The rise and fall of the dinosaurs
In his book, The Rise and Fall of the Dinosaurs palaeontologist Steve Brusatte describes the conditions which allowed dinosaurs to flourish and dominate the planet for so long and then face sudden extinction. Along the way, a period of 150 million years, they diversified with some growing to enormous size. Some developed feathers not for flight initially, more likely for insulation. Some smaller dinosaurs survived the mass extinction that took 95% of species. Later they learned to fly, evolving into today’s birds. And the void when dinosaurs became extinct allowed mammals to flourish, leading to today’s species, including Homo sapiens.
Robyn Williams: The Science Show on RN, and so to the ancestors of those birds and the author of a book that has been in the top 10 of the London Times bestseller list for a long time, The Rise and Fall of Dinosaurs: The Untold Story of a Lost World.
Steve Brusatte is a Professor of Palaeontology at the University of Edinburgh, and he has been finding fossils in China, Poland and in North America. But let's start just before those terrible lizards first turned up.
What was the planet like 253 million years ago?
Steve Brusatte: This would have been right at the end of the Permian period, these were the last few seconds on the clock at the end of the Permian period. This was a time when all of the continents were smashed together into one, the supercontinent Pangaea stretched from the North Pole to the South Pole surrounded by a single global ocean. It was quite hot and arid in the middle of that supercontinent, big deserts throughout. But there was quite a lot of living things on the world then. There were lots of species of reptiles, there were lots of amphibians. There were some of the antecedents of mammals, some of our distant ancestors, these big reptilian-looking proto-mammals, and some of these things are at the top of the food chain. Big predators, big plant eaters, things that were much bigger than cows, much bigger than giraffes. And that's how the world stood 253 million years ago, right as the Permian period was about to come to an end and the whole history of life would be reset pretty quickly and very dramatically.
Robyn Williams: And then 252 million years ago, tell us, what then?
Steve Brusatte: Then something happened, the earth started to rumble a little bit. This was deep in the earth. The animals on the surface couldn't really feel it, but what was rumbling were big currents of magma deep in the earth. And there was a hot spot of magma underneath what is now Siberia, and this snaked up to the surface and it erupted. But it didn't erupt in just a normal volcano. This wasn't what is happening in Hawaii now, this wasn't Mt St Helens or Pinatubo blowing its top, this was a super-volcano.
Huge fissures in the earth opened up, maybe even Grand Canyon-sized fissures, and tsunamis of lava flowed out of those cracks in the crust. And you had a huge part of Siberia covered in lava, which of course scarred the landscape and it killed anything in the vicinity of that Siberian area, but it also had global effects because coming up with the lava was a whole bunch of nasty stuff, carbon dioxide, methane, sulphur dioxide, a lot of poisonous gases that went into the atmosphere and led to a runaway global warming event, and so that changed the world and that caused a mass extinction, that caused the biggest mass extinction in the whole history of the Earth. This was the closest that life had ever come to going completely extinct. Up to 95% of all species died out because of those volcanoes and the global warming that came afterwards. This was the end Permian extinction and it was a terrible, terrible time to be alive.
Robyn Williams: And it doesn't seem to be the sort of stage where you'd expect one of the most successful groups of animals, yes successful, because some people think they are weird crocs that came and went in a bit of a flurry, but they stayed for a long time, were wonderfully agile, varied. How did they manage somehow to get born or evolve out of that really terrible scene you describe? It seems most unlikely.
Steve Brusatte: It does, but believe it or not the age of dinosaurs only happened because of that extinction. That extinction made it possible for dinosaurs to rise up. Most things that were alive at that time couldn't cope, and most things died, but a few stragglers did make it through and there were a few reptiles that made it. And then on the other side of that extinction, as the volcanoes stopped, as the world started to heal, as ecosystems recovered, those survivors now had pretty much a wide open world all to themselves, a new world to conquer, and they did, and very quickly these reptiles diversified into a bunch of new species, including the very first representatives of a lot of the most familiar animals in today's world. The first turtles, the first lizards, the first crocodiles, the first mammals, and these very first dinosaur ancestors.
And so on the other side of this Permian period after the extinction is over, we are now in the next period of geological time, what's called the Triassic period, and this is the time of rebirth and this is the time when those surviving reptiles, some of them turned into these first dinosaurs. But those first dinosaurs, and they are very close relatives, they were not like the dinosaurs that we know. They didn't look like T. Rex, they didn't look like Brontosaurus, they didn't shake the earth as they walked. These were humble animals, they were small animals, they were just the size of house cats, they were gangly, they were awkward looking, they had long legs, these stilty little legs and they would run around on all fours. And there were not very many of them, they were vastly outnumbered, overshadowed by a lot of the amphibians and other reptiles, and even some of the early mammal relatives of the day. It was from those very anonymous origins that the great dinosaur empire would eventually stem from.
Robyn Williams: And were some of them Polish by any chance?
Steve Brusatte: Yes, absolutely. So in the book I jump in to tell the story about how my colleagues and I found some of the first traces of these first dinosaur ancestors in the very earliest Triassic and we found these fossils in Poland. And they are not skeletons, they're not bones, but they are footprints, they are the footprints and the hand prints that these little housecat-size creatures left behind, and also footprints and hand prints that were left behind by the bigger and more common animals of the day that were also blossoming in this post-extinction world.
Really my Polish colleague, Grzegorz Nied?wiedzki who grew up in this area in central Poland, he started looking for fossils when he was very young, he found some of these tracks when he was still a teenager. These tracks are tiny, they are just a few centimetres long and the footprints are a little bit bigger than the hand prints. But we can see from these tracks features that are shared with dinosaurs. We can see that there's just three main toes on the foot, for instance, so if you ever look at the foot of a T Rex, let's say, or the foot of a chicken today, there's those three main toes, and we see those in these tracks. They were walking upright, they had their legs and their arms underneath their body because their trackways are really narrow, and that's a hallmark of dinosaurs as well.
And so these tracks were made just about 250- to 252 million years ago, within the first million or two years after those volcanoes. So these were some of the very first animals that were staking their claim in this new world. And after many tens of millions of years of additional evolution they would produce the dinosaurs.
Robyn Williams: Yes, but you see, this new world, one imagines that things have settled down and there was lots of lush vegetation and it was all very cool. The picture you paint, because it's still Pangaea, and it seems as foul as it was, as you described before, hot, steamy, terrible stuff.
Steve Brusatte: It was not a very safe or nice place to call home. The volcanoes had stopped erupting. So the big catastrophe was over, but when those volcanoes stopped you still did have Pangaea, this one big continent was still there, and it still had really nasty weather and it still had deserts in the interior of that supercontinent. If you were in the middle of Pangaea you were something like tens of thousands of kilometres from the closest coast, so these were desert wastelands. And you also had really bad storms at that time, what geologists call mega-monsoons. So if you think about the monsoons today that affect Southeast Asia for instance and think about hyper-powered monsoons, and that's what you had back then just because the weather was so violent on that supercontinent, and what that meant was the very first dinosaurs didn't live everywhere. Even though it was one landmass, they couldn't just go wherever they wanted because there were different climate zones. And those first dinosaurs couldn't really handle the deserts and they couldn't really handle the superhumid tropical areas. So they were restricted to just a few parts of that supercontinent. So not only were they small, not only were they outnumbered by the amphibians and the reptiles of the day, but they were also only living in a few places. It was really a very humble start to the time of dinosaurs.
Robyn Williams: But then of course you had the triumph, you had the spread into new areas and a rate of evolution amongst all sorts of different types producing what is one of the most successful sorts of animal, lots of them, different varieties all over the place, that the world has ever seen. And this is the point you try to make, not that they were a strange and weird sideline that existed for a brief period, but they were really in many ways the example of evolution at its best and finest and most powerful.
Steve Brusatte: That's how I see it. I think it's so unfortunate that the word 'dinosaur' is so often used as an insult, it's hurled at politicians and out of touch celebrities and washed up movie stars and what have you, but it really should be the opposite. Dinosaurs should be a token of success because dinosaurs were an empire. And yes, they had a humble start, but once they seize power and they spread around the world they started to evolve into enormous sizes and they started to diversify, and you had plant eaters and meat eaters and you had fast running, you had dinosaurs living in the trees, you had burrowing dinosaurs. The fact that these biggest longneck dinosaurs were the size of Boeing 737s is just a fact that continues to blow me away, that nature could produce something of that size…
Robyn Williams: Why were they big? What's the point of being big? You've got to eat, what, 50 kilos of stuff a day, you spend all your life chewing.
Steve Brusatte: It's a great question because there's nothing in today's world that lives on land that is anywhere near the size of a jet aeroplane, yet so many dinosaurs got up to that size, 35 metres long, 50 or 60 tonnes in weight. And these things were not statues, they weren't buildings that were just sitting there, these were real animals that had to hatch from an egg and had to grow up and had to move around and had to eat.
So why would they get so big? I suppose it was because evolution gave them the opportunity to do it. And it looks like there were a few reasons why they were able to get that big. One of the reasons was because they had those long necks so they could reach high up into the trees and eat food that no other dinosaurs had access to. So they basically had their own buffet up there, so that just allowed them this almost unlimited source of food.
They had lungs that were very similar to birds, very different from mammal ones. They are lungs that have air sacs extending out from them, and those air sacs store air that actually allows birds and these extinct dinosaurs to take in oxygen when they breathe out. It sounds impossible, but when birds breathe in, some of that oxygen-rich air passes across their lungs, but some of it is shunted off to these air sacs, these balloons that are connected to the lung. And then when the bird breathes out, some of that air in the air sacs, which still has oxygen, is then passed across the lung as the bird exhales. The same thing was true of dinosaurs.
But the important thing for the big dinosaurs was those air sacs were able to invade the bones. We see this in birds, but the extent that they invaded the bones of dinosaurs was extreme. And what that meant was these really big dinosaurs could have skeletons that were really lightweight because their skeletons were essentially hollowed out by these air sacs. So they had a strong skeleton but a light skeleton. It wasn't so bulky that they couldn't move around. So that's one of the superpowers that they had that enabled them to get so big and it's one reason I think that modern day mammals living on land can't get that big because we don't have that kind of lung with those kind of air sacs that can hollow out our bones.
Robyn Williams: Yes, we will come to one of the most famous creatures ever lived, T. Rex, in a minute, and whether T. Rex actually had feathers, which is a shocking concept. But I want you to introduce Paul Olsen and what he had to do with President Nixon and you.
Steve Brusatte: Okay. In the book I try to weave in these stories of digging up dinosaurs around the world, but also the stories of a lot of my colleagues, this great diversity of people all over the world, women and men that are discovering all these new dinosaurs, and Paul Olsen is one of them. Paul is a professor at Columbia University, but he started collecting dinosaur fossils when he was a teenager growing up in the state of New Jersey, right across the Hudson River from New York City. And so there were some dinosaur footprints that were discovered in an old abandoned quarry in Paul's home town, tucked up in the mountains, and his mother read about these in the newspaper and then told Paul. I think he was about 14 years old.
And so Paul gathered up one of his friends and they rode their bikes to the quarry and they started to find dinosaur footprints and they were blown away by it and they kept going back. Every day they would work late in the night after school and he became completely obsessed with these dinosaur tracks. They were tracks from the Triassic period and from the early Jurassic period. So they were tracks from around that time that dinosaurs switched from being these humble understudies and became these enormous dominant animals that we all know and love.
So Paul became so obsessed with these tracks and he recognised how important they were. He thought that that quarry should be preserved, this is something that should be turned into a museum or a historic site so the footprints could be safe and so people could come and see them and appreciate them and learn from them. And so like a lot of teenagers do stupid things, brazen things, Paul decided to go right to the top and he wrote a letter to President Nixon. And this was early in Nixon's first administration, it was before he disgraced himself, it was before Watergate, it was before the, 'I am not a crook,' it was before all of that stuff. And so Nixon took a bit of an interest.
Nixon actually almost met Paul, but it was Nixon's aide, Ehrlichman, one of the big villains of Watergate, who turned it down at the last minute. He didn't think it would be good to have the President meeting with this kid who was studying dinosaurs. Bad political optics. But they did exchange letters, and eventually that site was protected. There was some kind of presidential decree that gave it a certain status, and then the company that owned it decided to protect it and you can still go there today, you can see some of those tracks and that's because of Paul Olsen.
Robyn Williams: And you can see a picture of him there in your book and he's wearing a T-shirt with a shocking word on it, 'coprolite', in other words fossilised shit.
Steve Brusatte: Yes, you know what, it sounds a lot better when an Australian says it with your accent, it comes across really nice. If I were to say that it would just sound vulgar I think, and it is a vulgar type of fossil. It's not my favourite fossil. But believe it or not some of the world's best fossil crap comes from here in Scotland, in Edinburgh, just about a mile north of where I live and I'm at home now talking to you. This is a good example of just how many different types of fossils there are. It's not just bones and teeth but we've been talking about footprints, now we're talking about coprolites, there's eggs, there's bite marks, feathers, skin, and it's amazing and we've been learning so much because of all these new fossil discoveries. And a lot of it is totally unexpected. I don't know how many people listening have even heard of fossil crap but it exists and people are studying it.
Robyn Williams: Yes, I've got some on my desk, funnily enough. It hasn't been identified yet but it's truly Australian, a word you have not mentioned yet, 'Australian' dinosaurs, they're there. But I want to ask you, this is the thing, really surprising stuff, T. Rex walks in, you've got an entire chapter, possibly warm blooded, possibly instead of just one on his own, he is fearsome enough, but hunting in packs, and also having feathers. It's a new picture of T. Rex, is it not? I didn't see him in the film Jurassic Park.
Steve Brusatte: That's true, you don't see a feathered T. Rex in Jurassic Park, you're not going to see one if there is a T. Rex in the new Jurassic Park film that's coming out soon, it's just something that the producers haven't put on the dinosaurs. And in fact they didn't know that feathered dinosaurs were even a thing back in 1993 when the first film came out, so you can hardly blame them. But it's true, there's a lot that we now know about T. Rex that paints a new picture of the king of the dinosaurs. And so I have a whole chapter in the book that's a biography of the king.
And so yes, they hunted in packs. We have fossil sites found by some of my colleagues in Canada and in Mongolia where there are numerous Tyrannosaurs that I found together, their bodies are found buried together, and so that's a sign they were living together and probably hunting together.
We know that T. Rex could bite so hard it could crush through the bones of its prey. We know that its body was so big that it couldn't really run that fast. It was probably a slower moving animal, more of an ambush predator. And so that Jurassic Park scene of it chasing down the jeep, that probably wasn't too realistic, although if it did catch the jeep it could have crushed that jeep in its jaws, that's how hard it could bite. And so those are some of the surprising facts that have been learned about T. Rex, mostly over the last decade or so, and mostly because of new technologies being applied to the fossils; CAT scanners that help us see inside the bones, computer modelling that allows us to test how fast they could move and to see how hard they could bite.
But really I think the most surprising thing about T. Rex is that it was probably feathered, and this is just such a different image than the T. Rexs that we are used to, the T. Rexs I remember as a kid. And we don't know for 100% fact that T. Rex itself had feathers, just because it's so hard to preserve feathers. But what we do know is that a few other Tyrannosaurs, some of the closest cousins of T. Rex, definitely had feathers, and that's because their skeletons are found in China in this spectacular dinosaur graveyard in north-eastern China where these entire ecosystems of dinosaurs were buried by volcanoes, almost Pompeii style. So you had these dinosaurs preserved, as fossils, going about their everyday business and they were buried so quickly that the feathers are even preserved and there are two Tyrannosaur species from these ancient volcanoes and are covered in feathers. So that's a really good sign that T. Rex probably had some kind of feathers too. So if T. Rex wasn't frightening enough, just imagine it as this double-decker-bus sized Big Bird from hell. That's the real T. Rex.
Robyn Williams: And not flying, so presumably the feathers were for some sort of temperature control.
Steve Brusatte: That's right, so T. Rex was far too big to fly, it was more like a blimp than an aeroplane, it couldn't actually flap its tiny little arms to get up in the air. And so a lot of dinosaurs were like that too. A lot of dinosaurs had feathers but they were too big to fly or they didn't have big enough arms to support themselves in the air. And so these feathers were probably there to keep those dinosaurs warm. They probably evolved for insulation, similar to why mammals evolved hair. But then later on one group of dinosaurs, like velociraptor, they got smaller and smaller, their feathers started to elaborate, their arms got longer, they developed wings, and then they developed the ability to fly, and that's where modern birds came from.
Robyn Williams: The last dinosaur still living, 65 million years ago there was this impact which you describe so shockingly. I see that 70% of the creatures were wiped out, that is the dinosaurs and plenty of others as well. But in some books it looks as if they lingered for quite a long time, thousands of years anyway. Is that true?
Steve Brusatte: Yeah. We are learning more and more about that extinction. It's like so many things about dinosaurs, there are just so many people around the world looking for new fossils right now and also studying the rocks as well, that we are just learning a lot more about all aspects of dinosaur life and dinosaur history, but especially the extinction. And there's some really exciting new research that has just been published about the extinction.
This new study that's just come out shows that temperature increased by 5 degrees, global temperature, 5 degrees within the first 100,000 years after the asteroid hit. So there was a lot of chaos right after that asteroid hit. This thing was travelling faster than a jetliner, it was 10 km across, it hit the Earth with the force of over a billion Hiroshima bombs, it punched a crater in the crust more than 150 km wide. This was a really, really big asteroid, and it looks like it did most of its damage right away. So probably most dinosaurs died out really quickly. We are talking about hours, days, weeks, months. Some might have staggered on, and birds made it through, we can't forget about birds, but the other dinosaurs at least, some probably staggered around a bit. But what we do know is by 10,000 years after the asteroid hit the dinosaurs were gone, because we have really good fossils that are dated really well from western North America, and there are no dinosaurs at all, not even a single tooth. But instead you have a bunch of teeth and jaws of the creatures that took over from the dinosaurs, the mammals.
And so the dinosaur fall was a sudden fall. They were an empire for 150-some million years, and then really they fell in a day, and I think that's a really, really sobering thought.
Robyn Williams: Sober indeed. Steve Brusatte in Edinburgh. His book, The Rise and Fall of the Dinosaurs is truly marvellous.
- Steve Brusatte
University of Edinburgh
Edinburgh Scotland UK
- The Rise and Fall of the Dinosaurs
- Steve Brusatte
- Macmillan London
- Robyn Williams
- David Fisher