Archive: Feathered Dinosaurs

All dinosaurs were originally thought to be related to lizards - the word 'dinosaur' was created by Richard Owen (1804-1892) from the Greek for 'terrible lizard' - but that now appears to be false. In this archive episode, first released in October 2017, Melvyn Bragg and guests discuss the development of theories about dinosaur feathers, following discoveries of fossils which show evidence of feathers. In the last century, the discoveries of these fossils have established that at least some dinosaurs were feathered, and that some of those dinosaurs survived the great extinctions and evolved into the birds we see around us today. There are still many outstanding areas for study, such as what sorts of feathers they were, where on the body they were found, what their purpose was and which dinosaurs had them. With Mike Benton Professor of Vertebrate Palaeontology at the University of Bristol Steve Brusatte Reader and Chancellor's Fellow in Vertebrate Palaeontology at the University of Edinburgh and Maria McNamara Senior Lecturer in Geology at University College, Cork Producer: Simon Tillotson In Our Time is a BBC Studios production A world-class seminar every week. Spanning history, religion, culture, science and philosophy, In Our Time celebrates the pursuit of knowledge and the enduring power of ideas. In each episode, host Misha Glenny and expert guests explore the characters, events and discoveries that have shaped our world.

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  Hello. In the latest edition of In Our Time, my guests and I discussed the first dinosaur to ever be given a scientific name, Megalosaurus. It was formally described by the geologist William Buckland in 1824, before we actually had the word dinosaur. During the 19th century, Megalosaurus became part of a shift in how people understood the history of our planet and life on it. But over the last century, there's been another shift in what we know about dinosaurs: feathers. In this archive episode of In Our Time, Melvin and his guests unpacked the discovery of fossils, establishing that at least some dinosaurs were feathered.

• 3:13Speaker 01

  If you're anything like me, it'll completely change how you think about prehistoric life and how you look at birds today. I hope you enjoy listening.

• 3:23Speaker 05

  Hello. Until 20 years ago, dinosaurs were widely assumed to be large lumpen lizards that became extinct millions of years ago. Discoveries in China have since shown dramatically that many were fast and feathered, and some survived the great extinctions and are the ancestors of our modern birds. The recently discovered Chinese fossils of feathered dinosaurs are so well preserved, scientists can even work out the feathers' colour and where they were found on the dinosaurs' bodies, and theorise about their use for displays, insulation, and in some cases perhaps, flight. Even the large Tyrannosaurus may have had downy feathers, and it appears that the small Velociraptors had long quill-like feathers arranged on arms that looked like wings.

• 4:07Speaker 05

  With me to discuss feathered dinosaurs are Mike Benton. Mike Benton, Professor of Vertebrate Palaeontology at the University of Bristol. Steve Brusatti, Reader and Chancellor's Fellow in Vertebrate Palaeontology at the University of Edinburgh. And Maria McNamara, Senior Lecturer in Geology at University College Cork. Mike Benton, how did the idea become commonplace that dinosaurs were slow, heavy lizards?

• 4:30Speaker 01

  I think this is what many of us were brought up with. And I think those over the age of maybe 30 or 40, definitely. And we still commonly use the word dinosaur to mean a sort of failure or something that's lumbering and hopeless. So we were brought up with books that show large, grey-coloured, often reptilian creatures. And the assumption is they'd be kind of dragging their tails and crawling around in the swamps. And that fitted an idea that they're extinct and they're long forgotten, and that they'd had their day and they couldn't survive. But as you said in the introduction, that's massively changed as a result of new discoveries.

• 5:07Speaker 05

  Because they lived for... If we, the human species, lived as long as they did, we would be lucky, wouldn't we?

• 5:13Speaker 01

  Well, yes, indeed.

• 5:14Speaker 05

  Or not.

• 5:15Speaker 01

  And I think thinking of the time they were on the Earth, they clearly were massively successful. And so the new discoveries help us to understand why.

• 5:24Speaker 05

  And did it... Why did it catch on so firmly in the imagination of the general public, and particularly the younger general public? Why the largeness and the lumberiness and the sleepy slowness? Why was that? And the power of the Quaterosaurus and that? Why do you think it caught on so much?

• 5:38Speaker 01

  I think people liked the idea because it was something like a fictional world. It was something like dragons and monsters. And we all want to believe in those kinds of things. And there they were. And so you... And they were legitimised because they were real. You could go to the Natural History Museum and see these great skeletons. And I think also for the scientists, the fact that many of them, like Diplodocus and Brontosaurus, were absolutely huge. So they would have weighed maybe 50 tonnes compared to the biggest of elephants, weighing five tonnes. You have to think, how could you have an elephant of that size? Therefore, the world must have been massively different. They must have been living in a different way, maybe living in slow motion. And then kids have always loved it, of course,

• 6:23Speaker 01

  because of the imagination and sort of thinking of heroes and other worlds where they might have liked to live.

• 6:32Speaker 05

  Given the interest in Kindle once it got started, it took a long time to start. Thomas Huxley, Darwin's bulldog, he was called in the 19th century, was someone who dug into the fossil theory of that as early as anybody else around about.

• 6:48Speaker 01

  Yes, and so Huxley got it right. Around 1860, 1870, he was studying some of the early dinosaurs, particularly the two-legged ones that we generally call the meat eaters, that we generally call theropods. And he noticed, and he looked also at Archaeopteryx, which was the oldest bird and still is reckoned to be the most primitive bird. They had just been discovered in Germany. And he noticed that apart from its feathers, Archaeopteryx had the skeleton of a little dinosaur. And so he had a vision of them as a bit more active. And he was pretty clear then, so long ago, that birds and dinosaurs were close relatives.

• 7:30Speaker 05

  What material did they have to work from?

• 7:33Speaker 01

  So there wasn't a great deal at that time. There were a number of isolated large bones that had been collected in England from the 1820s onwards. No complete skeletons, really. And then I think he was very influenced by discoveries in South Germany around 1860, where they found skeletons of a small dinosaur called Compsonathus and of Archaeopteryx. And of course, there was a creature the size of a pigeon with its wings outspread with clear feathers along the wings. And yet he could see that it had a reptilian skeleton.

• 8:06Speaker 05

  How was Huxley's news received?

• 8:11Speaker 01

  Well, I think he pushed it because he was, as you said, Darwin's bulldog. He was, he very clearly saw this as evidence of evolution. Here was the sort of missing link between reptile and bird. And so he was enthusiastic, and I think a lot of others at the time. But then, very oddly, we sort of reversed for about 100 years, really from 1870 to about 1970. And it was during that time that more complete giant skeletons were coming out of the United States and Mongolia and other parts of the world. And I'm not quite sure why people stepped back from Huxley's view. Maybe it was just the sheer size and numbers of these giant dinosaurs

• 8:55Speaker 01

  that they thought, you know, the world was truly different.

• 8:59Speaker 05

  Steve Brusatti, before we go further, can you give us a few astonishing facts about the lifetime and what they did and why they were there so long? And how most of them were extinguished so quickly?

• 9:11Speaker 01

  Well, I'll try to do the story of dinosaur evolution in 30 seconds or so.

• 9:14Speaker 05

  No, you go on, don't rush. Really, don't rush. I'll wave my hands if you're going too long.

• 9:18Speaker 01

  Well, it was a long time they lived. So the first dinosaurs show up about 230 or 240 million years ago. And this is when the Earth is recovering from the worst extinction that ever happened, this extinction at the end of the Permian period, when maybe 95% of all things went extinct. So you have this new world after the extinction, open playing field. And that's when dinosaurs entered the scene, along with a lot of other groups like mammals and turtles. And so then, these first dinosaurs, they got their start slowly. They didn't take off all of a sudden. They didn't spread around the world like an infectious virus or something like that. They took their time, about 50 million years it took for them

• 9:59Speaker 01

  to slowly diversify until another extinction wiped out a lot of their early rivals. And then in the Jurassic period, dinosaurs spread around the world. You got enormous dinosaurs evolving, the big colossal long-necked dinosaurs, the bus-sized meat eaters. They were living on all continents. The continents were one at that time, Pangaea, the single landmass. But it was breaking up gradually. The dinosaurs were along for the ride, and they continued to evolve until the end of the Cretaceous period, 66 million years ago, when this six-mile-wide asteroid fell out of the sky. Things changed very quickly. The T. rexes and Triceratopses and Brontosaurus, they couldn't cope, but some birds could. And now we have birds still with us.

• 10:43Speaker 05

  We should print that out and hang it on the wall of most classrooms. Now, what are the significant divisions in the dinosaur mass?

• 10:53Speaker 01

  There's a lot of dinosaurs now. There's over 1,500 species that have been found and people are finding new ones all the time. It's really an incredible moment that we're all in right now because somewhere around the world right now, somebody's finding a new species of dinosaur, on average, about once a week. So we're getting about 50 new species a year. This is the golden age and they're coming from everywhere. China, of course, as we'll talk about, but every continent dinosaurs are found on. And we're even finding them up in Scotland. So there are so many species. There are lots of classification schemes. These are the things that a lot of young kids memorize and a lot of people like to argue about. But really, to me, the most important divisions of dinosaurs, there's

• 11:35Speaker 01

  three main groups. There's the long-necked ones like Brontosaurus. We call those the sauropod dinosaurs. There are the plant eaters with beaks. These are what we call the ornitho-phygian dinosaurs, so things like Triceratops and Stegosaurus. And then there's the theropod dinosaurs, the meat eaters.

• 11:50Speaker 05

  Is there one group in particular that the feathered dinosaurs enter into?

• 11:54Speaker 01

  It's this third group, the theropod dinosaurs. So birds come from theropod dinosaurs. They evolved from theropods the same way humans evolved from apes. So birds are theropod dinosaurs.

• 12:07Speaker 05

  And what distinguished theropod dinosaurs to make them carry the feathers?

• 12:12Speaker 01

  Well, this is the big question. And this is what we're learning so much about, you know, in China over the last couple of decades. It looks like feathers go way back to the earliest theropods. And then it looks like one group of these theropods, over time, gradually got small, changed their skeleton, evolved feathers, changed those feathers, and turned into birds. So some theropods, like T. rex, for instance, these were enormous, plotting meat eaters. Other ones had crests and sails on their backs. Some were tiny. There were lots of variety of these theropods, but birds emerged from that great diversity.

• 12:52Speaker 05

  Over 50 million years?

• 12:53Speaker 01

  Yes. It was a long process. A bird didn't just evolve one day. A T. rex didn't mutate into a chicken. That's not how evolution works. But it was a long process of gradual change. And at the end of that, a bird emerged, a small, feathered, winged, flying dinosaur.

• 13:10Speaker 05

  Maria McNamara, we're talking about feathers. What do our listeners to understand by feathers?

• 13:17Speaker 03

  Okay, so feathers are really remarkable, excuse me, integumentary structures. So they're derived from our integument or our skin. And we know that by studying the development of feathers in chick embryos, we can actually work out where they come from. So we know that during growth of a chick, that as the skin is developing, you form a little thickened region in the outermost part of your skin. This thickened region starts to project inwards, forms a follicle. And the cells lining that follicle, they're from the dermis, the lower part of the skin. They die off and they start to form the interior part of the feather.

• 13:59Speaker 03

  At the same time that this is happening, you, some cells start to project outwards from the skin to form a hollow shaft. And this is basically the fundamental structure of a feather. It's a hollow tube. But when you look at modern birds today, feathers are actually much more complex than that usually. They're actually the most complex structures derived from the skin in vertebrates, animals with backbones. So a typical feather, flight feather, in a crow or a jackdaw, it actually has several levels of branching. So that central shaft or tube, which, you know, would be familiar to readers or listeners as the quill part of the feather, that branches into smaller structures called barbs. In

• 14:44Speaker 03

  turn, those barbs have little branches called barbules. And these barbules are in turn differentiated at their tips into little hooklets that can zip together to form a nice closed vein.

• 14:56Speaker 05

  One thing that interests me, picking up from what Steve said, is that there doesn't seem to have been, inside this long range of life that the dinosaurs had, any development of, evolution of feathers. There were feathers at the beginning, there were feathers in the middle, there were feathers at the end. Is that right? Did they just pop up for a reason we, as yet, don't know?

• 15:15Speaker 03

  Okay, so when you look across the dinosaur tree, when you look across the theropods and also the ornitho-phygian dinosaurs, we can see evidence of feathers at different developmental stages, different evolutionary stages. So we see a spectrum of fossil feathers that go right from the very complex feathers that are anatomically modern, they look identical to what we have in birds today, right back to clumps of filaments, and even further back to just simple filaments that, for all, you know, intents and purposes, look like hairs.

• 15:51Speaker 05

  So there was evolution?

• 15:52Speaker 03

  Yes, we can, we can track the evolution, that what we see in the developing chick as a feather develops in an embryo, we can see these different stages of morphological development in fossils.

• 16:05Speaker 05

  Mike talked about the 100 years backward step. It was given a huge acceleration forward with the discovery of this great field of fossils, miles, kilometers of fossils, in northeast China, which seems to have changed everything in your area of study. Can you tell, listeners, how that happened?

• 16:24Speaker 03

  Okay, so in the early, mid 1990s, there came, the initial report was of a new dinosaur called Sinoceropteryx. And the discovery of this specimen absolutely electrified the world of paleontology, because this dinosaur preserved feathers. So these were very controversial, of course, because the feathers in Sinoceropteryx, they're very, very short. They're only about 10 millimeters long. And they don't really look like the complex feathers we see in modern birds. They look like simple, hair-like filaments. So the initial reports, you know, which gained huge attention among paleontologists and the media alike, because it was the first

• 17:09Speaker 03

  direct evidence for a link between birds and dinosaurs. It was the first dinosaur bearing feathers. And these were actually very controversial, because you had some paleontologists who claimed that, who reinterpreted those feathers as other structures, as just fibers from the skin.

• 17:27Speaker 05

  Can you give us some idea of the range of material available and the vast, as it were, fossil fields there are in northeast China?

• 17:35Speaker 03

  Well, I mean, you know, you have, so, most of the fossils that we're talking about, they come from two main fossil biotas. The Jehal biota, which is early Cretaceous in age, and this slightly younger Jurassic Daohu Gao biota. And so I've done fieldwork at some of these localities. And unfortunately, this, there's so, there's been so much activity and the local farmers are so eager to recover fossils, that some of these sites are now very heavily protected by CCTV. So as a paleontologist...

• 18:11Speaker 05

  What do you get out of it?

• 18:11Speaker 03

  What do you get out of it?

• 18:13Speaker 05

  Yeah.

• 18:13Speaker 03

  Oh, I mean, well, in terms of some tax site, you can recover thousands of specimens. So there's, there's a primitive bird called Confuciusornis, which is known from thousands of specimens now.

• 18:23Speaker 05

  But you referred early on, Mike, to the thing coming out of Germany, I think it was used, fear, which is about a kilometer or so long. This is hundreds of kilometers long. This changed the game. This is like the sort of meteor into the fossil world, doesn't it?

• 18:37Speaker 01

  Yes, it did.

• 18:38Speaker 05

  The Chinese meteor came and changed, changed utterly.

• 18:41Speaker 01

  It did, because...

• 18:42Speaker 05

  Can you just develop that?

• 18:43Speaker 01

  That's right. And I remember, people would view Archaeopteryx, the German one, as something really unique. And people talked about it as the most valuable fossil in the world, worth a million or $10 million. And then over the years, a number of additional specimens were found. Each raised a great deal of excitement. There are now about 12. As Maria said, from China, there are thousands of individual fossils of the same quality or better. And some of the slabs, you'd swear they make them up, but they don't.

• 19:11Speaker 05

  What is it that preserves them so well in northeast China and in that particular part of Germany?

• 19:16Speaker 01

  Yeah.

• 19:16Speaker 05

  And the Cajun is, we're told, in Scotland. But let's stick with China, because that's the big, that's the big resource.

• 19:21Speaker 01

  You're right. The Chinese, the Chinese ones, they occur in, as Maria said, in numerous localities, over maybe 1,000 kilometers or more.

• 19:29Speaker 05

  Wow.

• 19:30Speaker 01

  And these are just great series of lakes. And they're preserved mainly in the fine sediments that would be settling down through the water in the lakes. And there's a great deal of volcanic activity going on. So people think that has something to do with the extraordinary preservation, that the ash is kind of settling and that has a way of sealing them in.

• 19:50Speaker 05

  What does the ash not let in that's good not to have let in?

• 19:53Speaker 01

  It's, it prevents decay. The key thing is, normally when an animal dies, and if it falls into a lake or just lies on the surface, within a matter of days, the soft tissue will go, either to decay or scavengers. So if you can keep the decay bacteria and the scavenging insects and other creatures out, then you're...

• 20:14Speaker 05

  There's this, sorry, excuse me.

• 20:15Speaker 01

  Then you're in business.

• 20:16Speaker 05

  There's this man called John Ostrom, comes onto the scene. Can you tell us about, give us his dates, please, and tell us about him?

• 20:22Speaker 01

  Yes, so John Ostrom was a great paleontologist in the United States. He was at Yale University. In 1963, he was excavating dinosaurs in the Midwest. He found this remarkable little theropod called Dynonychus. Some people may have seen pictures of this. It's often shown pirouetting on one foot, leaping at its prey, with a great slashing, flick knife type of claw on its hindfoot, and sort of leaping and slashing the side of the prey. And he speculated this was a fast-moving dinosaur. And there was a critical point in 1969, when Ostrom published on this dinosaur, with illustrations showing its extraordinarily

• 21:04Speaker 01

  slender body, that it must have balanced in a remarkable way to be able to achieve these movements. And this was not a lumbering, old-fashioned kind of dinosaur that we'd been used to. And he noted a second thing. He repeated what Huxley had done exactly 100 years before. And he said, this thing is Archaeopteryx. This is a bird. Except we don't see the feathers. But he speculated it would have had feathers. And then soon after, I was at a meeting of the American Society of Vertebrate Palaeontology in New York in 1994. Ostrom was there, as then quite an old man. The Chinese turned up, as Maria said, with these photographs of Sinoceropteryx. This was before it was published. They're showing them around. He was vindicated.

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• 24:42Speaker 05

  Can you give us, can you survey the field, Steve, among which, which of these dinosaurs were feathered and in the mask? Can you pick them out to give us some idea where we are?

• 24:54Speaker 01

  Yeah, these Chinese dinosaurs, they, they really have been a game changer. And I think we're so used to hyperbole about dinosaurs. You know, you see a new dinosaur in the news and it's, you know, a predator the size of a bus or a dinosaur the size of a plane. And sometimes we can overdo it a little bit. But with these Chinese feathered dinosaurs, they are definitively the most important fossils that have been found, at least in, in my lifetime. And they're so important because the preservation is great. You get, you know, this, this volcanic activity helped preserve those feathers. But also because there are so many dinosaurs, there are different species that are found with feathers. And these things really span the dinosaur family tree. So you can map out

• 25:35Speaker 01

  which species have feathers on the family tree, and you can see how those feathers change. And that tells the story of feather evolution, but even more broadly, the story of bird evolution, how a dinosaur turned into a bird. And so what we know now is pretty much any theropod dinosaur, any member of that great group of meat eaters that is found in China in these deposits, has feathers, some kind of feathers, even tyrannosaurs. There's a nine-meter-long tyrannosaur called Eutyrannus there that is found covered in a coat of these very simple hair-like feathers. And then there are lots of other small theropods with simple feathers like that. There are some plant-eating dinosaurs there with simple

• 26:16Speaker 01

  feathers like that. So to me, that indicates, because you have all these meat eaters and plant eaters that have these feathers, that probably feathers go all the way back to the base of dinosaurs. Probably all dinosaurs had some type of feather. But then, this one group of theropods, this derived group of theropods, of manoraptor and theropods, they started to change those simple feathers. For most dinosaurs, that coat of hairy stuff was enough, but these manoraptorans started to lengthen those feathers, the feathers started to branch out, they started to flatten out, they started to evolve the barbs and the barbulles that Maria was talking about. These dinosaurs started to line up some of

• 26:57Speaker 01

  those feathers on their arms, wings formed, these dinosaurs were getting smaller, and it was that group where all of the exciting change was happening, and it was that group that led to birds.

• 27:07Speaker 05

  And getting smaller was very important. And also it changed the idea of the, the great, the great horrible lumberer beast, could move fast, could be swift, could be, it changed the nature of life in the dinosaur world, the perception of it.

• 27:22Speaker 01

  It did. And, and it changed the perception of dinosaurs, really for all of us. And, and even though I, I don't think I'm that old, but I remember when I was in school in the 90s, we still were taught that. All of our books in school had these lumbering, plotting, really stupid-looking, green scaly dinosaurs hanging out in swamps. But I remember in 1997, when the first feathered dinosaur, Cynosauropteryx, was officially named and described, I remember seeing that in the newspaper, growing up in the middle of America, Ottawa, Illinois, little town where I'm from, in the cornfields. And it was in our newspaper. I remember seeing that. And it blew my mind because it was such a different image of dinosaurs.

• 28:04Speaker 05

  Maria, can we come back to you? Can we talk about the differences between hairs and scales and feathers, and how that works in the, in the process of evolution to the feathered dinosaurs?

• 28:17Speaker 03

  Okay, so feathers and hair, they share, you know, they have a lot of common characteristics. They each have, they each grow from a follicle, they each, that follicle is lined by cells from the dermis, the lower part of the skin. They're both derived ultimately from the epidermis, the outer part of the skin. But a main, a major difference between feathers and hair is that feathers are hollow and hairs are not. Hairs have a solid cortex. And they're both known to develop from this structure, this thickened epidermis called a placode during development. And, you know, for years, until recently, there was no evidence for

• 28:56Speaker 03

  these placodes, this developmental structure in reptile skin. So it was thought that feathers and hairs actually were represented two independent evolutionary events, that these two different groups, birds or, you know, dinosaurs and mammals, had each independently evolved these epidermal outgrowths. But then, very exciting, two years ago, a group based in the States uncovered some biochemical evidence for certain, certain, you know, enzymes, genetic precursors for placodes in reptile scales. And then in 2016, so last year, a study looking at

• 29:37Speaker 03

  evo-devo of reptile scales actually found at a very early stage of development, placodes. So you have scales, hairs and feathers, all developing in the embryo from, from the same, effectively the same structure. So the, so the inference is they have a common evolutionary origin. Ultimately, hairs, scales and feathers evolved from the same primitive structure.

• 30:02Speaker 05

  And what does that lead you to?

• 30:04Speaker 03

  Well, so that implies that, you know, the hairs and the feathers we're seeing in these dinosaurs and mammals, they have a common origin. So, you know, really, when we're trying to find, a lot of the work that we do is, we try and understand the deep origins of these structures. The wonderful feathers that we see in, in primitive birds and feathered dinosaurs, they tell us about the end of the story, when things are already becoming quite complex. But I think actually a lot of the interesting part of the story will lie in much older fossils. So trying to uncover the very early steps of evolution of these integumentary outgrowths.

• 30:43Speaker 05

  Mike Benton, can we go back to the archaeopteryx, this supposed first bird? As I understand it, there was, there was a gap in knowing what was going on for almost 50 million years. And various theorists came up, well, said, oh, evolution didn't happen here. Now and then, some event happened and pushed it forward, some horrible monster, or hopeful monster, sorry, hopeful monster, that was the phrase.

• 31:07Speaker 01

  That's right.

• 31:08Speaker 05

  Turned up and pushed the whole thing forward. Let's get over those 50 million years and get on with it. That was more or less what was going on. But then it changed.

• 31:17Speaker 01

  Yes, you're right.

• 31:18Speaker 05

  Archaeopteryx changed that.

• 31:19Speaker 01

  It did. And, and the new discoveries did. Because archaeopteryx was seen as a missing link. People use that term. It doesn't really have any precise definition, but we sort of know what they mean between reptile and, and bird. And it did stand on its own because you had all the dinosaurs, as we've been talking about, flesh-eating dinosaurs and others without feathers. You have archaeopteryx. And then there was a long gap of maybe 50 or 60 million years before further fossil birds. And people said, oh, well, birds don't preserve very well as fossils because they're delicate and small, and they'll tend to disappear, they'll rot away, they won't be found. And so this was then read by evolutionary theorists

• 32:01Speaker 01

  to say, how, how, how did this happen? You know, how do you make a transition from crocodile to bird? They're, they're close living relatives. And so there were some ideas of macro mutations and hopeful monsters, as you say. Around the 1930s, 1940s, and some people thought, yes, that the only way you can make such an enormous transition is to have some extraordinary genetic revolution, something that we don't know about in current genetics. And that made people very uncomfortable because it sounds like a breakdown of normal natural processes. And the risk, of course, of a kind of hopeful monster is it'll be a failure.

• 32:43Speaker 01

  This is like such a huge mutation that the chances of it working. And it's still an argument that confuses people who are troubled with evolution today. They'll say, oh, you look at a bird, you know, you look at a pigeon, and it's so beautifully adapted. It's got lightweight skeleton, it's got a very high metabolic rate, it's got feathers, it's got wings. The adaptation to fly, and we think of human endeavor to make an aeroplane fly. But the point is, then all of these fossils, since the 1990s, have filled these gaps, both before and after. And they show us that half a bird works. You don't actually have to be a complete pigeon. You can be a flyer with primitive feathers and, you know, limited wings.

• 33:28Speaker 05

  Do you want to help us out in this 50 million year gap, Steve?

• 33:31Speaker 01

  Yeah, this is a subject I love to talk about because a lot of my PhD work was on this, and I spent all this time, like, you know, Mike and Maria, very privileged to be able to go to China and study a lot of these new fossils. And really, what they do is, when you map these fossils out on the dinosaur family tree, it tells you that story of evolution. And you can kind of see evolution happening like something of a, you know, running film in action. And what it shows is, you know, this wasn't a hopeful monster situation. A bird was something that emerged very gradually from this one group of dinosaurs over time as piece by piece, it evolved feature by feature of modern birds. I mean, modern birds have a very distinctive body plan. You know, they're small, they have feathers, they have wings, they're lightweight, they

• 34:15Speaker 01

  have wishbones, they could fold their arms against their body, hundreds of things that make birds unique among any other living animals. But these fossils show that those things evolved one by one in dinosaurs over time, and usually for reasons that had nothing to do with flight. They were being evolved for other things. So, you know, the wishbone, it's instrumental for how birds fly today. It's a spring that stores energy in the wings. But that first turns up in small meat-eating dinosaurs that were probably hunting, and so they were, you know, reinforcing their shoulder girdle. So, the same way that whoever invented the propeller, I don't know who that person is, but they would have had no idea the Wright brothers would have put it on a plane, this is what evolution was doing.

• 34:57Speaker 01

  It was changing features of these dinosaurs, and later on, those things would work together to allow this new, small type of dinosaur to fly.

• 35:06Speaker 05

  What was the purpose of the feathers?

• 35:08Speaker 01

  This is such an interesting area of research, a lot of debate now. What fundamentally we know is that these fossils tell us that the first feathers were simple. The first feathers were these downy kind of hair-looking feathers. They were present in dinosaurs like tyrannosaurs and some of the plant eaters that definitely weren't flying. Those animals couldn't fly, they were too big, and those feathers were just like hair. I mean, I can't fly with my thinning head of hair, but I can't fly. So feathers first evolved for something else, probably for insulation. It makes sense, we don't know for sure, but, you know, these dinosaurs were active and energetic, they needed to retain their body heat, so probably the first feathers evolved for insulation.

• 35:49Speaker 01

  But then that one group of small meat-eating dinosaurs changed their feathers, turned their feathers into things that could form wings. But now we see, amazingly, this has emerged over the last few years, that the first dinosaurs with wings couldn't fly either. They were too big, their wings were too small. So it looks like even wings did not evolve for flight. Maybe they evolved as some kind of display billboard on the arms, you know, to attract mates or intimidate rivals. Animals, including birds today, are always using their feathers for display purposes. So I think what we're seeing is a lot of feather evolution had nothing to do with flight, and flight only came later.

• 36:28Speaker 05

  Maria, because of the plethora of stuff coming from China mostly and from other places, and because of the massive development in technology, you can even begin to tell what color, the colors that these creatures had. Can you just tell us a bit about that, please?

• 36:46Speaker 03

  Yeah, sure. So, you know, if, when you look at the feathers of modern birds, and if you crack them open and put them under a powerful electron microscope, you'll see these tiny little microscopic structures. They can look like tiny little balls or tiny little sausages, and these are granules of the pigment melanin. And melanin is just one of the many pigments which modern birds have in their feathers. And what's really remarkable is, over the last 10 years or so, we've come to realize that these, you know, this evidence of melanin pigment can actually survive in fossil feathers. So, you know, several ancient birds and feather dinosaurs have been studied by researchers,

• 37:29Speaker 03

  and we've been looking at the record of color preserved in their feathers using these melanin granules. And what's really remarkable about these melanin granules, or melanosomes as they're called, is that their shape actually varies, and these different shaped melanosomes can generate different colors. So the sausage-shaped melanosomes produce blacks and browns, the spherical ball-shaped melanosomes produce reddish, foxy, ginger colors. And so, for instance, Sinoceropteryx, that first dinosaur that I mentioned that was reported to have feathers, Mike and some colleagues were involved in a study, where they led a study, where they showed that Sinoceropteryx, that those primitive hair-like

• 38:14Speaker 03

  structures, they contain melanosomes, so they're very definitely feathers, they're not just skin fibers. But, you know, what was really exciting was they showed that those melanosomes in Sinoceropteryx are shaped like little balls. So Sinoceropteryx was a ginger dinosaur.

• 38:33Speaker 05

  Can I come to, so you discovered the ginger dinosaur?

• 38:36Speaker 01

  Indeed, yes.

• 38:37Speaker 05

  Well, that's something to do, isn't it? I mean, most of us don't get anywhere near that. Can you tell us about the Mani Raptorans, how they add to the emerging picture? We're still on wings, aren't we? Are we getting towards wings?

• 38:50Speaker 01

  We are indeed, and it seems that the two things were happening, as we've mentioned, that mostly in the theropod dinosaurs, they had a trend to large size and shortening the arms, and we think of T. rex as a kind of end of the story. And every child will tell you that the arms are so short it couldn't even reach its mouth. But in the Mani Raptorans, the name means hand hunter. Their arms were extending, and this is what Ostrom noticed in Dinonychus, which is a Mani Rapturan. And we now know that the extension of the arm was so that it would carry feathers, but the shrinking of size was happening at exactly the same time. So there's miniaturization and extension of the arms.

• 39:32Speaker 01

  And as Steve said, these were not flying, or they may have been able to use them at times for gliding, just by spreading them out. But almost certainly, they'd be using them for other purposes. And the discovery of the ginger color, it wasn't just ginger in Sinoceropteryx, it is a Mani Rapturan, it is a dinosaur. The tail was striped like a barber's pole, so it was repeated regular stripes of ginger and white, ginger and white, ginger and white. And the rest of the body was covered with sort of ginger color over the back, and maybe pale on the belly, and various patterns over the face. And so we were thinking, why would it have a stripy tail? Could this be camouflage? You think of a tiger or a zebra. No, because it's only the tail.

• 40:16Speaker 01

  Why camouflage your tail but not the rest of your body? Therefore, display. And as Steve mentioned, this actually shifts behavioral functions, bird-like behavior, down. And so we imagine these little dinosaurs hopping around, waving their tails and saying, "Look at me."

• 40:31Speaker 05

  Can I come to you then, Steve? Looking, as it were, researching backwards, what does your present study of birds tell us about where they came from?

• 40:42Speaker 01

  Well, we now know, you know, unequivocally, nobody really argues this anymore among paleontologists, that birds came from dinosaurs. And what that means, it means a lot of things, but one thing I would just like to highlight there is that it helps us, this realization helps us understand dinosaurs better. It helps us understand T. rex and Triceratops and Brontosaurus better, because we know that they have living descendants. And so this helps us to better understand how these ancient dinosaurs, which oftentimes are so out of scale to anything that's around today, it helps us to at least better envision what they were like as real animals, as things that had to grow and feed and move.

• 41:26Speaker 01

  And we now recognize that, by and large, dinosaurs, whether it's T. rex or these enormous creatures like Brontosaurus, they were much more bird-like in their behaviors than lizards or crocodiles. So all of this has led to a bit of a new picture of what dinosaurs were like, and I think it's brought dinosaurs to life in a way that we could have never imagined before these fossils were found.

• 41:49Speaker 05

  Maria, can you explain the uneven distribution of feathers among the dinosaurs?

• 41:54Speaker 03

  Okay, so, you know, one thing that has emerged in recent years is a picture of how birds acquired feathers and, you know, what we would conventionally consider wings. And what we now understand is that there wasn't a progressive change whereby feathers gradually became more complex over time. It's actually a lot more complicated than that. Feathers and wings, they evolved in a really piecemeal fashion. So for instance, you know, you have some early feather dinosaurs, like Ankyornis, which has, you know, beautiful veins, so complex feathers on the forelimbs and the hind limbs.

• 42:37Speaker 03

  But then you look at some younger fossils like Sinoceropteryx, and it doesn't have feathers that are this complex at all. So what's happening with feather evolution, the evolution of wings, it's more like a mosaic, different features, so the hind limbs and the forelimbs and the tail, they're all almost evolving independently. And these changes towards a bird-like appearance, they're happening in kind of spurts in different dinosaurs.

• 43:02Speaker 05

  Mike, Ben, can I come back to you? When, in this 50 million year span, when did they actually start to have proper wings and fly so we would recognize them among the birds today?

• 43:13Speaker 01

  Yes. I think that's archaeopteryx. So the interesting thing is there has been stability.

• 43:17Speaker 05

  When did he come along?

• 43:18Speaker 01

  So that's about 150 million years ago, at the end of the Jurassic. And so we have fifty million years leading up to that. So just to make it really clear, when I was taught and when I started to teach as well, archaeopteryx stood there as the possessor of maybe fifty unique bird characters. And now almost all of those features have gone back, as Steve was saying, the wishbone, the hollow bones, the small body size, the development of wings in manoraptrons. So virtually all of these uniquely bird characters have sort of gone back down the evolutionary tree, being acquired piecemeal. And so archaeopteryx is still characterised, and we would say birds as well, by the ability

• 44:00Speaker 01

  to fly in a powered way. That means beating the wings up and down with the complex of muscles and using that wing beat to keep aloft.

• 44:09Speaker 05

  So let's get, let's nail it. I was, the millions are rather baffling me. When, about when? You're within a couple of million years.

• 44:15Speaker 01

  Yes, yes, yes. So the process would have begun over two hundred million years ago with the Origin of Dinosaurs. And then at a hundred and fifty million, you have archaeopteryx with proper muscular wing beats and powered flight and the first bird, as most people would say. And then you carry on in, going through into further Chinese deposits and, and good record of birds right through to sixty-six million years ago, the extinction of the dinosaurs, the extinction of a lot of these early bird types, and then the massive explosion of modern birds and ten thousand species of birds today.

• 44:50Speaker 05

  How revolutionary have these discoveries been, these last few years' discoveries?

• 44:56Speaker 01

  To me, these are the revolution, in my lifetime at least. And I think they have changed our perception of dinosaurs. I think they're starting to change the public perception of dinosaurs. Of course, the public perception takes some time to catch up sometimes with the, the scientific way of seeing things. But they, it, it's, it's hard to really overstate their importance. And they are beautiful fossils. A lot of these look like they should be in art museums. They are a thrill to study. And farmers across Liaoning province in, in China are finding these every day. There are farmers out right now, I'm sure, that are finding more of these fossils. So this revolution is not ended, it is still ongoing. And who knows what the next big find is going to be, but it'll probably happen in the next

• 45:40Speaker 01

  few weeks. So everybody should keep their, you know, eyes peeled to the news.

• 45:44Speaker 05

  Peeled on northeast China and forget about what's happening in Beijing or anywhere else. Mike, come back to you for a moment. Why did they survive when none of the other dinosaurs did?

• 45:56Speaker 01

  And, and, and that's a very difficult question, because in fact, very many of the birds did die out at the same time as the dinosaurs, the, the heavier dinosaurs did at sixty-six million years ago. And so why a number of very weird-looking duck-like creatures, which were the precursors of the modern birds, survived through that crisis? We don't know. They're small, but that doesn't save them from everything. They, they, they were, they had high metabolic rates, so a big need for food. Because people used to say, oh, well, turtles and crocodiles survived, they just burrow into a hole and just kind of sleep it off and crawl out a week later and the meteorite is gone and everything is kind of... But no, so frankly, that is a mystery, because the, the, the, the lifestyle

• 46:40Speaker 01

  of the birds that survived would have been almost certainly similar to that of the primitive forms that went extinct. So that is still a mystery that may not be solved.

• 46:49Speaker 05

  Maria, what's the most pressing question you have that you want answered by these fossils that are coming through every day according to Steve? I mean, as we speak, it's probably mountainous. Anyway, never mind.

• 46:59Speaker 03

  Okay, so, so there are, there are two main, there are two obvious areas that we need to be focusing on in terms of understanding feather origins and feather evolution. So for instance, we now know that two major groups of dinosaurs, the theropods and the ornithistsians, had feathers. And as far as we're currently aware, the third major group of dinosaurs, the sauropods, didn't. So, and this is a major thorn in the side of people like myself and Mike, you know, and, and Steve, we all believe that dinosaurs evolved very, that feathers evolved at the base of dinosaurs. We need to look for feathers in sauropods. And to really understand, we need to go way back into, into groups that

• 47:44Speaker 03

  are older than dinosaurs.

• 47:46Speaker 05

  Well, thank you very much, Maria McNamara, Mike Benton and Steve Brusatti. Next week we'll be discussing Guernica by Pablo Picasso, the painting and the events in nineteen thirty-seven. Thank you very much for listening. And the In Our Time podcast gets some extra time now with a few minutes of bonus

• 48:01Speaker 01

  material from Melvyn and his guests. Yes, that was very quick.

• 48:05Speaker 03

  I didn't realise you were so, so tight at the very end. I thought I had another half a minute.

• 48:10Speaker 05

  Yeah, you, you have to sort of risk being rude, I know, which is awful, but yet there's no other way.

• 48:17Speaker 01

  And Maria, you didn't get on to the molecules and the survival of organic matter.

• 48:21Speaker 03

  No, no.

• 48:22Speaker 01

  But there we are. Because that's, that's an important question that people have difficulty with.

• 48:27Speaker 05

  That's right.

• 48:28Speaker 01

  Yes, yes. So the question is, and I'll pass it to Maria, which is, people report DNA, people report red blood cells, they report all kinds of extraordinary organic survival in fossils. What's the current position?

• 48:39Speaker 03

  So the current position is, there's, if you find DNA in a young fossil, like a, like a mastodon or a woolly mammoth, that's about a hundred thousand years old, people aren't going to have a problem with that. But DNA and, you know, other biomolecules, proteins, tissues like feathers, which are made of the protein keratin, these molecules are much more, are very decay prone, and they're not going to hang around over millions of years on geological timescales. So claims that these kinds of biomolecules can survive are very, very controversial. And a lot of them are based on evidence from techniques that paleontologists, quite frankly, don't use. So we don't know how to test the...

• 49:20Speaker 01

  Chemically, what, what about melanin? I mean, what's the thing about melanin?

• 49:23Speaker 03

  Okay, so, you know, melanin, we, we all know that there's, there's really good and robust chemical evidence for survival of the melanin biomolecule in some of these Chinese fossils. So people have used various different techniques. You know, there's two or three key techniques that you can use to show that the molecule is surviving, as well as the actual physical granules themselves. So they're not, as some people claim, that they're not decay bacteria. Basically, you have these little granules, and they look like melanin granules, and they contain melanin. The most plausible interpretation is that they are melanin granules.

• 50:02Speaker 05

  They look like a duck and walk like a duck and talk like a duck.

• 50:04Speaker 03

  Then it's got to be a duck, exactly, yeah. But survival of melanin, you know, it's not too surprising, because it's a really tough molecule. You throw acids at it, you throw alkalides at it, and it doesn't degrade. The only thing that degrades melanin is really strong concentrations of peroxide. You've got to really oxidise it really heavily to, you know, destroy it. So that's why, you know, you look at a fossil feather in a dinosaur, the feather is preserved because of the melanin, you know? And this is another big question. Well, if that's the case, where's the keratin gone? Is there any evidence for keratin survival? So this is a question that some of us are working on now. You know, can we find any

• 50:46Speaker 03

  traces of keratin associated with the feathers? But keratin is more decay prone, it's going to be harder to find, and you've got to have better evidence.

• 50:54Speaker 01

  There you are, another programme. People are trying to bring...

• 50:59Speaker 05

  When, when you, well, I did give you the air to, to mass a few more fossils.

• 51:02Speaker 01

  That's right.

• 51:03Speaker 05

  What did you, didn't, what did you not say that you would like to have said, Steve?

• 51:06Speaker 01

  I'll just, you know, put out a pitch. I mean, we all teach and we all have a lot of students that are, you know, fascinated with this stuff. And, and there's so many opportunities, I think, for the next generation. There's some big mysteries still to solve. So I think, you know, for anybody who's listening out there, who's kind of a young, budding paleontologist, or thinking of studying this stuff, whether you're back home in, you know, the Midwest US or up in Scotland or in China, indeed, wherever, somebody needs to go out and find a feathered sauropod, that's going to be a big deal. Somebody needs to find some older fossil feathers. Everything we have with these feathered dinosaurs is either Jurassic or Cretaceous in age. And so a lot of the big moments in evolution of dinosaur feathers and in the early part of the Origin of Birds, we're not really recording it in

• 51:48Speaker 01

  the fossil record. We're seeing signs of it in these Jurassic and Cretaceous rocks, but a lot of it was probably actually happening earlier. So if somebody can find some of these sites that preserve feathers, and it's hard to do, if it was easy, people would have found them. So you need a bit of luck, but that would be a big game changer. And then the big question for me, or one of the big questions, is how did flight actually evolve? I mean, we know that these dinosaurs are changing, they're getting smaller, they're changing their skeletons, they're developing feathers, they're turning their feathers into wings. But how did evolution actually make that step to allow these things to start moving about competently in the air? And so that's going to require a lot more than just finding fossils. It's going to require a lot of interdisciplinary work, probably

• 52:32Speaker 01

  a lot of engineering-style work that is a little bit beyond normal paleontology. So I think there's some great opportunities for, for future work.

• 52:40Speaker 03

  And another area that people haven't looked at at all is, and it's almost like an elephant, the elephant in the room. You know, if dinosaurs are evolving feathers, you can't just have a feather sticking out of a scale. You have to have a very modified skin structure to actually hold those feathers, to be able to manipulate them, control their direction. So what we actually should be looking for as well is, you know, features of the skin that have co-evolved with the feathers, to enable feathered dinosaurs to manipulate their feathers, to control them, because these are all characters that are really important for flight. So we should be looking at also preservation of the skin in these feathered dinosaurs as well.

• 53:18Speaker 05

  What about you, Mike?

• 53:19Speaker 01

  I agree with her. I agree with him. Nothing more to say.

• 53:24Speaker 05

  If I did that, the purgatory would end at about quarter past nine. You're the man. He's the producer, just in time.

• 53:34Speaker 01

  Maria's got a train and we promised her. You've got a taxi.

• 53:37Speaker 03

  Yep.

• 53:38Speaker 01

  Yeah.

• 53:39Speaker 00

  Thank you for listening to this archive episode of In Our Time. Every Monday, I revisit one of more than a thousand episodes in our archive. And on Thursdays, you'll still find brand-new episodes of In Our Time. Listen first on BBC Sounds or wherever you get your BBC podcasts. This Cultural Life from BBC Radio 4. I will never go into anything so deep like that again. The world's leading artistic figures reveal their creative influences. Disobey, disagree, disavow. I'm John Wilson, and my recent guests have included the sculptor Anish Kapoor, photographer Annie Leibowitz, the actor Kristin Scott Thomas. It has made me good at telling stories about people who have a secret suffering. And former children's laureate Frank Cotterill-Boyce.

• 54:24Speaker 00

  If art's got one function, it's to point to what's wonderful and say, look, this is your world, it's insane. Listen to This Cultural Life on BBC Sounds.

• 54:38Speaker 00

  Ever wonder how a single court decision will change the direction of the USA? That's the idea behind Let the Records Show, a new podcast from the ACLU, hosted by history teacher Matt Beat and journalist Shereen Marisol Miraji. Each episode digs into a landmark ruling and the human story behind the law. From Wong Kim Ark, whose case gave us birthright citizenship, to Paulie Murray, the trailblazing activist, lawyer and Episcopal priest who pushed the USA to take racial and gender equality seriously. Tune in every other week, wherever you get your podcasts.