pathway of a feather that I just breezed through with you aligns reasonably well with the fossil evidence from early feathered dinosaurs, reinforcing the idea that feathers evolved in stages, with increasing complexity through time. I want to insert a side note here. Earlier, I pointed out that feathers did not evolve from the scales of reptiles. That hypothesis has been disproven. But maybe you're a smart cookie and you're thinking, well, what about all those scales on the legs and feet of birds?

Bird legs look a lot like the legs of a dinosaur or a lizard. That seems to suggest that birds used to be all scaly, then the scales on their bodies eventually evolved into feathers. That, my friend, would be a reasonable interpretation. And that's what I used to think, not that long ago. But let's return to the idea of developmental pathways to see what's really going on. Yes, most birds lack feathers on their legs, but not all. Remember that many owls and raptors have feathered legs, and tarmigans have densely feathered legs and feet.

Scientists have figured out that the default mode on the skin of birds is to produce feathers, like everywhere, including on the legs and feet. Only when a pathway called S-H-H is inhibited in a part of the skin, do scales grow. If certain genes don't get expressed, you get scales. So the scales on bird legs and feet are actually modified feathers. They have a very different development from the development of scales on the skin of a snake or a lizard. Although they look similar to us, these structures are not the same thing. Naked legs on birds is a relatively recent thing in the evolutionary sense.

Most of the feathered dinosaurs of the Mesozoic, both avian and non-avian, seem to have had sexy feathers running down the length of their legs. And you've probably seen that some chicken and domestic pigeon breeds have feathers on their legs and feet. That's because those breeds have a mutation or two in the S-H-H-developmental pathway. And you know what S-H-H stands for? Sonic Hedgehog. For real, I'm not joking.

The S-H-H-H-H-H-H-H-H-H-HGIN makes a protein that scientists named Sonic Hedgehog. Not Sonic the Hedgehog, just Sonic Hedgehog. Why? Well, it's a long story. And we ain't got time for that. Because it's time for us to walk through the five stages of feather evolution. The eight planets of the solar system, the four horsemen of the apocalypse, the seven-layer burrito, and, just as important, the five-stage model of feather evolution.

This model was proposed by Dr. Richard Prum, currently a professor of ornithology at Yale University. Each stage in the model represents an evolutionary novelty, some new growth mechanism or developmental pathway that caused a big change in the structure of the feather. This whole thing is based on feather development. The idea being that the way a feather grows on living birds probably parallels the stages of feather evolution. Sort of like how human embryos go through stages

with features like gills, fins, and a tail, echoing parts of our evolutionary history. And even as an adult, I still sort of look like a Neanderthal. So maybe that echoes something about my own evolutionary history. All right, you ready for the five stages of feather evolution? No? Too bad. Here we go. Stage one. feathers began as simple unbranched filaments similar to hairs this type of feather shows up all over the dinosaur tree of life and many living birds have some feathers like this on their bodies

complexity is only going to increase with each stage here stage two the filaments sometimes called protofeathers evolved into a tuft of filament emanating from a single base, resembling a brush. This is vaguely like the down feathers of modern birds. Stage three. Filaments evolved into unbranched barbs radiating from the rakeas, the central shaft. And by unbranched, I mean the barbs don't yet have barbules on them. But by the end of stage three, barbules have evolved.

Stage three has some intermediate stages. The one called Stage 3A plus B is beautifully reflected by what we saw in Eva, the little dinosaur that got its tail stuck in tree sap 99 million years ago. Eva's tail feathers had barbules, but these were undifferentiated, or naked barbules. In other words, they didn't have any tiny hooklets on them. Eva's feathers show a very slender, weakly defined central shaft, and the barbs branch out from either side of the shaft in an alternating arrangement. Eva's fossil feathers give us some evidence that barbules may have evolved before a true rakeus.

Stage four. In this stage, we get a feather with a closed vein. Now it looks like a feather feather. You know what I mean? Hooklets on the barbules appear, and they zip the barbs together. It's not so easy for wind to pass through a feather like this. The feather at this stage is symmetrical. The veins on either side of the rakeas are about the same shape and size.

Stage five. The final stage involves the development of asymmetrical flight feathers. This asymmetry gives the feather aerodynamic qualities that are needed for flight. The flight feathers of living birds are asymmetrical. One vein is larger than the other. This entire evolutionary process, from stage one to stage five, may have taken almost 100 million years. Prum's five-stage model is supported by fossil data and developmental data. But it's still a theory, a framework for thinking about feather evolution.

It's possible that the real way it all went down was more complex. Right? Because that's a recurring theme here. on the Science of Birds podcast. Things in nature that we think we have all sorted out often reveal themselves to be much more complicated when we take a closer look. It's like gulls. As a newbie birder, you might look at some gulls on a beach

and think, okay, looks like we've got some seagulls here. They look pretty much all the same, so there's probably just one species. Cool, I've got this. But then, when you get more experience, When you learn to stop calling them seagulls, and you peruse the gull section of your field guide, you realize, uh-oh, it turns out this ain't no walk on the beach. What's the deal, gulls? Why do you guys got to be so hard to identify?

I hope that by now you've got a sense of when and how. how feathers evolved. But we haven't talked about the why very much. Why did feathers evolve? What was their original function? Well, one thing we can say with confidence is that the first feathers did not evolve for flight. That came way, way later. One of the leading hypotheses for the earliest function of feathers is that they provided insulation. Hair in mammals and feathers in dinosaurs evolved during the Triassic period, a tumultuous time following the worst extinction ever at the end of the Permian period. Maybe insulating structures like hair and hair-like filamentous feathers were helpful in a world with extremes in temperature. But some scientists

argue that for insulation to work, it would need to cover large parts of a dinosaur's body and grow as a thick coat. The earliest feathers seem to have been more sparse on the body. So these scientists propose another function for the first feathers. Tactile sensation. Modern birds possess rictal bristles, stiff feathers that can sense movements and vibrations, that enhance a bird's sense of touch. You know, like the whiskers of a kitty cat. It's possible that the first feathers appeared as tactile bristles on the face of early dinosaurs. However, I don't think there's any fossil evidence for facial bristles on triassic dinosaurs. Not yet, anyway, but this is an interesting hypothesis.

Whatever their original function, feathers eventually got repurposed for several super-important functions. They became adaptations for camouflage and for display. As I mentioned earlier, there were some non-avian dinosaurs. that were too big to fly, but they were adorned with large, panaceous feathers. This gives us evidence that large, complex feathers, corresponding to stage four of the model, evolved first before flight was a thing in dinosaurs. So what would those feathers be useful for, if not flying?

There are multiple possibilities, and display is one of them. Maybe those flightless dinosaurs flashed brightly colored arrays of, feathers on their arms and legs in the general direction of potential mates. Feathers might have been used in courtship behaviors or threat displays. And there's good reason to think those feathers were colorful and richly patterned, because we know that feathers of many dinosaurs had melanin pigments. These sometimes show up in well-preserved fossils. You may remember from the podcast episode I did on feather colors that melanin pigments

give feathers their black, brown, and gray tones. Structural colors like iridescence and shades of blue can also be achieved with melanin. However, there doesn't appear to be any fossil evidence for the other major class of feather pigments, the carotenoids. These give feathers their red, orange, yellow, and pink hues. Birds make their own melanin

in special cells called melanocytes. but carotenoids have to come from what a bird eats. Birds can't make their own carotenoids, and that may have been true for all feathered dinosaurs. In any case, the ability to incorporate carotenoid pigments into feathers seems to have evolved after the big extinction of 66 million years ago. Evidence from a study published in 2014 suggests that birds first started incorporating dietary carotenoids into their plumage in the Paleocene epoch, which was 66 to 56 million years ago.

This finding is based on an analysis of modern bird species and their evolutionary relationships. We still don't have any fossil evidence for feather carotenoids. Another finding from that 2014 study was that carotenoid-based plumage coloration appears to have evolved independently multiple times within different avian lineages over the last 66 million years. This may have happened independently in 13 different avian orders. So feathers started off as simple filaments that acted like insulation or maybe like whiskers. They became more complex throughout the Mesozoic era, eventually taking on their stage 5 form, with interlocking barbs and an asymmetrical shape. Adaptations needed for flight.

By the time our buddy Archaeopteryx came along, 150 million years ago, flight was indeed a thing, and feathers were taking on their familiar form. By the early Cretaceous, a few million years later, all the direct ancestors of birds could fly. I'll have to dedicate an entire episode to the evolution of flight. That's a big topic on its own. Natural selection acting generation after generation over many millions of years took feathers from being simple, sparse filaments to being luxurious dino shag, and eventually to being the most complex cutaneous appendages ever to grace the body of a vertebrate animal. In modern birds, feathers became ever more complex and diverse in form and function over the last 66 million years.

And natural selection is still grinding away, shaping and honing them. Evolution doesn't stop just because the podcast, episode is coming to the end. So what's next? How might feathers change as birds continually adapt to the wild, unpredictable world around them? Thanks for listening to Episode 101. I find this stuff really interesting, and I hope you do too.

I'm sure there'll be more amazing scientific discoveries about feather evolution, and I'll eventually have to update this episode. I say, bring it on! I'm very pleased to say that I got a nice wave of new supporters on Patreon since my last episode. So here's a big shout out to Stephen Giambardino, Nicole Matsusack, Frank and Angela Shumpert, Raven, Frank, Michael Carion, Martha Vandervort, Serulian Warbler, Tracy and Catherine Blue. Wow, thanks so much to all of VIII. you. If you, dear listener, are thinking about supporting this podcast and getting your own shout

out, you can check out my Patreon page at patreon.com slash science of birds. You can also shoot me an email if you have something you'd like to share with me, a thoughtful comment perhaps, or maybe you want to tell me what you were doing in the 1990s when all those feathered dinosaurs were first discovered. But were you even alive yet? Or maybe you were still in the womb? You were a developing embryo with fins and a tail. Well, in any case, my email address is Ivan at Scienceofbirds.com. You can check out the show notes for this episode on the Science of Birds website, scienceofbirds.com.

I'd like to say that I'll post photos of some feathered dinosaurs, but I guess cameras didn't exist 150 million years ago? Sorry. I'm Ivan Philipson, wishing you a wonderful day. Peace.