Pod Insights The Ancients The Age of Dinosaurs with Henry Gee About this episode Before Tyrannosaurus and Triceratops, Earth was rebuilding from catastrophe. Out of the ashes of the Great Dying rose a new prehistoric world and with it came the age of the dinosaurs.
In this episode of The Ancients, Tristan Hughes is joined by Dr Henry Gee to explore the full sweep of dinosaur history, from their emergence on the supercontinent Pangaea to their 150-million-year dominance of the planet. Discover how early reptiles evolved into the giants of the Jurassic and Cretaceous, how ecosystems transformed around them, and why their reign finally came to a dramatic end.
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Rise of Humans
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Feathered Dinosaurs
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Presented by Tristan Hughes. Audio editor and producer is Joseph Knight. The senior producer is Anne-Marie Luff.
All music courtesy of Epidemic Sounds
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Transcript 13,170 words · 4 speakers
Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.
0:00 Tristan Hughes? Ever wondered why the Romans were defeated in the Teutoburg Forest? What secrets lie buried in prehistoric Ireland? Or what made Alexander truly great? With a subscription to History Hit, you can explore our ancient past alongside the world's leading historians and archaeologists. You'll also unlock hundreds of hours of original documentaries with a brand new release every single week, covering everything from the ancient world to World War II. Just visit historyhit.com/subscribe.
0:32 Speaker 01 Hey, we're Nick and Jack, hosts of The Best One Yet. Behind every episode, there's research, emails, spreadsheets, and our shared Google Doc, the Headline Hammer. With Google Workspace with Gemini, Google's AI is built right into the premium versions of tools we already use, like Gmail, Docs, and Sheets. No new tools or extra logins, just personalized AI for the way we work. That means less time on the work around the work and more time finding the stories worth talking about. Get AI tools for work. Upgrade to Google Workspace with Gemini at goo.gle/workspacewithGemini. That's goo.gle/workspacewithGemini.
1:08 Tristan Hughes? Hello, I hope you're doing well. And I have a question for you today. I want to see answers in the comments. What is your favorite dinosaur? Because that is what we are covering today. We are covering the whole age of dinosaurs. So over 100 million years of paleontology, from Triassic to their extinction, with a fan favorite guest returning to the show, none other than Dr. Henry G. I loved doing this conversation. You're going to hear what my favorite dinosaur is, what Henry's favorite dino is, and so many other things. I think my favorite part of this interview was addressing the question of whether dinosaurs did swim or not. Still one where there's a big bone of contention around it.
1:53 Tristan Hughes? But we covered that and so much more. Henry, as always, he's funny, but he's also incredibly engaging at the same time. I really do hope you enjoy. Let's go.
2:16 Tristan Hughes? Two hundred and fifty million years ago, our world witnessed the greatest mass extinction event in its 4.5 billion year history. Ninety percent of life was wiped out. It's known as the great dying for a reason. The world took millions of years to recover, but ultimately, it did. This great dying beckoned in a brand new prehistoric world. At this time, Earth still only had one giant continent known as Pangaea, and it soon became full of new and diverse life. There were giant crocodile-like apex predators, herds of bizarre heavy herbivores, small
3:01 Tristan Hughes? creatures that burrowed into the soil, the earliest mammals. And amongst all of this emerged a group of reptiles that would go on to dominate the world: the dinosaurs. For over a hundred million years, dinosaurs would rule the lands, diversifying into all shapes and sizes: from great carnivores, to armor-plated plant eaters, to small feather-covered raptors, until they too ultimately fell foul to their own mass extinction. Today, we're going to talk you through their story from beginning to end. More than a hundred million years of dinosaur history.
3:41 Tristan Hughes? This is The Age of Dinosaurs, with our fan favorite returning guest, Dr. Henrichi. Henry, legend of paleontology, it is wonderful to have you back on the podcast.
3:55 Speaker 02 Thank you very much, Tristan. Legend, I'm more of a myth.
3:58 Tristan Hughes? You're more of a myth, okay. Well, today, we've got a big topic, Henry, but we always have big topics with you. We've done the origins of life on Earth, and we've done the rise of humans. Now, we're going to cover the age of the dinosaurs from beginning to end. In about 60 minutes or so, it's another big task. Are you ready to give it a go?
4:18 Speaker 02 I'm ready.
4:20 Tristan Hughes? Fantastic. So, with the age of the dinosaurs, Henry, where should we begin? I mean, when are we talking?
4:26 Speaker 02 I think you should cast your mind back, if you will, to about 250 million years ago.
4:32 Tristan Hughes? Right.
4:32 Speaker 02 This is somewhat before the dinosaurs came along, but it was a very important moment in the Earth's history.
4:39 Tristan Hughes? So, 250 million years ago, what's happening?
4:43 Speaker 02 That was the Great Dying. That was the end of the Permian period, when a series of supervolcanic eruptions released toxic gases into the atmosphere and poisoned the sea and resulted in the extinction of 95% of all life in the sea and over 70% on land. So this was the Earth's greatest attempt to extinguish life in the past 500 million years. But that was followed by the terrific Triassic period and it was in that that the dinosaurs and many other things originated.
5:23 Tristan Hughes? And this seems important to highlight straight away. So when talking about dinosaurs, in the story of the emergence of life on Earth, they actually come about pretty late in the story. So, you know, before 250 million years ago, we've got all of these other creatures that once reigned the Earth before the dinosaurs come to the fore, or at least just emerge onto the scene in the Triassic.
5:43 Speaker 02 Yes, what happened was after the Great Dying at the end of the Permian period, life, as you know, has a motto which is whatever doesn't kill you makes you stronger. So the Triassic period, which if anyone were going to ask, is my favourite period of the whole of life, that was a triumphant raspberry to the end Permian extinction. And after a few million years, in which life got its breath back, during which there was basically one genus of reptile that mattered, Lystosaurus. Lystosaurus was no, it was more closely related to us than to dinosaurs, but only very distantly.
6:23 Speaker 02 Lystosaurus was a cross between a pig, a golden retriever and an electric can opener, and it used to go around hoovering up everything on the Earth, and it was a kind of a disaster tax on. But after a while, other things came out. From from under there where they were hiding and there was a tremendous evolutionary radiation of all kinds of bizarre reptiles, the like of which have never been seen, had never been seen before and died out during the Triassic period, which was lasted fifty million years. So there were all kinds of completely bonkers aquatic reptiles, many of which died out, but some which persisted like the famous ichthyosaurs, which became
7:05 Speaker 02 to look like dolphins. And the largest ichthyosaur, shonyosaurus, lived in the Triassic period. It was about twenty one metres long. It was a big beast. And various other crazy things. There were things like tannistrophius, that was a kind of lizardy thing with a neck that was longer than its body and tail combined. There was a strange flying reptile called sharovictorix, in which the wings were formed by the hind limbs, leaving the front limbs free, which is completely back to front. And there were some other very strange creatures called drapanosaurus. And there were, there was the emergence of things that we see today,
7:46 Speaker 02 lizards, the ancestors of snakes, the earliest mammals, frogs originated, but also some other things, pterosaurs, the flying cousins of dinosaurs, originated in the Triassic. And there were all kinds of gigantic crocodile like things called rauisukians, which were huge predators. They were quadrupeds, but some had heads that looked like tyrannosaurus. They were big, ferocious carnivores. But in the middle of the Triassic emerged the dinosaurs. And for a long time, they were just the kind of second violins in the orchestra of reptiles behind the star soloists. But they originated in the middle of the Triassic,
8:30 Speaker 02 amid all this flourish of biological diversity. And if you were to go and visit the Triassic period, you'd not know or suspect that these unassuming crocodile like reptiles among a whole load of others would one day inherit the earth.
8:47 Tristan Hughes? And just also to paint more of a picture of this Triassic world, Henry, you know, following that massive extinction event, do we know what the Triassic world looks like for those earliest dinosaurs and all of the other animals that were roaming the world at that time?
9:05 Speaker 02 In the Triassic, the all the major land masses of the earth were united into a gigantic supercontinent we these days called Pangaea. And if you were to look at it, it was a kind of a C shape. It extended almost from pole to pole. In the the Gulf of the Sea, that was what was called the Tethys Ocean, and there were various islands and other little continents in there. One was South China, which at that time was a kind of land that time forgot. That was a kind of strange island continent with all sorts of ancient relics. But the the climate was very, very extreme. Because water could flow to the North Pole and the South Pole, there wasn't the extreme
9:48 Speaker 02 contrasts of weather that we see, of climate that we see today. There was no ice, there was no permanent ice caps. However, the Tethys Ocean, because of the surrounding continent, had very extreme climates. It was a kind of mega monsonal climate. And also because Pangaea was so huge and quite a lot of it was far from the sea, there were some very, very hot deserts in Pangaea. So not the climate, but the general, well, yes, the climate of Pangaea generally was very different from the the very zonal climate we have today, but there were still great extremes of temperature and and weather and precipitation.
10:29 Tristan Hughes? And do we get different kind of ecosystems in this great landmass depending on the climate and the location? So do we get particular animals rising to the fore in certain places before the dinosaurs become the top predators and the top species, I guess?
10:42 Speaker 02 Yes. Things like Lystosaurus and other reptiles lived more or less everywhere, but certainly in the towards the poles, these were the lands where giant relic amphibians lived. Huge predatory salamanders were in the watercourses. In the tropics, various things live, but things don't fossilize well in the tropics. But certainly in the deserts, that's where mammals originated. The little tiny mammals, which were tiny things the size of shrews, were basically not. And evening and early morning feeders, they used to live in their burrows when the temperature was very, very hot. And come out in the morning and the evening. And we know even in in those early times.
11:27 Speaker 02 Some of these animals had already specialised, some had teeth that could crush beetles and others lived on on moths. Which are softer and as we know, a moth is a male myth. Um. So, uh, but the dinosaurs originally lived at more temperate. Latitudes along with various other reptiles and that's where they were kind of confined for quite a long time.
11:51 Tristan Hughes? And so take it away, Henry. What do we know about these earliest dinosaurs and where they were living and what distinguished them? From those other great creatures that were front and centre at that time in the Triassic?
12:03 Speaker 02 The dinosaurs started as kind of rather graceful quadrupeds. Think of them as kind of greyhounds with small heads on long necks and possibly like boars always. They were related to creatures such as silos or a thanos, which are reptiles, which are kind of graceful. And live and ran around on four legs like like kind of fast dogs. But there were a lot of other creatures like that. That are related more closely to modern crocodiles, which used to be very much more various in their forms than they are now. Among this group of creatures were the lager pertids, which were similar, which which were probably more closely related to the.
12:47 Speaker 02 Terror source, although the actual transitional form of terror source is unknown and they appear in the Triassic with wings. More or less fully formed. So the ancestry of terror terror source is a big question mark. But the dinosaurs seem more closely related to these four legged things. And they evolved in the kind of temperate regions. Into bipeds and it was that that really marked their success. Now, there were other bipedal creatures uh uh related to them, but it was something about the balance and poise of these creatures with straight backs, long legs, long tails to counter to counterbalance their bodies and necks.
13:31 Speaker 02 And and initially rather small heads and they were quite fast runners and they were kind of chicken sized creatures. I could tell you an anecdote about some of the chickens we had in the G family, which you'll probably cut out, but I'll tell you anyway. Me and Mrs. G like to adopt ex battery chickens and most of these are free range, but occasionally we have adopted chickens that come from battery farms and they're baldies. They don't have many feathers on and you have to have them with little jumpers to start with. But also because they're battery farms, they're completely unsocialized. So we had a few of these chickens in the garden and I watched from the back door as Mrs. G was chased round and round by these vicious little creatures.
14:16 Speaker 02 And she came back in and said, don't go out. It's Jurassic Park out there. So anyone who thinks that birds aren't dinosaurs, birds and dinosaurs aren't relatives, has never kept chickens. But I digress. The earliest dinosaurs were rather like this. And the earliest dinosaurs that we know about tend to come from deposits in southern Africa and Argentina. And they're already showing signs of diverging into the major groups of dinosaurs. There were the small meat eating types, some of which grew to quite large size. Hererosaurus was a very early meat eating dinosaur that was a couple of metres long, maybe more, quite big.
14:57 Speaker 02 But they were also specializing to be herbivores, the ancestors of these gigantic land whales of the of later ages like the brachiosauruses and the diplodocuses. But these were kind of prosauropods, not the sauropods, which are the big ones. And these were quite big. They had small heads, long necks, not as long as they were going to be and could often be bipeds. Platiosaurus is one that's very well known from lots of remains in Germany particularly. But already in the Triassic, they were beginning to specialize. And as the Triassic progressed.
15:35 Speaker 02 The dinosaurs slowly began to fill ecological niches that were left by other reptiles that were becoming extinct, because evolutionary extinction is just the normal cause of of what happens. Extinction is basically God's way of telling you to slow down. So there were various kind of reptiles that herbivorous reptiles that became extinct and the the sauropods fills those gaps. Similarly with the kind of more predatory alligator type rowasukians, the carnivore, the carnivores filled those filled those gaps. They were still eating some of the reptiles that were hangovers of earlier ages. In the Triassic, the descendants of Lystrosaurus, that kind of
16:19 Speaker 02 disaster taxon, grew into enormous forms the size of cows or rhinos. There's one called Placerius that looked like a kind of rather depressed moving sofa that was eaten by these things.
16:33 Tristan Hughes? Henry, you really, you really do down the Lystrosauruses and the Placerius.
16:37 Speaker 02 Oh, no, no, the Lystrosauruses were fantastic. They were my favourite fossil reptile of all time because they were so brilliant, filling in all the holes. They ate everything and didn't really, like golden retrievers, they didn't really care whether it was really edible or they'd just eat it. And these, we know a lot about these creatures, these things that were proto mammals, because a lot of them made burrows, and that's how they withstood all these mass extinction events. We have fossils of them still asleep in their burrows. These are known mainly from southern Africa, the great Karoo beds. They've been known for decades and decades. But they're also known from Russia, a lot from Russia and other places.
17:18 Speaker 02 But the dinosaurs we first pick up in South America and South Africa. Also, there's another great radiation of dinosaurs, the so-called ornithiscians, that would eventually give us the armored dinosaurs, Stegosaurus and Cardosaurus, Triceratops, my my wife's favourite dinosaur. But these were at the time, small bipedal creatures as well. Maybe they were distinguished by variations in their. Their teeth, it's the dentition that usually leads evolution in these things. But it was only because various other creatures were becoming extinct that the dinosaurs slowly, slowly, slowly became more common.
18:02 Speaker 02 So that by the end of the Triassic, they were pretty much it. But there were still major hurdles to overcome.
18:11 Tristan Hughes? Before we go on, Henry, you did mention one phrase, important phrase in there that I think is important also. To clarify what we mean by it, ecological niches, what are ecological niches?
18:22 Speaker 02 Well, ecological niches are the kind of living space in which creatures live. So an ecological niche could be a herbivore that browses on tall trees, for example. So if there are already lots of herbivores living around that browse on tall trees, there's no room for other creatures to evolve into that space, as it were. Similarly, you have ecological niches, you have large carnivores and small carnivores and middle sized carnivores. And each one occupies a different space in the ecosystem so that they can all live together. So that in the middle Triassic, there were already large, small and middle sized herbivores and large, small and middle sized carnivores. So with the dinosaurs, when they evolved, had to kind of hang around.
19:07 Speaker 02 They were very marginal, they had to to wait till their turn came until all the other ones became extinct or scarce, so they could move in and occupy those same niches. Because all sorts of other things were happening at the time. Plants were evolving a lot, insects were evolving a lot. The landscape, even though I painted the picture of Pangaea as this great dollop of a supercontinent, the climate in that was changing all the time, it was Pangaea was moving around. There was lots of volcanoes going off and there were long spells of calm. And then there were periods of great turbulence, so life wasn't static.
19:43 Tristan Hughes? So let's go forwards now to the end of the Triassic. So Henry, very briefly, what time period are we talking about that we usually mark as the end of the Triassic period? Is that 220 million years ago?
19:55 Speaker 02 About about 200, about 200.
19:57 Tristan Hughes? 200 million years ago.
19:58 Speaker 02 It was a long, interesting period, and I have to say, we are talking about the dinosaurs, but I want to. Bang the drum for the Triassic, because we tend to think of the Triassic as the period in which dinosaurs appeared and forget all the other amazing things that happened in the Triassic. And we forget to realise that the dinosaurs for a long time, for at least the first half of the Triassic, were very, very minor features of the fauna and tended only to live in particular places. They didn't live all over the world, which they were to do later. But the end of the Triassic was marked by one of these gigantic mass extinctions. It was one of the big five. I mean, the end Permian that began the Triassic was the biggest. And but the the end Triassic was definitely there in the top ten and actually
20:43 Speaker 02 in the top five of our extinction hit parade. And that was another volcanic event. It was a bit slower to take to to happen. What happened was Pangaea was beginning to unzip. There was a fault line in Pangaea, as you remember in continental drift. North America was basically glommed up against North Africa and Europe, up to as far as Norway and Greenland. And that was a very, very old seam that had been an ancient mountain range, which before had been an ancient ocean. But it now forms the that those old mountain ranges form the
21:22 Speaker 02 Scottish North West Highlands and the Appalachians, very old mountains. But along that seam, there was a rifting, a bit like the current rift valley in Africa. What happened was the continents were beginning to pull apart and sediment slumped into the middle and formed lakes that came and went until eventually the ocean came in. That was the that seaway was what eventually became the Atlantic Ocean. And that caused Pangaea to start to split up. And it was a lot of volcanism at the time, and climate changed radically. And the end of the Triassic saw the extinction of all this, all these amazing reptiles that
22:07 Speaker 02 evolved in the Triassic, the all these weird things only ever lived in the Triassic. And only a few things came through. It spelled almost the end of the giant amphibians, although some of them did hang on to the Cretaceous. The ichthyosaurs hang hung on and the ancestors of what became those other great marine staples of the of the dinosaur age, the pleistosaurs, they hung on. But and so did the pterosaurs and the mammals and of course the dinosaurs. They managed to hang on and replace everything that everything they hadn't originally replaced on land. So they became the the dominant group of creatures on land at the end of the Triassic after that great rifting.
22:52 Speaker 02 And I remember a cartoon I saw in Punch once of a large, rather dim looking dinosaur standing over a widening crack in the earth and a small, intelligent looking dinosaur says, I'd make your mind up soon if I were you, the continents are beginning to drift apart. So it was in that landscape that the dinosaur, the early Jurassic period, which followed the Triassic, that the dinosaurs really came into their own.
23:19 Tristan Hughes? I mean, Henry, it's fascinating because we always associate the dinosaurs with, you know, they're ultimately going extinct with the other extinction events that we'll get to later.
23:28 Speaker 02 Yes, spoilers, spoiler alert.
23:30 Tristan Hughes? Well, I'm sorry, I'm sorry to to jump ahead. But what I was saying there is that we forget that actually dinosaurs earlier on, they did survive another extinction event where so many other animals didn't. Now, why do you think the dinosaurs survived this extinction event when so many other animals don't?
23:48 Speaker 02 No one knows. This is the great thing about extinctions, it's kind of a lottery. Extinctions are basically the sum of a lot of tragic individual deaths. And even though maybe a lot of dinosaurs died, a few survived. And it was maybe just a lottery that the, I don't know, Placodons or Rauisukians or all these other reptiles in the where are they now files didn't survive. So a lot of these things were very similar to each other. So it was probably a bit of a lottery that that they, that some survived and some didn't.
24:22 Tristan Hughes? So we get to the beginning of the next period. So the Jurassic period, as people think of Jurassic Park and so on, although I do like your chapter in your book, which says Triassic Park, I thought that was great. But we emerge into the Jurassic world post this extinction event. Henry, paint us a scene of what this new world looks like, where, you know, at least some dinosaurs have survived. And now this is almost their new kingdom.
24:45 Speaker 02 The world was beginning to split up into into various continents. It was beginning to come separated into different continents. And this is great for evolution, because it means that different continents can have a different range of animals that to evolve specifically on those continents. I mean, we think now of marsupials that only live in Australia and so on. Well, that happened in the early age of the dinosaurs, and that was key to their evolution. They evolved, we tend to think of the very, very large dinosaurs that evolved in the Jurassic, the kind of gigantic Brachiosaurus and Allosaurus, which was a major carnivore in the Jurassic. But there were successions of different waves
25:30 Speaker 02 of these things that throughout the Jurassic and the subsequent Cretaceous period, there were different radiations like the Abelisaurus, which were specifically South American carnivores. And Europe was a mostly underwater at the time. There are whole stretches of the Jurassic where there are no terrestrial rocks from the Jurassic in Europe. And so Europe was like an archipelago of islands, and there were dinosaurs that evolved each on different islands. And some were quite small, because islands produce dwarfism. So there was a kind of cute elephant-sized sauropod. And Madagascar, probably later in the Cretaceous,
26:13 Speaker 02 Madagascar an island we know even today that has a very highly endemic fauna with lemurs and things, only live in Madagascar, it had its own dinosaurs. And so dinosaurs evolved in various ways, but they were usually of these three basic forms. They were the bipedal carnivores, they were the big quadrupedal herbivores, the sauropods, and a rash of armored dinosaurs. It was things like Stegosaurus that started to evolve in the Jurassic. That's a characteristic. North American dinosaur, although they were relatives all over the northern continents, there were some from China, of course.
26:55 Speaker 02 But of course, what we forget, because we don't realise that there were these waves of different dinosaurs that rose and became extinct, we tend to think all the dinosaurs came together. So when you see pictures of Tyrannosaurus battling with a stetosaur, that is as anachronistic as seeing Raquel Welsh battle with a triceratops. Because when Tyrannosaurus was around, Cegosaurus had been extinct for tens of millions of years. And Tyrannosaurus would have battled with ankylosaurs or, or, uh, ceratopsians like triceratops. Waves of herbivores came and went. The earlier sauropods were replaced by even bigger, better ones called titanosaurs.
27:38 Speaker 02 Eventually, and these were, you know, in the Cretaceous, eventually in the Cretaceous, these sauropods declined a lot and were replaced by the hadrasaurs, which were also pretty big, but they were generally bipedal, things like Iguanodon, and which was the first dinosaur to be described in the world. But these were bipeds, quite big, but with huge pavement-like teeth that they could use to grind up plant matter. Because also, other things were evolving. Flowering plants appeared in number during this period. So, uh, and these would have posed problems and opportunities for dinosaurs, as well as pollinating insects.
28:23 Speaker 02 I mean, when you hit, see documentaries about where people try to put CGI dinosaurs in modern landscapes, the biggest scourge of these landscapes is grass, because grass only evolved much later. So dinosaurs never ate grass, they ate ferns and, and, and other things. You know, maybe water lilies or magnolias, you know, the earliest flowering plant types to evolve, but grass was much later. So there was a huge amount of pollinating insects. And, and so the ecosystems were always changing, and so were the dinosaurs.
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30:38 Tristan Hughes? Henry, I love how you mentioned Di Gioranodon there. I've always got time for Di Gioranodon. It's thumb spikes, which I remember you saying in a previous conversation would have been great for hailing cabbies. But since cabbies hadn't been existed for millions of years, they weren't great for much else. But evidently, they were successful. We could go down so many different avenues from all you highlighted there, painting a picture of this ever-changing Jurassic world. I will ask about those biggest dinosaurs, though, because you mentioned how they're on four legs again. They're quadrupeds. Does this almost seem like, I don't think it's going backwards in evolution as such, but you mentioned the importance of bipedalism earlier for dinosaurs. And yet, when you see some of these dinosaurs get very big, it's like they abandon the bipedalist aspects
31:23 Tristan Hughes? and go back to going on all fours because they are that much heavier.
31:27 Speaker 02 I think what happens if you are an eater of vegetation and become quite large is that you have to eat an awful lot of vegetation to survive and vegetation takes a lot of digestion to release nutrients. So what happens when you see herbivores generally, they usually have large guts in which the vegetable matter ferments. We see this today. Cows have this four-chambered stomach in which the bits of the vegetation come up and are regurgitated and get ground up. And they're big and all the herbivores we see are big. If they're small, like rabbits, they have some other kind of fermentation, or they eat their own
32:11 Speaker 02 half-digested poo and digest it again. So it's the digestion and the dinosaurs, the herbivorous dinosaurs, solve this by becoming big. I mean amazingly big. And the question has often been, how is it that these dinosaurs became so big? When mammalian herbivores never got larger than maybe four meters, five meters at the shoulder, when you have The woolly mammoth, kind of. Yeah, and also these ancient rhinos, which hornless rhinos, they were even bigger, but they were absolutely nothing to Argentinosaurus, you know, and some of these things were maybe weighed fifty to seventy tons and were a hundred feet long. I mean, just gigantic. But the
32:54 Speaker 02 key is that dinosaurs were built in a completely different way. And the key to that was the way they breathed. Now, when you and I breathe in, you know, breathe in, breathe out, breathe in, breathe out. Failure to master this and reaching nirvana will be the least of your problems. But the thing is, it's not a very efficient way of gas exchange, because all the oxygen that comes in on your intake has to be replaced by the carbon dioxide coming out, and it all mixes up. So you'd never really get a full breath of fresh air each time you breathe. Now, but in dinosaurs, and also birds, which is
33:35 Speaker 02 Very, very crucial. They have a completely different way of gas exchange. Now, okay, they breathe in and breathe out through the same hole, but the lungs are connected to lots and lots of other air sacs that permeate the rest of the body, including the bones. So the bones of dinosaurs and also birds are very hollow and they're full of these air sacs. So dinosaurs were probably, they could grow bigger because they were mostly full of air. And this is good for heat exchange. When you are big and fat like me and not slim and svelte like you, heat exchange is rather difficult because as you get bigger, you have proportionally
34:20 Speaker 02 less surface area to your volume. In other words, your insides are much further from your outsides. So you have to have special ways of getting heat out. This is the limiting factor. Now, the biggest organ in the body that generates heat is the liver. That's the kind of biochemical factor. That's where all your digested food goes from your intestines. It goes to the liver, it gets broken down into all the nutrients you need and spread throughout the blood to the body. In a big dinosaur, a liver would be the size of a car. It would generate enormous amounts of heat. But the thing is, it had air sacs right next to it, so the liver was air-cooled. And rather than what happens in mammals, which is the
35:02 Speaker 02 heat goes into the bloodstream, which then has to go to the lungs to be converted from, you know, dissolved gases to gas in the air, which is quite inefficient. It would go straight into the air. So it was as if the liver was kind of on the outside. So it was because of this heat hand, air handling system that dinosaurs could grow so big without boiling themselves from the inside out. So that explains how dinosaurs grew so big. But also, they were marvels of engineering. If you look at the, any bone in a sauropod, particularly the backbone, it's, each bone is reduced to struts, which are the major load-bearing components. Any bone that wasn't.
35:45 Speaker 02 Load bearing basically evolved away. So even though these animals were huge, they were constructed very, very, very lightly. And if you look at one of these gigantic quadrupeds, it was less a reptile or a mammal than a gigantic quadrupedal flightless bird in the way it was structured. So all the, all the dinosaurs, carnivorous herbivorous were constructed in that way. This was, I think, this was basically worked out by a guy I know called Martin Sander, who wrote a fantastic paper on the heat handling of dinosaurs. But I think it contributed to their
36:28 Speaker 02 success. It was their amazing physiology. Now, this kind of air handling is found in birds, bits of it are found in certain lizards. So certainly in reptiles, there is this tendency to have this kind of one-way airflow system that doesn't happen in mammals at all.
36:48 Speaker 02 Mammals breathe. One thing you can tell about a mammal is the rib cage only goes halfway down the body. In a reptile, the rib cage goes all the way down. Because in the mammals, the halfway down rib cage is interrupted by the diaphragm, which is the muscle we use to help inflate and deflate our rib cage to allow this kind of breathing that we do.
37:09 Tristan Hughes? So interesting. And I'm glad we could focus on these, these bigger dinosaurs, Henry. But as you've highlighted there, you know, you've got those big Titan herbivores, and then you've got those big scary carnivores, you know, living side by side in this Jurassic world. But what about the smaller dinosaurs? Were there smaller omnivores that lived in the shadows of these, you know, massive dinosaurs of the Jurassic?
37:34 Speaker 02 Yes, there were. Among the kind of armored dinosaur branch of the dinosaurs were some fairly small creatures like Sitacosaurus, where parrot lizard that had crushing horny beaks, and more the Iguanodon type dinosaur. There was quite small herbivores that lived in the shadows of the larger ones. But the general tendency in the Jurassic certainly was to large size, although...
38:03 Speaker 02 Among the carnivorous dinosaurs, there was a lineage that made a virtue in smallness, partly associated with tree climbing. There were a number of creatures that as the Jurassic wore on, became, they adopted some of the characteristics we now say, say with birds, and we've discussed this before. They were the feathered dinosaurs.
38:25 Tristan Hughes? The feathered dinosaurs.
38:27 Speaker 02 The iconic feathered dinosaur is Archaeopteryx, which everyone thinks of as the first bird, which lived at the very end of the Jurassic period. Although it had perfectly good feathers and may have been capable of flight, it had a long bony reptilian tail, it had claws on its wings, it had a, it had a mouthful of teeth rather than a beak. Now, it's been associated as being the first bird because for a long time, it was the only one known and the reason why it was preserved in beautiful, beautiful, very fine grained limestone in what is now Bavaria. It's a lithographic limestone, it was used in printing, it was so fine grained.
39:08 Speaker 02 And the Solnhofen limestones of the Upper Jurassic of Bavaria have yielded all the known specimens of Archaeopteryx and other things too. Basically, they were, they'd fallen into a lake, which had very peaceful, quiet sedimentation and were swiftly buried and so are preserved intact with all the feathers. Now, for a long time Archaeopteryx was the only known fossil bird. The problem with birds is they have very fragile skeletons. I mean, I mentioned the hollow bones, I mean, when they die, they just shatter. So there were a few bits and pieces that nobody could really fit into anything.
39:47 Speaker 02 And there were some Upper Cretaceous birds from Kansas and Nebraska, which in the Upper Cretaceous were by the sea. It was, there was a huge seaway that went from north, in North America, from north to south at the time. And there was ichthyornis that looked like a seagull with teeth. And there was hesperornis, which was a big diving bird, which had already reduced its wings in a way like penguins or or something like that. So obviously, there was a lot going on that evolution hasn't hasn't preserved until the late nineties, when reports came through of fantastic, beautiful deposits in China,
40:31 Speaker 02 which combined, which were of lakes that had no oxygen, so no decay bacteria, and lots of volcanoes, so everything entombed in ash layers, which preserved birds with feathers, dinosaurs with feathers, mammals with furry coats and the remnants of their last meal. And you have to remember that mammalian paleontologists usually only look at teeth. They rarely get any more. So what we now know is that at the end of the Jurassic, there was quite a lot of evolution of feathery forms among very small dinosaurs. Archaeopteryx was just one. There were some very, very peculiar ones called scansoryopterygids that had feathers,
41:16 Speaker 02 but the wings were bat-like, made of membranes. There was a little dinosaur, and the scansoryopterygids, very long name, they could sit in the palm of your hand. They were the size of a thrush. And then there were dinosaurs called like Microraptor, that was more crow-sized, that had wings on its front legs and its back legs. So it was a kind of biplane. And there were loads and loads of these. What tend to happen, there were, there were three groups of dinosaurs that evolved around then and into the Cretaceous, the Dromosaurus, the Troodons, and the birds. Now, Dromosaurus include some of these very ferocious velociraptor-type things with a great big slashing claw on their hind legs.
41:59 Speaker 02 Troodons were similar, but they had very large brains and binocular vision. And people have thought that if they dinosaurs hadn't died out, spoiler at the end of the Cretaceous, they might have become of humanoid intelligence, all that's pretty speculative, of course. And then the birds, but because these things at the time were all kind of similar, it's quite hard to tease out. One from the other, but certainly there was a flurry of evolutionary activity at the end of the Jurassic period, going into the Cretaceous period, which produced these small feathered dinosaurs. Now, many din- other dinosaurs were feathered, even quite large ones. I mean, there's some very, very odd secondarily herbivorous carnivorous dinosaurs
42:41 Speaker 02 called therizinosaurs, which had tiny heads, huge bellies, immense meter-long claws on their forearms, and feathers. I I mean, they were about as fe- they were about as aerodynamic as a sack of spanners, but they had feathers. So it seems that the tendency to have what scientists called integumentary structures was, went way back. We now know that pterosaurs, the pterodactyls, which are close cousins of dinosaurs, they were fluffy on their bodies, although their wings were membranous. So there was a great deal of evolution. Now, when my son, who was, he's now twenty-seven, was at nursery school and absolutely obsessed
43:24 Speaker 02 with dinosaurs, used to whiz around the playground going, "I'm Archaeopteryx, the first bird! I'm Archaeopteryx, the first bird!" And then my wife used to go and collect him and try and get away very quickly, so she wasn't buttonholed by the nursery school teacher, who one day said, "He's not an Archaeopteryx, he's a little child." But now, of course, she'd say, "He's not the first bird, he's just another feathered dinosaur." Of course she would.
43:48 Tristan Hughes? Very naughty boy.
43:49 Speaker 02 Yeah, well, you know, things haven't changed.
43:53 Tristan Hughes? I must also ask, just because you said it in passing, yes, could you clarify also, you said with that species, primarily carnivorous, secondarily herbivore. Do you mean by that, that they are omnivores, they eat meat and plants, but they would primarily eat meat compared to plants?
44:08 Speaker 02 No, they they evolved from carnivorous forms.
44:11 Tristan Hughes? Ah, interesting.
44:12 Speaker 02 And then evolved back, evolved to be herbivores. These therizinosaurs, they had the shape generally of a big biped, but they were, they'd evolved to to eat vegetation. These long claws are pretty, I mean, they're meter long, the biggest claws in nature, the therizinosaur claws. Nobody knows what they would be used for. I painted a picture of, in a book I did a long time ago with a marvelous artist called Louis Ray, I did a lot of speculation and I said that theresinosos produced so much methane that if they were struck by lightning they'd explode, but I just like the image. I don't think there's any evidence for this.
44:50 Tristan Hughes? Exploding dinosaurs, so there we go. Well, we're getting towards the end of the Jurassic period, aren't we, Henry? And once again, time wise, when are we talking in the age of the dinosaurs?
44:59 Speaker 02 We're talking about 150 million years ago.
45:02 Tristan Hughes? Okay.
45:03 Speaker 02 There were other extinctions between the Triassic and the Jurassic. Now, the distinction between all these periods is usually made by changes in the rock record, and those changes in the rock record are usually related to some violent convulsion in the past. So there were, no, ranges of volcanic activity, the continents were still drifting apart. I mean, by the end of the Cretaceous, the continents were getting towards their present position, although India, Australia and Antarctica were still kind of joined. Antarctica was beginning to move southwards. India was separated and was moving towards Asia, where it would
45:44 Speaker 02 eventually collide and produce the Himalayas. Madagascar was separate in the Cretaceous, which led to an incredible radiation of dinosaurs only found in Madagascar. So we were beginning to get in the Cretaceous that endemism. There were dinosaurs only known from Western North America and China, because Western North America was separated from Eastern North America by the Neobrara Seaway, but it was joined through Alaska to Eastern Asia. And there was another seaway through Siberia, so Europe was different. But apart from these kind of changing sea levels, if you can kind of half close your eyes, the Cretaceous distribution of the continents was beginning to look much like our own. There's still, the Antarctica
46:29 Speaker 02 hadn't drifted over the South Pole, which was important, because when Antarctica drifted over the South Pole, that was much later, after the dinosaurs had become extinct, we started to go. Into the kind of ice ages in which we live now, but the Cretaceous world was very climatically stable. There were, it was pretty much as warm as it was in the far north, as it was in the far south, as it was in the middle. So we didn't, there wasn't a great deal of stormy weather. It was very calm. It was kind, the earth was kind of taking a break. It was kind of a bit sleepy. There weren't even many reversals of magnetic fields which often happen. So there were dinosaurs
47:08 Speaker 02 living in the north slope of Alaska. Now, even though it was quite warm, we still got six months of complete darkness. I mean, it still was quite warm. And there were dinosaurs living in Antarctica, which was covered in forests at the time. There were dinosaurs that were endemic to particular areas. So the dinosaur world became very fragmented and very much more diverse in the Cretaceous than it had been in the Jurassic. Although the Titanosaurus, sawrepos were still going, a lot of the herbivore world was replaced by the iguanodon type hadrosaurs, some of which lived in huge herds and had these immense crests and ornamentation, a bit like herds of antelopes
47:53 Speaker 02 or something today. The carnivores became very varied. There were big ones, little ones, and huge ones, like the, at the very end of the Cretaceous, our friend Tyrannosaurus rex, which lived by battling huge armored dinosaurs, such as Triceratops and Ankylosaurus. Tyrannosaurus rex, everyone's favourite, probably except my wife, she prefers Triceratops. But it's a good, good reason. It was five tonnes of muscle and bone and teeth that had the shape and consistency of bananas, if bananas were made of carbon steel. And it could crush right through bone. And we
48:36 Speaker 02 know this because we even have Tyrannosaur poo, and Tyrannosaur poo fossilized as well because it's mostly made of crushed bone. So nobody really knows if it was a scavenger or it Actually eat live prey, probably a bit of both. But nothing like it has been seen before or since. The only bigger carnivorous creatures on earth were aquatic ones, the pterosaurs. Which lived in the Cretaceous period and they would have made Tyrannosaurus look like a big girl's blouse. I mean, they were just, you know, ferocious. Of course, by the end of the Cretaceous, the ichthyosaurs had become extinct. They were really, they became extinct in the middle of the Cretaceous.
49:19 Speaker 02 But we still had in the marine realm gigantic sea serpents, you know, the mosasaurus that were gigantic sea lizards closely related to komodo dragons. Only much bigger and with flippers and the plesiosaurs, which look like snakes threading through turtles and of course the pterosaurs. These immense, short-necked, huge-headed plesiosaurs that were the primary predators of the sea. Alongside turtles as big as Volkswagen Beetles and ammonites, these mollusks the size of truck tires. So it was, there was a big stuff in the sea in the, in the, in the late Cretaceous as well as on the land and in the air too. Now, because the climate was quite mild, there wasn't too much storm and wind.
50:03 Speaker 02 These pterosaurs could evolve huge sizes, the biggest aeroplanes that just soared. They didn't need to flap, they soared. And they were some of the latest pterosaurs. They were so big, they didn't fly much at all. They just walked around on the ground with their legs. And their wrists and their wings sticking up and their huge necks looking like gigantic animated marquise. And some of the very last ones could have stood eye to eye with a giraffe.
50:28 Tristan Hughes? Is this the one which is like Quetzalcoatlus, the Aztec serpent god of the sky?
50:32 Speaker 02 Quetzalcoatlus as one, but there were even bigger ones called ajdar kids. I can't remember if Quetzalcoatlus is an ajdar kid, but these very, there was one called Aramborgyama. I think they're known from the Middle East. These very, very large ones. Nobody knows if they could fly, but if they could fly, they just needed to open those enormous wings. Into a slight breeze and they'd take off. But they could only live when the climate was fairly gentle. At the end of the Cretaceous, it got more stormy and they would have just been blown out of the sky like umbrellas. And so, towards the end of the Cretaceous was the most amazing world of enormous carnivores
51:14 Speaker 02 on land and sea, enormous and middle-sized herbivores on land, but also tiny ones. Because in the Cretaceous, the first true birds appeared. And by the end of the Cretaceous, there were birds kind of of modern aspect. At the end of the Cretaceous, there were the ancestors of ducks and chickens. They were what's called transitional shorebirds. They lived then. And some signs of birds of a more modern aspect had begun to appear, but they didn't start their flourish until after the dinosaurs had died out.
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53:30 Tristan Hughes? You've given a wonderful overview there of the great variety of animals in the Cretaceous world, and you actually preempted a couple of my questions, which was to look at the world, you know, these animals in the sea and also these great animals in the air as well. I'd actually like to ask one other small question about animals in this age, which is you mentioned in passing much earlier, how giant salamanders from an ancient, you know, a much earlier age had survived in like the Arctic and Antarctic areas. Is that still the case in the Cretaceous? Do you still have giant salamanders and the like at this time?
54:05 Speaker 02 Yes, there were giant salamanders in the Cretaceous. They were the very last ones. I mean, there were ones, there were great big ones in Australia called Culisucus, great big crocodile-like amphibians, but they were the last of a long lineage. They were beginning to be replaced by reallyo trulyo crocodiles by the, by the end of the Cretaceous, because the crocodiles had kept evolving as well. There were some absolutely gigantic crocodiles in the Cretaceous, one called Phobosuchus that was just enormous. In the Cretaceous, there was also a gigantic snake in the tropical jungles of Colombia called Titanoboa, which was the size of a bus. And so there were also lots of mammals as well. And although
54:50 Speaker 02 mammals tend to be very nocturnal and quite small, there were at least 20 different kinds, major groups of mammals that lived and died before the dinosaurs became extinct. Some of the earliest ones, the Haramidae, were gliding mammals, and they were probably in the trees gliding about before birds originated. There were some mammals that were like beavers, Castorocauda, had a, was a very primitive mammal, but it had a very flattened beaver-like tail. And there were, there was a badger-like creature called Repanomamus that actually ate dinosaur eggs and babies. So it wasn't all one way. Now, a lot of these mammals would have laid eggs, like the current-
55:34 Speaker 02 Monotremes like the platypus fellows today, the platypus and its rated echidna are the descendants of a very ancient triatic lineage of mammals that survives to the present day. But in the Jurassic and Cretaceous mammals were also evolving and they evolved the first marsupials like kangaroos and wombats originated in the during the time of the dinosaurs and they lived around the southern continents, South America and Australia and even at the time they invaded North America and opossums which are marsupials raid suburban trashcans in America to this day. But they were also the earliest mammals that are placental mammals that would bear live young.
56:18 Speaker 02 These originated in the time of the dinosaurs in the early Cretaceous maybe, but at the time you wouldn't have been able to tell the difference just by looking at them. I mean, they were all much of a much as small, furry, largely nocturnal, lived on insectivores, plants, eggs, eggs of birds, eggs of dinosaurs, eggs of each other and other things they could get their little sharp pointy teeth into. But they were evolving as well. And as I say, there were many different kinds of mammals that came and went before the extinction of the dinosaurs.
56:49 Tristan Hughes? Could some dinosaurs also swim?
56:52 Speaker 02 This is a huge bone, dare I say it, of contention. Dinosaurs were very, very successful on land, but it's it's almost certainly the case that some dinosaurs could certainly paddle. There are, there's a group of dinosaurs called spinosaurus, which had very long crocodile-like heads with very long crocodile-like teeth which look for all the world like fish eating creatures, which tend to have long, long snouts and lots of long pointy teeth. And there is a very famous spinosaurus, Spinosaurus aegyptiacus, that lived in Egypt and North Africa that.
57:32 Speaker 02 Most of the original remains were destroyed in the war, they were in in in Germany. But quite a few have been found since, and a case has been made that they could swim. They had big swishy tails, you know, vertically extended up and down tails. They had crocodile like jaws and they they might well have swam. There were related ones called suco mimus, which means crocodile mimic, which may have swam. But you mentioned that on internet forum, you know, just put a hard hat on and hide underground, really. There's a lot of debate about whether spinosaurus could swim. But I think dinosaurs could have swam in a general way.
58:13 Speaker 02 It used to be thought that these giant sauropods were so big and heavy, they couldn't support their weight on land and had to live in the water. Certainly when I was a kid, that was the prevailing view. And there's a chap called Brian Ford, who wrote a book saying too heavy to walk or something that that makes this view. But I have to say, these views are now no longer current. They they've been, shall I say, blown out of the water by other evidence from modeling their weight distribution and because sauropods weren't like elephants, they were like birds. So they're very lightly constructed, they couldn't walk on land and to do with the sediment in which they were were found.
58:54 Speaker 02 Also, we now know that the metabolism of dinosaurs was much greater than we thought. They weren't lumbering great reptiles, they were very alert, busy creatures. And they were quite capable of of living and surviving on on land. But there is no reason why some of them might not have swum um in the way that mammals that don't usually swim do swim, like elephants and other things. They could have migrated between various islands by swimming. This is not impossible. I mean, if you look at a skeleton of a golden retriever, you wouldn't know that it was a capable swimmer. If you look at a skeleton of a goat, you wouldn't believe that they can climb trees. So so it's very hard when you just look at a skeleton to dismiss the use of occasional lifestyle choices like swimming.
59:41 Tristan Hughes? So let's move on to the late Cretaceous, and you've already mentioned, you know, those well-known dinosaurs like the Tyrannosaurus rex, the Triceratops, Ankylosaurus with this massive club, isn't it? And I think like, how could any ferocious carnivore try and take down a massive armored plated dinosaur like an Ankylosaurus? It's surely just a death wish. Those animals, those dinosaurs feel impregnable.
1:00:04 Speaker 02 You know, if there is an animal that evolves, there's another animal that evolved to eat it. Tyrannosaurus was very big and not only had enormous teeth and neck muscles that could penetrate bone, it had enormous hind legs that could pin anything down, maybe turn it over and scrape it out, use the Ankylosaurus as a kind of bowl of ramen noodles, I don't know. But it seems to have been a specialist in eating these armored dinosaurs. Certainly Triceratops, there are Triceratops fossils that seem to have puncture wounds from large carnivorous dinosaurs in their bony neck frills. And there are, I think, large theropod dinosaurs
1:00:44 Speaker 02 with wounds that might suggest they'd been in battle with an armored dinosaur or perhaps another large carnivorous dinosaur. So these things were tough and these things were tough and ruthless. They certainly weren't rough and toothless. So they would have been specialised for this sort of thing. It's kind of an arms race as herbivores evolved stronger defences against carnivores and carnivores become more fierce and powerful to tackle the herbivores.
1:01:13 Tristan Hughes? And were real-life velociraptors as ferocious as they've been depicted in the media today?
1:01:22 Speaker 02 Probably. There was always a kind of, in the ecosystems of the dinosaurs, for the small, fast-moving carnivorous dinosaur. I mean, back in the Triassic, there were these things called Compsognathus, which was small, fast-moving dinosaurs that would have etched small things like insects and small mammals and frogs and things. Velociraptor was about the size of a turkey or a chicken. The ones that you see in Jurassic Park, now that was kind of fortuitous because the Velociraptors in Jurassic Park, still a wonderful film, I think, after all these years. They were called velociraptors, but they're actually much bigger than the real velociraptors. But as it would have it, some people found a velociraptor like dinosaur in Utah, which
1:02:07 Speaker 02 became called Utah Raptor, that was the size of the velociraptors in the film. These dinosaurs, these carnivorous dinosaurs, of course, a lot of it's very speculative, but there's no reason to think they weren't highly intelligent pack hunting creatures like hunting dogs or hyenas. And they would have had a kind of intelligence and they could have worked together to to hunt. And also, these these particular dinosaurs, called the dronosaurs, had on their second digit of their hind limb, this scythe-like claw that could be used to disembowel something. Certainly, they would be more than you'd need to scratch your nose. They could have been formidable weapons.
1:02:49 Speaker 02 And they were very active and there are reconstructions of them jumping on the backs of creatures and slashing with their claws. Maybe they, in a pack, weakened their prey by a thousand cuts, basically, which is what happens sometimes in predators and prey today. So I don't think there is any reason why velociraptor-like creatures weren't every bit as fierce as they are portrayed. I don't think they spent their time sitting around having cupware parties.
1:03:20 Tristan Hughes? I've got so many more questions. I'm gonna sneak in a couple more because this is such a fun chat and I know everyone listening is loving it. Henry, I will ask the classic old question, but I feel it's important with this topic. And then I'll share mine as well. You mentioned how Mrs. G's favourite dinosaur is Triceratops. I've asked people around the office, what is their favourite dinosaur? We've got some interesting ones, like a Pachycephalosaurus, Brontosaurus was quite a popular one, the big one, and Stegosaurus as well. Not many T. rexes, actually, but what is your favourite dinosaur?
1:03:53 Speaker 02 Well, I have to say it's Triceratops because you know, happy wife is happy life.
1:03:58 Tristan Hughes? I was, I thought you'd say one of the feathered dinosaurs, honestly, Henry. I thought you'd go to that.
1:04:03 Speaker 02 Well, yes, maybe if my wife's not listening, I'd say something like Microraptor.
1:04:07 Tristan Hughes? Okay, okay. And I will always go with a Guanadon because.
1:04:11 Speaker 02 Well, I know, I know from our previous chats, you have a family connection. You are not actually related to an iguanodon, but I think you're related to the people who discovered it, aren't you?
1:04:22 Tristan Hughes? You know, like, like your son at kindergarten, exactly saying, I'm an archaeopter. So I was saying, I'm an iguanodon everywhere and saying, but no, I'll always go to about, yes, I have a very, very distant relation to the mantles. Which is a lovely one. But Henry, come on then, let's go to the big climax. We have spoiled it a little, but I think most people do know what happens to the dinosaurs or get a sense that they're not around today. So there is an extinction. Talk us through what happens in the late Cretaceous period. What do we think happens?
1:04:51 Speaker 02 The extinction of the dinosaurs for a long time was a non-question. And the reason why is that people thought that creatures evolved, they flourished and they died as a kind of a natural order of things. They fretted and strutted on their stage and then made their various exits. And the end of the dinosaurs just came, it was going to happen anyway. But it seems that was not the case. People came up with all sorts of wacky ideas for why dinosaurs became extinct. They got so big they couldn't move, or they died of arthritis, or their eggs got so thick that the baby dinosaurs couldn't hatch. Or the eggs got so thin that they died before they could hatch.
1:05:34 Speaker 02 Or they died of hay fever from those new fangled flowering plants. Or they died from indigestion from those new fangled flowering plants. Or they forgot about having sex, or they just got bored. And this is, there's even a word for this, it's called paleo Velchmetz. After, after a hundred and sixty million years as the lords of creation, they ran out of things to do and just died. Professor Mike Benton, who's now in Bristol, and I believe you know him, he's the expert.
1:06:04 Tristan Hughes? Absolute legend.
1:06:04 Speaker 02 Great dying. He actually wrote a paper summarizing all the many, many hypotheses about dinosaurs becoming extinct. And it's a, it's a, if you can look it up, it's a, it's a great read. But one of the more outrageous ideas at the time was that the earth was struck by a gigantic asteroid that wiped out a lot of life. And of course, everyone who proved this idea as completely ridiculous compared with Paleovelt Schmetz or any of the others. But that was the idea that turned out to be true. It seems that at the end of the Cretaceous period, the sediment, the layer in the rocks that separates the Cretaceous period from the overlying rocks
1:06:46 Speaker 02 is very thin and has a concentration of a metal called iridium that's very rare on earth, which is actually quite common in certain asteroids. And this was found in Italy, in Denmark, in America, I think in New Zealand, so all around the world. And a couple of physicists, Luis and Walter Alvarez, who are father and son team of physicists, they worked out the sedimentation rate of this iridium and showed it would have happened very quickly. Also, in around the Gulf of Mexico are what are called tsunami beds.
1:07:24 Speaker 02 At the end of the Cretaceous, the rocks are all kind of jumbled up, looking like there was a immense, immense disturbance, like a tsunami. And eventually, the smoking gun was found underneath the Yucatan Peninsula is a circular structure that was originally discovered by Mexican oil geologists. It was a part of the state oil company of Mexico. They found this circular structure about 160 kilometres wide. And that's since been buried by other sediment. But that seems to have been the place where an asteroid 10 to 20 kilometres in diameter, hit the earth.
1:08:08 Speaker 02 And it would have hit the earth, it would have given it a great old smack, and it would have gone right through the crust. And now, a lot of the, a lot of the sediments it penetrated were full of sulfates. It was gypsum, you know, from an ancient seabed where it had all evaporated. And that produced a lot of sulfur dioxide into the atmosphere that poisoned the seas. The, the smoke would have basically
1:08:32 Speaker 02 hid the entire earth from the sun for years and years. The actual blast wave of the impact would have been felt for at least a thousand kilometres around. All the trees would have been flattened and there'd been widespread wildfires. Well, not surprisingly, this had a big effect on all the wildlife. Now, all the dinosaurs that weren't birds disappeared. There have been claims that some survived, but none of these claims has been substantiated. All the big marine reptiles, the mosasaurs, the pleseasaws, uh, so on, they, they, they died out as well, as well as the big truck tyre sized ammonites, they died out as well.
1:09:13 Speaker 02 And quite a lot of other things died out as well. Quite a lot of these groups of mammals died out, all except four of the twenty or so died out. And quite a lot of plants. So it had a big effect on the ecosystem. But of course, everyone remembers the extinction of, of the dinosaurs, or what we now call the non-avian dinosaurs, particularly because they were the kind of poster childs of the Cretaceous. They all disappeared. Now, like all overnight sensations, this took a long time in the telling. It now appears that the origins of the asteroid that wiped out
1:09:54 Speaker 02 the dinosaurs was in a collision in the inner solar system between two other asteroids about a hundred and sixty million years ago. So in the Upper Jurassic, so everything was evolving on earth unaware that its card had been marked. The, this collision produced a magazine of a thousand fragments, which started migrating into the inner solar system. And one of these was the asteroid that wiped out the dinosaurs.
1:10:22 Tristan Hughes? How can we know this? That is insane.
1:10:24 Speaker 02 Well, just from very, very patient examination of rocks, we know that the, uh, and orbit, orbital parameters of asteroids. So the dinosaurs were, you know, their, their appointment with, with destiny, or as one comedian said when I saw him on stage, Des Tiny, was marked a long time ago, before the dinosaurs became extinct. Now, of course, we wonder whether dinosaurs would have become extinct anyway. I think they probably would eventually.
1:10:53 Tristan Hughes? You preempted what my next question was going to be. Would dinosaurs have gone extinct if there had not been an asteroid?
1:10:59 Speaker 02 Yes, eventually, because that's what all species would do, but they wouldn't have done all at once. They'd have done it one at a time and in different ways. And the world might have been completely different had the dinosaurs not become extinct. I am proud to have coined the Carenina principle, which says that all happy thriving species are the same, but all species in danger of extinction die in their own way. So that's a literary reference there, kids. So, but they, but who knows what might have happened. There are, there's been science fiction written that the dinosaurs lived until the present day with, with humans living in a kind of subservient niche environment. So who knows
1:11:42 Speaker 02 what would have happened. But it's quite interesting that of the big five mass extinctions of the last 500 million years, the end Cretaceous extinction is the only one certainly known to have been caused, as far as we know, by an asteroid. There was a lot of volcanism at the time at the end Cretaceous. There was loads of floods, but battles in India that could cause of a certain amount of disruption. So if they just happened without the asteroid, there may have been some kind of extinction, but that's kind of been overprinted, as it were, by the, by the asteroid. So we don't know what would have happened if the asteroid had missed.
1:12:21 Tristan Hughes? Well, there we go. Another of those big what if moments of, well, prehistory and the story of the dinosaurs. And the dinosaur extinction, Henry, will lead, I mean, isn't it first to the dominance of birds for a small part, for a small period of time, and then ultimately the rise of mammals?
1:12:36 Speaker 02 Hmm. Now, just after the end of the Cretaceous, of course, after any kind of mass extinction, there's a kind of breathing space in which, for a while, all kinds of weird things happen. The mammals probably breathing with relief that the dinosaurs had gone away. When they put their heads out of their burrows, they were bitten off by these gigantic birds, these terror birds.
1:12:57 Tristan Hughes? Terror birds.
1:12:58 Speaker 02 The terror birds. And they had heads the size of horses' heads and they enormous beaks. And they were flightless birds. They weren't related to ostriches or the other flightless birds. They were, they were related to cranes and, and rails. They were that kind of bird. But these came and went. And then the mammals, well, the birds evolved explosively into most of the modern birds, the kind of group of birds called Neo-aves.
1:13:26 Speaker 02 Basically is all the modern birds that aren't ducks, geese and waterfowl or ostriches or rattites, and they evolved explosively at the end, after the end Cretaceous into all the birds you see today. And there's a lot of scientific debate about how fast it was and which birds evolved before what and whether some of them, some of them might have evolved earlier in the Cretaceous. I mean, there's a, there's a paleontologist called Tom Stidham, and he found this fossil which looked like a parrot beak. And he would show it round to people and say, what do you think this was? And they'd say, it's the parrot beak. And then they would say, how old is it? And he'd say, Cretaceous. And
1:14:07 Speaker 02 they'd say, no, it's not a parrot. And we published this, this in Nature. I was an editor at the time. And I also wrote the press release, which I enjoyed doing at the time. I, I still dream of writing, I love writing press release. So the managing editor came over to me and said, lay off the Monty Python references. So I called the title of the press release Sketch of Dead Parrot. And I didn't say it had shuffled off its mortal coil or gone to join the choir invisible. So I played it absolutely straight. But at the end, I wrote, the beauty of the plumage of this species is not recorded. Now it's thought that this wasn't a dead parrot. It was a kind of a small dinosaur with a beak, because some herbivorous dinosaurs had a beak. Anyway, birds, but also mammals. There were four
1:14:52 Speaker 02 kinds of mammals, four groups of mammals that survived the extinction. One were the monotremes, the egg laying mammals that just kept on trogging along in their own way. The other was the marsupials, who had a big flourish in South America, which was an island continent for a long time. And they had gigantic saber tooth marsupials that looked like saber toothed eagles that lived in South America. So, but nowadays, they, they live in Australia, where you have kangaroos and wombats and koalas. But they've been quite successful for a long time because of their strange mode of reproduction, which makes it easy for them to colonize very arid, arid habitats. And then they are, then there was a group called the multituberculates, which actually, they were
1:15:35 Speaker 02 In the Cretaceous and they survived till the Eocene, so about ten million years after the dinosaurs began extinct. And they were very rodent like, they had strange multi-tuberculate teeth, they were teeth with lots of tubercles on. And they had long incisors, so they were much like rodents. And they died out in the Eocene, probably in competition with real rodents that evolved by then. And rodents were part of the placental mammals, which includes you and me and most mammals that we know of. But in the first flush, the first few million years of placental mammal evolution after the end of the dinosaurs.
1:16:15 Speaker 02 There were some placental mammals that got very big very quickly and the first flush of mammals, they weren't very clear on their life goals. Some of these strange early ungulates, they had hooves but enormous teeth. There was this creature called Andrew's Arkus. Which was a gigantic terror pig. I mean, you wouldn't want to, you know, call it a warthog to its face. But there were these lumbering creatures called Panthothears and Dinosaurites, which are not closely related to any modern mammal. And they used to be called amblypods. And I remember being an undergraduate, learning about these. And I was charmed. And after the day I went to a telephone box, because that's all we had in those days.
1:16:54 Speaker 02 And I phoned my mum and told them about these creatures called amblypods. And she said, that's nice, dear. You can just imagine them ambling their pods, can't you? So anyway, after the first few million years, the earth went through one of its convulsions. And there was a period in the Eocene where the, the, the earth was basically a jungle from pole to pole. It was a, a, a hothouse planet. It was called the Paleo E O C, Paleocene Eocene Thermal Maximum. And after that, the earth started to get cooler. When Antarctica moved over the South Pole, it got cooler still. And that replaced a lot of the jungles with grasslands. And it was then that the placental mammals that we know today.
1:17:37 Speaker 02 Evolved, the old antique ungulates and antique carnivores became extinct to replace, be replaced by.
1:17:45 Speaker 02 The ancestors of dogs, cats, lions and tigers, cows and horses. Also, there was one of the biggest evolutionary transitions in the whole of of evolution, which is these ungulate-like creatures that look like dogs evolved into whales in eight million years. And which still is utterly remarkable. There were all sorts of amazing weird mammals that have lived and died in the subsequent fifty, sixty million years since the dinosaurs died out, until we get to our wonderful world today.
1:18:20 Tristan Hughes? Well, Henry, you mentioned so many things there, terror birds, saber-doofe cats, whales, you know, all creatures to be covered in future episodes that have their own great stories to tell. I also love the fact that, yes, between the extinction of the dinosaurs sixty six million years ago or so and today is a smaller round of time than between sixty six million years ago and where we started our chat over two hundred million years ago. So that also puts into perspective how long the dinosaur age was. Could ask so many more questions, but I must wrap up now. Henry, last but certainly not least, you have written a book in the last few years, which does cover the story of the dinosaurs and life before the dinosaurs and after. It is called?
1:19:02 Speaker 02 It is called A Very Short History of Life on Earth, which is available in all good bookshops and on audiobook and Kindle and so on. But I've written a couple of other books since then. One is about human extinction. It's called The Decline and Fall of the Human Empire. But I can now announce to you that I've got another book coming out in February. I'm going to show you it.
1:19:24 Tristan Hughes? Have we got the scoop?
1:19:25 Speaker 02 You may well have the scoop. It's called The Wonder of Life on Earth, and it's basically for kids. It's like when I wrote the the Very Short History of Life on Earth, people said it hasn't got any pictures. So I was approached by a publisher of children's books called Two Hoots that are an imprint of my current publisher. And they said, write a children's book. So I completely rewrote the text and a wonderful illustrator. In the Philippines called Roxanne Manikins has illustrated it. And here's some weird thing. And it's coming out in February, February the 5th. It will be published and you can preorder it now. It's called The Wonder of Life on Earth.
1:20:11 Speaker 02 Unfortunately, it can't come out for Christmas, but it can come out for Christmas after. So it's very nice. Buy it for your kids, nieces, nephews and all the dino tops in your life.
1:20:24 Tristan Hughes? Henry, as always, such a pleasure. It just goes to me to say thank you so much for taking the time to come back on the podcast.
1:20:29 Speaker 02 Very welcome. It's always a blast and I always look forward to another, another visit to History Hit.
1:20:39 Tristan Hughes? Well, there you go. There was the one, the only Dr. Henry G returning to the show to talk you through the age of dinosaurs. I really do hope you enjoyed the episode. Thank you so much for listening. Now, if you did enjoy this episode, please make sure that you are following the ancients on Spotify or wherever you get your podcasts. That really helps us and you'd be doing us a big favour. If you'd also be kind enough to leave us a lovely rating as well, well, we'd really appreciate that. Now, don't forget, you can also sign up to History Hit for hundreds of hours of original documentaries with a new release every week. Sign up at historyhit.com/subscribe. That's all from me. I'll see you in the next episode.
1:21:29 Speaker 01 Hey, we're Nick and Jack, hosts of the best one yet. Behind every episode, there's research, emails, spreadsheets and our shared Google Doc, the headline hammer. With Google Workspace with Gemini, Google's AI is built right into the premium versions of tools we already use, like Gmail, Docs and Sheets. No new tools or extra logins, just personalised AI for the way we work. That means less time on the work around the work and more time finding the stories worth talking about. Get AI tools for work. Upgrade to Google Workspace with Gemini at goo.gle/workspacewithgemini. That's goo.gle/workspacewithgemini.
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