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Paul Barrett: Dinosaurs, Mass Extinctions, Paleontology, Evolution, Past & Future of Life | #54

Full episode transcript below. Beware of typos!

Nick Jikomes

Professor Paul Barrett, thank you for joining me.

Paul Barrett 4:59

Oh How're you doing today?

Nick Jikomes 5:01

I'm well I'm well, how are you? And where are you calling in from?

Paul Barrett 5:05

So I'm calling in from London, where I'm based where it's currently a fairly bright and sunny winter afternoon.

Nick Jikomes 5:12

Excellent. Can you start off by just letting everyone know who are you? What do you do? And what's your scientific background?

Paul Barrett 5:19

So I'm based at the Natural History Museum in London. I'm a paleontologist, and I specialize on the biology and the evolution of the non birds, dinosaurs,

Nick Jikomes 5:31

the non bird dinosaurs. So I already have a million questions. But let's start with something very basic. What are dinosaurs in proper terms? How do you actually define that scientifically.

Paul Barrett 5:45

So dinosaurs are a specific group of reptiles that are distinguished from all other reptiles by set of features that they share that they inherited from their common ancestor who, which was an animal that would have been alive about 240 million years ago. those features are all really rather esoteric features. And they're mainly to do with the fact that dinosaurs very unusually for reptiles walk on their hind legs. And so they modified their back legs and their hips and their back bones and various other bits of their body to cope with that anatomical change. And that's actually how we define a dinosaur. It's to do with a lot of features of their legs and hips.

Nick Jikomes 6:26

Interesting. So I was going to ask later on about by fidelity and things like that, because it certainly to an amateur seems like there's a lot of dinosaurs that walked on two legs, but you're actually saying that this was this was a defining feature.

Paul Barrett 6:40

Absolutely. Right. So it's the other way around the first dinosaur that we would recognize as dinosaur walked on two legs, which is really unusual. It doesn't happen very often in the history of life, the most obvious things that will come to legs, other than humans are birds, which are actually dinosaurs, which is something I guess we'll get back to. And a couple of other things, a few weird things, things like pangolins, and to some extent, kangaroos, and one or two lizards and one or two rodents, but not very many things have done it. So dinosaurs really bizarre in being this big group of animals that learn how to walk on its hind legs only. And the original dinosaur was a biped. All the ones that we see later on that go down onto all fours, are actually going back onto all fours, rather than starting off that way. So another really weird thing about their evolution is they go through this amazing transformation to become two legged animals, and then some of them, give it up and go back to being on four legs.

Nick Jikomes 7:37

Interesting. I think in the beginning here, we can start approximately with some chronological questions. So you've mentioned so far that the earliest dinosaurs were actually walking on their hind legs. I think you said that they emerge roughly a quarter of a billion years ago, 240 million years ago? Can you set that time period up for us? So before the first dinosaur evolved? What was the world dominated by in terms of the animals that were around? And then what did what did that first sort of evolutionary phase look like? How did they start to emerge?

Paul Barrett 8:14

So going back to a period of the Earth's history called the Triassic period, and the Triassic period is the first of three periods in which dinosaurs lived the Triassic, the famous Jurassic, and Cretaceous. And the Triassic begins after a huge mass extinction event 250 million years ago, where about 97% of the animals that lived on land died out. This was a major event, which created a huge amount of empty ecological space on the planet, which then new groups of animals evolved to fill it. So we have a world at the beginning of the Triassic period that's not particularly diverse, that doesn't have lots of lots of different animals around, but does have lots of opportunities for newly evolving animals to find different ways of life. And if you're talking about the geography of that time, the earth also looks quite different. All of the world's continents at that point are joined together into a single landmass called Pangea, which would have essentially had a single coastline going all the way around no big seas or anything like that separating the continents. And as a result of that the climate at the time was also very different. It was much warmer, it was much less seasonal, with a few differences between winter and summer, and the interior of that continent was largely composed of searing deserts, while the outsides were a bit nicer to live in, but still had to put up with very monsoonal type climates ranging between extremely wet and extremely dry depending on the time of year.

Nick Jikomes 9:50

What so before the dinosaurs emerge, what kind of what kind of animals were around like it was it was there any major patterns there?

Paul Barrett 9:59

Was so before dinosaurs were around, the predominant type of animal that you would have seen everywhere was something called a synapses. And these are animals that used to be called mammal like reptiles, but aren't actually reptiles. These are animals that are our own very distant evolutionary ancestors. And these would have been occupying most of the different roles of top predator top plantea to, and were very abundant at the time as well. So if you'd like these were the cause of the top ecological dogs of their day, they were the kind of bread and butter animals you would have seen walking around. And the vegetation we saw at the time, but also been quite different. We're used to living in a world filled with grasses and flowering plants and shrubs. in those in those times, there are no flowering plants, so no flowers. Instead, the vegetation is dominated by things like firms, tree firms, primitive trees, like Kinkos, conifers, so would have even looked in terms of the various tations with very different place. So a lot hotter, a lot more impossible, as certainly in some areas, and also just a general landscape sort of look very unfamiliar to most of us.

Nick Jikomes 11:14

So at the time, at the time, that the first dinosaurs were evolving 240 million years ago, and even before that, there was these things called synapsids. And they were the basically the precursors to mammals. And I guess my secondary question there is, was the mammalian lineage already evolving at the time of the earliest dinosaurs?

Paul Barrett 11:36

That's absolutely right. So the synapses are our early ancestors, they were already developing features at that time that we would recognize in mammals. So we're starting to experiment with things like fur, and mammary glands. And the very earliest true mammals that paleontologist recognizes mammals occur about the same time as the first dinosaurs. So dinosaurs and mammals have lived alongside each other for almost all of their evolutionary histories.

Nick Jikomes 12:03

I see. So if you go all the way back to the beginning of the dinosaurs, mammals were pretty much already there. We were always side by side dinosaurs won in the sense that for a long time, they became the dominant animal type. And I guess we'll talk about that. And then eventually, we'll get to the extinction. And the mammals sort of take over after that. Is that roughly what happened?

Paul Barrett 12:24

That's exactly right. So to start with mammal ancestors were the most common at abundant animals, then for reasons we don't really fully understand. They kind of have their heyday. They have an extinction at the end of the Triassic period, and they reduce the numbers, although true mammals still hang on there. They remain there all the way through the time that dinosaurs take over. And then when dinosaurs removed from the picture, a few million years later, mammals become again, the most important land living animals.

Nick Jikomes 12:53

So there's a few things I want to do. I definitely want to ask about some of the patterns that we see in the fossil record going from Triassic Jurassic Cretaceous. I want to ask them specific morphology and other questions. But maybe before that, it would be good to talk about fossilization as a process itself, can you give us give us a quick like fossilization 101, in terms of how that happens, and then how maybe how that introduces bias into what kind of dinosaurs and other animals we actually see in the fossil record

Paul Barrett 13:25

should be happy to So becoming fossilized itself an unusually rare event, what happens has to happen is the animal has to die in a place where it's going to be buried relatively quickly, which means it's living in environment where there's lots of mud or sand around to bury it fast enough before the body just disintegrates due to scavengers coming along and pulling it apart or the ravages of weather, helping it to disintegrate as the animal rots down. So these are often places like animals that die near on floodplains, or that gets swept into a river or buried by a sand dune, or flew at sea and get buried on the sea floor. So the key thing is quick burial. And one of the reasons why many fossils are incomplete is because of that process is because at some point in that process, another scavenger comes on takes a bit apart, rots away, the current removes part of it before it gets in tuned and sealed in the rock. So once it's buried, it basically then gets compacted in those soft sediments that then gradually over time turn into rock. The bones or the shells themselves often become replaced by slightly different minerals that come in through the water that are flowing through those rocks as they form. And eventually after a lot of alteration with a lot of heat and a lot of pressure, a fossil is formed. And for obvious reasons. We generally get fossils of the hard parts of an animal, the bones or shells, whereas the soft parts generally just rot away. So it's very rare that we get evidence of the soft parts we do sometimes. But mostly, we're left with the hard parts of the animal. And those are the bits of evidence that we have then to try and work out how they lived and how they interact with each other.

Nick Jikomes 15:14

Is there anything? Like the classic amateur image of a dinosaurs of a quite a large organism? This the size and the physical size of the bones have anything to do with their preservation qualities? Do we see a bias for like big animals? Or is that not true?

Paul Barrett 15:32

Actually, rather oddly, we get more fossils of little animals. And that's for a couple of different reasons. One reason is simply that at any one time, there are more little animals alive. Just future basic rules of ecology, there are always lots of small things and relatively few large things. The other thing that counts against getting big animals is that there's a lot of that animal to bury. And there are lots of bits of that animal that scavengers and predators can take away. So finding really complete large animals is relatively rare, saying that some large bits of large animal say, for example, a thigh bone, because they're large lumps of bone, and they're quite strong, they can hang around in the environment quite a long time without being broken down. So finding occasional large bones is fairly common, finding lots of large bones from a single skeleton together is quite rare. So we know a lot more about the history, if you like the history of life of small animals, because there are a lot more of them and a lot more of their fossils to find, than we do about the larger ones, which is why we're constantly updating our picture of what dinosaurs and other extinct animals look like, as we do find those new specimens coming out, that takes a lot of effort to get that new new data to come to light.

Nick Jikomes 16:53

Now, on the topic of fossils, and physically finding these things, you know, the classic image of a paleontologist is someone, you know, taking an educated guess about where to look, and going out and you know, just physically cutting into the rock and digging these things out. Obviously, you have to dig them out once once you find them. But I'm wondering if you know, in the last 510 20 years, what has the use of technology looked like in order to get better at finding where the fossils are, and getting them out? You know, one image I have in my mind is that that scene at the beginning of Jurassic Park, where they're using sonar, or something, do you guys have any interesting uses of technology that have emerged in the last say, decade?

Paul Barrett 17:37

Unfortunately, not we've mainly stick with that traditional method of walking around and looking at the ground. And that remains the primary way that we find dinosaurs. So although people have experimented with things like ground penetrating radar, it's not actually very helpful. The reason being just the basic physics of it, those kinds of techniques are looking for differences in density below the ground. And actually, the dinosaur bones are the same density largely or more or less as the rocks at their founding. So those kinds of techniques just generally don't pick up those kinds of subtle differences, unfortunately, so it's not been used very much. Another method that has been tried once or twice is using radioactivity to see if we can find dinosaur bones. Because for reasons we don't fully understand chemically, fossil bone, for some reason soaks up radioactive elements from groundwater preferentially. So they're often a little bit and sometimes quite radioactive. And so people have tried using sensitive Geiger counter based instruments, basically, to hunt for dinosaurs. But to my knowledge, so far, that's only been done successfully, once ever. So again, that partly comes down to Equipment that partly comes down to the fact that, again, you're dealing with quite a lot of background information, which is often difficult to assess when you're actually just looking for potentially a small objects in a very large area of rock, other areas where there is going to be more interest. So I think come with drones. So our initial search images you like comes down to knowing areas that are good to look for dinosaur fossils, and indeed any kind of fossils. So with dinosaurs, we know they lived on the land, and we know they lived at certain times. So we're looking for areas with rocks of the right type and have the right age. And where an areas where preferably there's not too much vegetation cover because we're looking for things that are weathering out the surface. We don't just go out and dig pits and dig holes because there's very little chance you'd find things at random that way we need some kind of indication there might be something lurking around nearby. So we go out we use information that geologists provide us because geologists go everywhere in their search for raw materials and to work out how continents are formed and mountains are built on then we use that as a guide to go to those areas. Sometimes those geologists even notice that there might be a good spot to go and look for those places. But finding those areas is being made a lot quicker by using things like drones, because often you have a lot of ground to cover. And although I don't think anyone's yet found an actual fossil using drones, for example, we do know that colleagues of ours who work on human evolution have used Google Maps to find promising cave sites. And they've been using those with some success to narrow down their searches of places that might be good. So I think technologies like that, that will help us narrow down those areas to finding the most promising looking areas are eroding or kind of accessible rock in very large landscapes often that are otherwise difficult. So check on first, I think that's something that is going to become more and more useful as and using things like satellite imaging data to

Nick Jikomes 21:00

interesting so you know, that stuff will help at the early phases of identifying a promising site. But it sounds like what you more or less said was just based on the physical properties of the fossils themselves, and the similarity to the rock they're embedded in, you pretty much got to stick with the old fashioned methods, there's no, there's no fancy trick here.

Paul Barrett 21:21

Unfortunately, not, it is literally walking with your face to the ground, hoping that you spot something that looks different from the surrounding rock. And sometimes it's self, that's hard, you walk around for a day, and you pick up lots of lumps of rock that you think might look like the edge of a bone might look like something slightly different. And it turns out to be a pebble, or a strange soil concretion, or, in some cases, a dried, animal dropping all of these things, you know, can have been mistaken by me and colleagues and things that look really interesting. You pick them up, you get an idea of what actually looks like in the texture of it, and then you're able to assess it. A lot of the times you're wrong. Other times you get it right. So there's a lot of trial and error, and a lot of basic, just getting hot and sweaty and walking around and keeping our eyes peeled.

Nick Jikomes 22:09

What are some of the classic or some of the hotspots today where people are pulling a lot of dinosaur bones out of the ground? I vaguely remember as a child learning that, you know, there's certain places in the continental United States that you know, you find a lot of certain types of dinosaurs, I'm assuming there's at least probably a few places that are hotspots, is that true?

Paul Barrett 22:32

Absolutely. And that comes down to where the right rocks of the right age are that are collectible at the surface of the earth. And where again, there's not necessarily that much vegetation in the end in the way. And hopefully also not too many things like cities or farms built on top of these places, so you can actually access the rocks themselves. So western North America has been a particular hotspot for dinosaur discoveries in a belt that goes up from essentially along what are now the Rocky Mountains from all the way from New Mexico in the south up into Alberta, and Canada. And that area has large amounts of dinosaur age rock exposed at the surface in Badland type scenery where it's constantly being eroded. And so removing rock, allowing new discoveries to be made all the time. And historically, that entire area has probably feel most of what we know about dinosaurs, or at least certainly most of what we knew about dinosaurs, through most of the early part of the 20th century, they were the richest hunting grounds. But they're not the only ones. Historically, Europe produced quite a lot of material when people are mine and quarry more by hand. So the earliest discoveries of dinosaurs that were named all come from Europe, which is not really surprising in that there was a lot of industrial activity. So there were lots of quarries, there are lots of rocks at the right age in Europe. And similarly, it's also just because of the accident of history, the air of the world where these studies began. And so there were people looking for this kind of material. Europe still produces new dinosaurs, but a much lower rate. Now, obviously, small land area, there are lots of people in Europe as a result, lots of land is taken up by farming and agriculture and urbanization. And as a result, our chances in Europe for finding new materials are still there, but they're a bit lower. But the other key players now are, I would say eastern Asia, China and Mongolia have fast fossil fields that have been fueling a revolution in dinosaur studies over the last 20 or 30 years, a bit longer in the case of Mongolia, and also southern South America and Brazil and in particular in Argentina, which also have the advantage of huge open landscapes with rocks the right age, so many of the most exciting discoveries recently have been coming from those areas of the world.

Nick Jikomes 24:53

I'm wondering if what we can do now is I'll ask sort of a big a big question. Question about evolution. And you can probably just start to take us through some things. And then we'll probably start diving into some interesting topics that that you mentioned. But you know, we start out by saying the dinosaurs, properly defined evolved 240 million years ago, that was Triassic area. And then you go from Triassic to Jurassic target Cretaceous and extinction. So I'm wondering if you could just paint with a broad brush? What are some of the big evolutionary trends that you see in the fossil record going from each of those areas to the eras to the next one. And probably along the way, we'll just stop in and riff on some of those. But you know, from the earliest dinosaurs to the Jurassic, what was changing?

Paul Barrett 25:43

Sure. So when we get our first dinosaurs appearing on Earth, our first definite dinosaurs are about 235 million years old. And they all look very similar to each other. They're all bipedal, they're all small dinosaurs at the start is not particularly large animals, only about a metre and a half in length. And the other thing about them is they're rare. They don't start immediately as a common group, they start off as animals that are definitely minor players in their ecosystems. And those ecosystem is dominated by these synapses, type animals, and also by a large number of other reptiles that are more closely related to crocodiles than they are to dinosaurs. So dinosaurs were very much a small players in this world. And these very early dinosaur fossils are mainly restricted, just in South America. So it seems that southern South America might almost acted like a little bit of a cradle for dinosaur evolution. And we're not sure if they definitely appeared there. But it certainly looks like they were doing very interesting things there at that time. And there's relatively relatively little didn't from the rest of the world of dinosaurs being around at that time anywhere else. So it seems that the southern hemisphere is key in the origin of dinosaurs. And so these animals are around, and then they persist like that for a few million years. And then, a pool of large extinction events take place at the end of the Triassic Period, not just one big extinction, but a kind of several pulses of extinction take place. And that seems to have been the key that then allowed dinosaurs to take over. Those extinctions didn't really affect the dinosaurs very much. We don't know why, although there are various bits of speculation why they didn't seem to affect the dinosaurs. But they did strongly impact the synapses and the other reptiles that were living at that time. And many of those groups became extinct, or reduced a lot in their abundance and their importance. And these extinctions seem to be linked to a major event in Earth history, which was the opening of the North Atlantic Ocean. So we've already mentioned that at the beginning of the Triassic, all of the continents are linked. During the Triassic, a huge amount of tectonic activity starts, which starts to push North America, and Africa and Europe apart from each other, opening up a kind of, if you like proto, North Atlantic Ocean, and that opening up is associated with vast outpourings of lava. We're not talking about giant volcanoes spewing forth explosive eruptions, but a constant process of lava welling up from the fissure between those continental areas, and gradually welling up to push them apart. And this huge amount of volcanism has a technical name. It's called the central Atlantic magmatic province. And it's associated with this long term, ocean forming event. And obviously, with that much new material welling up from inside the Earth, we get huge amounts of gas and all sorts of changes to the climate that accompany that the climate becomes wetter than than it was previously, it starts to become a bit more seasonal, because the opening Atlantic Ocean brings starts to bring ocean water closer to the shorelines rather than all being one large homogenous sample land. And as a result, we get a lot of climatic change around this time, too. And it's been speculated that these climate changes may have in some ways impacted badly on those other dominant roles, but allowed the dinosaurs then to take over. So that's one of the big changes we see. And concurrent with that, as we see these other reptile and synaptic groups disappear. We start to see dinosaurs experimenting, ever evolutionary in various ways. So we start to see them increasing in size, we start to see them increasing in absolute numbers and living in herds and experimenting with sociality. We start to see them broadening their distribution all over the earth. So dinosaurs very quickly gain a global distribution. So this does seem to have been a really key event in their history that sets them up from being ecological oddities, which is what they were to start with through to becoming the most important land living vertebrates of their time for the next 100 and 50 billion years.

Nick Jikomes 30:13

I see So Triassic to Jurassic, you start to get the continents pulling apart. This leads to various changes, geologic changes, climate changes. And even though we don't know and may never know the exact details, this is the time when the true dinosaurs start becoming more common becoming more diverse. One thing that's really one thing that's obvious is okay, when dinosaurs become more common, you're gonna start to see more bones in the fossil record, when they start to become bigger. That's also easy to see because the bones are bigger. But you also said they're experimenting with things like sociality and group behavior. How do you actually discern something behavioral like that from the fossil record?

Paul Barrett 30:57

There are a couple of ways we can do that. So one way is just by looking at the bones themselves, sometimes we're lucky enough to find a group of dinosaurs preserved together that were clearly preserved in a single geological events, a flood, or a Ashfall. Those kinds of events can literally record an instant in time where the animals that were living together died at the same time, and were in tuned at the same time. And we call that phenomenon a bone bed, where we have many individuals often at the same species cap to get one go. And when we get those groups, we can be fairly sure that those animals have come together or were living together at the time of their death. The other line of evidence we have for that actually comes from fossil footprints. Because again, fossil footprints generally record a very small time. Most of them are found along riverbank word riverbanks or long coastlines. And in particular, those ones that are found along coastlines are forming in between the tides. So there's a limited time of a few hours, where animals are moving backwards and for a long coastline before their footprints are being buried by the sand that's being then laid down over them again, by the incoming tide. So we can see when we will see lots of, for example, lots of parallel dinosaur tracks that aren't necessarily cross cutting each other or overprinting each other, but they're walking in parallel for long distances, that seems to suggest that you have a group of these things moving side by side. And we know that that was happening within the space of a few hours, at one particular time, that many millions of years ago. So those are two direct lines of evidence for groups of dinosaurs being in the same place at the same time, which then allow us to infer they might have been social.

Nick Jikomes 32:43

So going from Triassic to Jurassic, you've now got more dinosaurs, you've got bigger dinosaurs, you've got more diversity among them. At the beginning of the Jurassic, do we have yet any or very many of the dinosaurs that are the classic examples that people will be most familiar with and popular culture? And whether or not that's true? What is that? What is the change you start to see in the Jurassic period look like?

Paul Barrett 33:10

So I think most of the dinosaurs are alive in the Triassic and into the early part of the Jurassic period are fairly unfamiliar dinosaurs to people. They're not the ones that we normally think of, in terms of either kind of popular depictions of dinosaurs, or even that often actually in museum collections, except in a few of those parts of the world where those dinosaurs are particularly well known from. So for example, many of the major museums in Europe and North America that I've visited, have relatively few of those types of dinosaurs on display, most of the displays concentrate on the larger, more spectacular things from later on in time. So unfortunately, some of those animals are really interesting in their own rights. And also important because they show how the different major families of dinosaurs start to differ from each other and traveled down their own evolutionary pathways, they probably have a bit more, a bit less impact on the kind of public imagination of what a dinosaur looks like. But that does change through the Jurassic period. So as we go through the Jurassic, we see a number of more changes in the kind of physical environment of the Earth. The those continents continue to separate from each other and eventually split into a Great Northern landmass called Eurasia and a great southern landmass called Gondwana, which is separated by a shallow ocean, separating them. So the trajectories of evolution of the animals living in North and South differ a little bit from that time onwards, because they can't mix as much as they did when we had just a single landmass that they could move around more easily. And also, the climate starts to become actually nicer. It still remains very warm, but it becomes wetter. And that's because of the influence of these new oceans now allowing more moist air to get towards the centers of these continents than was previously possible. So the landscapes become wetter They become lusher. And as a result, the world becomes a little bit easier for animals Sullivan in particular large animals, because suddenly there's now a lot more plot life and a lot more variety of vegetation around. The trends we see in dinosaurs at this time are continuing trends in some groups to large signs, culminating in some of the first really gigantic dinosaurs ever to live on the earth things that are getting like Diplodocus, which is getting up to like 30 meters long. I almost like Brachiosaurus which are weighing up to 50 tons. So these are really big. And now also, we're starting find those dinosaurs that more familiar to people as well. So these, this is the age the First Age, if you like the true dinosaur giants. And alongside that, we also see a number of other trends, they start to experiment with different ways of feeding different diets, they are still experimenting with body size, because not only are some dinosaurs getting larger, some are also starting the opposite trend are getting smaller, which becomes important for other reasons, later on. So there's still quite a lot of experimentation at this time. But during the Jurassic, we see most of the big subdivisions of the dinosaurs take place early in the Jurassic periods, establishing those different major groups. And then subsequent to that each of those major groups take their own pathway and develop their own specializations in different ways. So it's a great time of experimentation followed by consolidation of those different ways of life.

Nick Jikomes 36:31

In the Jurassic era, how long ago was that?

Paul Barrett 36:35

So the Jurassic period starts about 200 million years ago, and extends through to 145 million years ago.

Nick Jikomes 36:42

I see. So you're talking 10s of millions of years just for this era. And this is the period where many of many of the most famous dinosaur examples were actually around.

Paul Barrett 36:52

Exactly right. And in particular, the later part of the Jurassic, so about 140 million years ago now. So 150 million years ago, is when we have some of those really classic dinosaurs that are particularly well known for North America. So things like Diplodocus, things like Stegosaurus, big carnivores, like Allosaurus sees animals all lived alongside each other, in what's now western North America between about 155 150 million years ago.

Nick Jikomes 37:23

And I know there's probably not one answer to this question, but roughly, roughly speaking, from this era, say, how many species do we know about today, approximately? And what do we think that's 1%? Of what there was 50%? Of what there was? Do we have any sense of that at all?

Paul Barrett 37:42

That's a really good question. I can't pull the answer to that off the top of my head. Actually, Triassic dinosaurs are relatively rare, so they're relatively few of them in comparison with the later periods. The witches time for dinosaurs is the Cretaceous. That's the time when we know most dinosaurs from the kind of Jurassic is also fairly well known, certainly much better known than Triassic but I don't know, numbers off the top of my head. But it's certainly the case that we know a lot more, or we have a lot more different types of dinosaurs then. But this comes back to one of your earlier questions to do with bias. One of the reasons for that pattern might simply be that younger rocks are easier for us to see, they're often the ones on top of the older rocks, so they're often more of them at the surface. There are have been fewer opportunities for those rocks to have been eroded away or destroyed through time. Whereas if we go back in time, those rocks can be buried deeper, or they could have been eroded away, because we're talking about really long periods of time. So our knowledge of the past gets patchy, and the further back we go. So the fact that we know more about Cretaceous dinosaurs than the Triassic dinosaurs might represent a genuine evolutionary signal. It might mean there are lots of lots more dinosaurs in the Cretaceous. Or it might simply be we've had a lot more opportunity to find those dinosaurs in the first place. And that's actually an active question within the subject on finding out the balance between those two factors to work out what the trajectory of the richness of dinosaurs was, through time. Was it a line that went up slowly? Was it a line that went up very quick, clear, did to plateau, and then stop? Did it peak and trough for different reasons. And we're trying to find ways to disentangle the biases that we have from the geological record, with the biases there might be from the action of discovery because obviously, we're led by where paleontologist go to find fossils, and also the real biological processes that might have created little wiggles in how many dinosaurs there were at any one particular time. And this is something that we're putting a lot of effort into trying to understand at the moment and we don't yet have a really good answer.

Nick Jikomes 39:53

So one of the things that you said earlier was that your personal specialty was in non avian Dinosaurs. So I interpret that to mean, this is this is the branch that did not give rise to what we recognize as birds today. When did that split start to happen? And what are some of the essential differences between those two branches?

Paul Barrett 40:14

So birds, actually, the way we think about classification is almost like a nested set of Russian dolls. So we think about groups within groups within groups within groups. So dinosaurs have a single common ancestor, that single common ancestor led to all the different types of dinosaurs we're aware of, including birds. So it's not the birds are descended from dinosaurs, birds are dinosaurs, they're part of that group, they have the same ancestor, as all of the other dinosaurs. So we tend to think of them. Historically, we've tended to think of them as quite separate. But over the last 2030 years, we've been trying to bring them more thoroughly back in, because understanding bird biology is an integral part of understanding the biology of dinosaurs as a whole, because they're just part of what dinosaurs did. So but the first birds are, there'll be see as distinct, or the number of dinosaurs we think, occurred in the Jurassic period, again, while we stood in the Jurassic, again, about 145 million years ago, and there's a little bit of argument over, which is the earliest troopers. And this comes down to a lot of rather Tarek arguments over definition, what actually defines a bird. In the old days, it was easy. When I was a student, it was really easy. Birds had feathers, it's as simple as that. Birds had Severs. And they flew, it was a clear difference. And there are few other features like that, these days, because lots of dinosaurs are now known to have feathers that were not birds. And a lot of the features that we used to think of as unique to birds seem to have their origins deep in the dinosaur tree, it's become increasingly difficult to come up with a clean definition of where we draw a line between a burden a dinosaur, which is one of the other reasons, we now tend to bring them into the dinosaur fold, because there is very much a blurred transition between those two. Almost every feature we see in a bird, we can trace its origin back well before the origin of birds to some other dinosaur group now. So for me, a good colloquial, if you like, an easy rule of thumb is birds flew dinosaurs didn't, it seems that birds finally got all of the bits of kit necessary to be able to be active fliers, whereas dinosaurs didn't, they might have had feathers. And they might have had many of these other features. But they didn't have that final bit in the toolbox that enabled them to be active fliers. So for me, that's where the kind of definition comes. And the earliest bird that I think, many paleontologists would recognize, is an animal called Archaeopteryx, which is from about 145 million years ago, it lived in what's now Germany. And it's known from several fossil specimens now, which are all coated in feathers. And that is definitely if not the earliest birds, it's very close to being the earliest birds.

Nick Jikomes 43:05

And what does fossil evidence for feathers actually look like? Is it is it mostly like an imprinting of the feathers in the surrounding rock? Or do you actually get any, any more concrete indication of the feather material itself?

Paul Barrett 43:19

Well, in the case of Archaeopteryx, which is the earliest known example of a feather from the fossil record, their imprints their impressions around the skeleton, that are in prison, served in a beautiful, very fine grained limestone that captures very high levels of anatomical detail. But in other fossils from slightly later in time, we also see organic impressions of these feathers. So we actually see. And these impressions that are captured by the action of bacteria that are very quickly preserving those features as the animal is fossilized. And so in those, we see a lot more detail in Archaeopteryx, we're looking at the impressions of those structures in very fine rock. Later on, we're actually seeing the chemical ghosts of those things, which actually give us quite a lot more detail, even to the extent that some of those features also preserve the intracellular structures that were present in those feathers originally.

Nick Jikomes 44:13

And then, so it sounds like there's a lot through a lot of creatures that had feathers, feathers were, if I'm understanding around before flight was they were just one piece of the flight puzzle that that we associate with modern day birds. And we learned over time that more and more dinosaurs actually had feathers. I want to talk about this a little bit more. What do we think that means? So what were feathers doing for these creatures before they were a component of flying? And I do want to ask about velociraptors I know this is an example where I think we discovered eventually that they were covered in feathers. So what were these feathers doing for the the earliest dinosaurs that have them and then maybe maybe we'll get into a discussion about the Raptors.

Paul Barrett 45:00

There's a bit of debate at the moment about where feathers appear in dinosaurs. So some of my colleagues think that maybe this is a feature that characterizes all dinosaurs. And eventually we'll find evidence that they appeared in every single dinosaur group. I belong to a different camp, where we think that actually the story of feathers is largely a story to do with the animals that are fairly close to bird origins, the meat eating dinosaurs, and it does look like a lot of the meat eating dinosaurs would have had feathers. There's quite good evidence from different groups of dinosaurs as direct evidence of feathers that they had them. So it looks like they were an important part of nice Eating Dinosaur evolutionary history. But we're still waiting to see more evidence that they might have been more generally important to dinosaurs. But they certainly appear in animals that are very distantly related to birds, but kind of great, great, great uncles of birds, as opposed to being very close evolutionary cousins. And they initially appear as hairlike structures as sort of filaments. They're not here, they're chemically different from hair. So our hair is made of one form of a protein called keratin. Feathers are made of a different form of that same protein, they have different evolutionary origins. So these filament light structures in birds are made of the bird type version of that protein. And then through time, we actually ever see a whole sequence of fossils that show how you turn that single filament in something that then has little barbs on it, how they become more complex by adding further and further barbs and turning themselves into kind of aerodynamic surfaces or display objects. So we have very convincing sequences from both the fossils that actually match also developmental bowl objects when it's on how feathers are built, to show how those structures came about. And initially, as I mentioned earlier, it was thought that actually feathers and Flight were the same thing, they must have appeared for the same reason. But it turns out that feathers are in animals that are clearly not flying animals whose proportions and size and his musculature is simply not capable of flights. And there are two or three competing ideas for why feathers might have evolved. And actually, all of those ideas, they're not mutually exclusive. And it could have been that feathers actually were used for several things at once, when they first appeared. So one of those suggestions is that it was for installation. A lot of dinosaurs were very active animals, it's been suggested they had higher metabolic rates and other reptile groups. And these things might have appeared in the mall animals in order to help them retain that heat, so they could be more active. Related to that, it's also been suggested that maybe they were useful for helping to brood the eggs, because dinosaurs all laid eggs, and the small dinosaurs at least probably sat on their eggs. And it may have been a feature that allowed some of those dinosaurs to assist with keeping the eggs at certain temperature. And the final idea, which is actually my favorite idea is that they were for display. And that these things originally evolved basically as a way of showing off. And one of the reasons for thinking that might have some idea to it is that a lot of the earliest featherlike structures appear on things like the arms. And they also appear on the tip of the tail and fan like arrangements. These look like classic places that you would want something for display by sort of showing your arms literally like a peacock. Exactly. So like things that you could show off that a potential mate or a potential rival for some form of display. And we also know that some of these very early dinosaurs were the feathers were not particularly spectacular. They were these kinds of coatings of fuzz. But we know from some spectacularly preserved fossils in China, that even in those relatively fuzzy unshowy looking coatings of feathers, that they were colored, and that they had color banding.

Nick Jikomes 48:50

And I actually had this in my questions here. How on earth do you discern something like color?

Paul Barrett 48:59

I 10 years ago, when I used to give talks on dinosaurs, I just used to stand in front of audiences and say, We will never know what color a dinosaur was. You never get preservation of the original pigments in in a dinosaur. It's something that paleo artists allowed to exercise their imagination over because we'll never know. If probably something like birds, probably something like lizards, we kind of use our own imagination to fill in the gaps. And then about 10 or 15 years ago, technical advancements in geochemistry and in microscopy, started to reveal clues to Dinosaur color. And some of these spectacular preserved in particular Chinese dinosaur fossils, ones that were already famous for having feathers. It turned out their preservation was good enough that when you looked at them chemically, you could find antibodies to the different proteins and and to prove that these things were made of the same protein that bird feathers were on. Then going further. They were able to to use my crossbow keep my crossbow kids are working, never say microscopy methods to look at structures within the feathers that give an idea of their coloration. These are things called melanosomes, which are organelles within cells that include pigments, and they have a living animals. melanosomes have characteristic shapes depending on the pigment and tighten them. So by looking at the shape of these little objects within the feathers, you could actually come up with a suggestion that maybe this feather maybe was black, or this feather maybe was dark brown,

Nick Jikomes 50:35

I see. So if I'm following this, the basic picture I have, in my mind is certain places with certain geological properties, certain physical properties of the sediment, perhaps the sediment is extremely, extremely fine. And so it gives you a lot more structural detail, you can not only see the macroscopic qualities of the organism that's preserved, but you can literally point a microscope at it and see cellular level features. And what you're saying is it just happens to be that some of these pigment containing cellular organelles have different shapes depending on the color. And so if you can see the shape of this thing, you can infer what pigment color must have been there.

Paul Barrett 51:15

That's an excellent summary. And that's exactly what some of my colleagues have done with these dinosaur fossils. About five or six dinosaurs have now been subjected to this type of analysis. And they've all come up, they've all been found to have a range of colors ranging between blacks and grays and dark browns, because those are the types of colors that this pigment melanin contained within those melanosomes generally give. There's also a few examples of things like russets and reds, again, also, colors are given by melanins. There's also the possibility one day, and I think this is a, again, an emerging and fairly fast moving field, that will also be able to look at structural colors. That is the colors that happen not because of a pigment, but because of the physical structure of an object. So if you think about a lot of the iridescence that was like a hummingbird or three things, exactly, that's caused not necessarily by pigment, but actually by the interplay of the structure of the feather with light and how the light is refracted and diffracted through those structures. And we should be able to see some of those details if they're present in some of these really exceptional fossils, too. And colleagues of mine working on other types of fossils, have found evidence for that, and things like fossil beetles and fossil insects. But we're still waiting for an example of iridescence from a dinosaur, but I'm sure it won't actually be to live, I think we'll get that within the next few years.

Nick Jikomes 52:41

Interesting. You did say something about antibodies that had to do with this, are you saying like the the antibody itself is somehow preserved? Or you can you can see an echo of it in the shape of something.

Paul Barrett 52:55

I know it's not smart, it's using antibody primers. So we use an antibody for the protein that we would say is present in say living birds. And those bind chemically, to the to these fossils.

Nick Jikomes 53:11

So the antibodies against the proteins that work biologically today that stick to something today living organism still stick to the fossil of that ancient protein today, in some cases.

Paul Barrett 53:25

Absolutely. So some of my colleagues have suggested that you still got traces of that original chemistry there. I mean, there have been claims of lots of preservation of different proteins. And there's fairly good evidence of the preservation of things like collagen in dinosaur fossils, and there have been claims of other types of protein to including hemoglobin, although those claims have been more contested. And obviously that brings us on to the subject of DNA. And there have been claims of dinosaur DNA, but they remain very, very contentious. The early claims were generally disproved quite quickly, they turned out to be human contamination. They were largely when the samples were relooked, at most of the DNA, in those cases turned out to be human gut bacteria, which are everywhere. And so they were just cases of contamination. There have been more recent claims from labs using strict protocols that they're finding a kind of nucleotide like material. But again, these results have not yet really been replicated. And so it's still an open question. Although many of my colleagues who work on ancient DNA, think that it's probably unlikely given how quickly DNA breaks down in the environment.

Nick Jikomes 54:39

Yeah, my gut instinct there would be you know, if you find some remnant of nucleotides, maybe you will, but it's not going to be preserved in the sequence. You know, in the intact form, it would have been for the organism although, I mean, I'm really just speculating. I you know, I vaguely remember. So this is related to the general topic of You know, just finding any sort of soft as opposed to hard material that might be preserved over these long periods. And also just general questions I have about physiology. Obviously, the morphology side is perfectly intuitive because, you know, you can just see what the bones look like and everything. But more generally, how does one make inferences about dinosaur physiology.

Paul Barrett 55:22

So this comes down to a number of different proxies. So one of the most commonly used ones comes down to looking at Dinosaur growth rates. And then generally making the assumption that if an animal grows quickly, it was probably able to fuel its body and was living actively and possibly with a high metabolic rates. So this is probably the the method that's most often. And we can get an idea of growth rates in a relatively simple way. And that is by cutting open a dinosaur bone. And bone forms cyclically in response to environmental changes. So during a good season, the bone grows quickly during poison, it grows slowly. And those alternating patterns of growth, which are normally annual lay down rings, rings of fast growth versus narrow rings of slow growth, and so on, and the cyclical pattern. So when we can't open that dinosaur bone, it's simply a case of counting the rings to work out how old the animal was, at the time it died. And then we can use various other things like the circumference of the animal's leg bones to get an idea of how much it weighed, because that's a physical feature related to its body mass, which we say living up to. And by combining those two things, we can then get a rate of growth. And it turns out that dinosaurs grew much faster than any other reptile that we know about much, much faster. Some of them growing at rates are definitely comparable with loads of living mammals, and none of them grow as fast as spreads grow fast, and almost they think, but then again, birds are living dinosaurs, so perhaps not comparing like we like. But certainly they grew very fast, much faster in a crocodile or a turtle or a lizard, or anything like that. And so if you find even isolated bit of the top bone that shows those pro things, even if you only have a chip of that bone that you don't know if it's from a dinosaur or not, if it's of that age, and it was growing that quickly, you've probably got a bit of dinosaur in your hand.

Nick Jikomes 57:20

So you can you can infer how fast they're growing by looking at the bones. It's not unlike a tree ring or something. And this tells you something about their metabolism. And for me naturally, this brings up the question of something like warm blooded versus cold bloodedness. And you know, I remember vaguely hearing at some point that maybe some or even many dinosaurs were warm blooded. And I'm wondering if, if the answer to that question is, is right at about this spot.

Paul Barrett 57:48

I think, going back historically, dinosaurs were just viewed as scaled up deserts. So it was assumed for most of the history of dinosaurs studies, through at least the 1970s that these were largely a kind of large, sluggish, basically scaled up iguanas. But a large number of studies since then, I tend to overturn that rule, and most people would now regard dinosaurs as having elevated metabolic rate in comparison with reptiles, although there is still a debate over how elevated that rate would be and how they achieved those higher body temperatures and higher metabolisms. So for example, the really gigantic dinosaurs probably didn't have mammals style, Will bloodedness Because they would probably ended up overheating. If they did these a huge animals that would be making a huge amount of internal heat, that they would have to dump somehow, in order to avoid the heat. And also it would require vast amounts of fuel to keep those kinds of bodies going. But equally, if you're very large, you can keep heat internally, very, relatively easy. So as you digest food, you produce heat, as you move around, your muscles produce heat as always product. And all of those things added together produce, something's been called by some people, inertial homeo Cerney. And that is basically maintaining a constant high body temperature simply by the fact that you lose your internally generated heat quite slowly. Even if your metabolic furnace is set. The thermostats not particularly high, because you're making all this other heat simply by moving around and digesting things. And that he is difficult to get rid of, maybe you end up with a higher constant temperature. But for smaller dinosaurs, there's a slightly more of a consensus that those animals may have actually flipped the switch, and genuinely have been generating heat internally and not just relying on external sources, or sources of heat generated through bodily processes. So it seems more likely that these small animals that are very likely built they look like they're built for an active life. Some of them have quite large brains. and large brains also demand quite a lot of fuel to keep them running. So dinosaurs might have actually occupied a spectrum of body temperatures and ways of maintaining those body temperatures, which might not be too surprising. I mean, we think of mammals as warm blooded. But some mammals run on a very low thermostat, things like sloths, almost picking up almost doing nothing in terms of their metabolic rate, they're relying a lot on external heat, they're not particularly active. Whereas other animals that we think of like nice, obviously, you're running on a very high thermostat running around constantly using up energy. So it might not be that surprising that when you have a range of animals that range in size, and range in behavior, that maybe they have some different strategies. The one thing I think we all agree on is that dinosaurs are all running warmer, on average, and probably keeping those temperatures constant. Unlike things like crocodiles, and turtles and lizards today.

Nick Jikomes 1:01:01

So So as a general rule, metabolic growth rates were higher for dinosaurs than living reptiles. So somehow, somehow, their metabolism and their physiology had to support that. You also mentioned something that I wanted to get to, which is, many of them had large brains. And you know, it's very interesting to think about things like what the cognition of some of these animals would have looked like, if only because they were around for, you know, more than enough time to evolve sophisticated cognition, potentially, I suppose the the reality that you're anchored to here is in looking at things like skull volume, and brain skull to body size ratios and things like that. What were some of the the more impressive dinosaurs looking like in those terms?

Paul Barrett 1:01:50

That's exactly right. So we're relying entirely on those kinds of measures when we're coming up with our ideas about how smart a dinosaur might be. So a lot of dinosaurs frankly, are not very smart. They have brains that are about the right size, for their body size. And they're not that much different from the kinds of relationship we'd see in a living reptile like Commodore or turtle. But there are a small number of dinosaurs that are on their way to being birds, that do substantially increase their brain size. And in particular, there's a few few things that are very close to bird origins animals called Peruvians. That include, for example, things like true or done, and to some extent, things like Velociraptor, where their brains are larger than we would expect for their body size, which suggests that these are animals that might be doing something different cognitively to the other bigger animals that are largely just using those brains to find other dinosaurs avoid being eaten and making other little dinosaurs. So these are animals that potentially might have been capable of flight. In most cases, behaviors, for example,

Nick Jikomes 1:02:57

I see. So they deviate somewhat in their in their brain to body ratio from other dinosaurs. But there's, there's not some species that's like off the charts.

Paul Barrett 1:03:07

Now, we're not looking at any of that arctic, when we don't have any source, extinct dinosaurs that we think of as things like dolphins. But of course, when we think birds into the mix, we do start to get contenders for really smart animals. convergently achieving in some cases, mammal like levels of cognition and ability in terms of things like to use a memory. So things like Corvettes, for example, crows are well documented told us as they, they are also proven to have good spatial memory and problem solving abilities. Parrots also known to exhibit some of those tendencies. So dinosaurs did get there. It's just they had to wait until birds for really for that intelligence, if you'd like to really take off punkers off as they're flying as well. But it is interesting that we do get that convergent evolution of those enhanced cognitive abilities in those two great groups, mammals and dinosaurs. And they often end up being used for the same thing and tool use and social communication and all these kinds of things. So when you're, if you're looking at a crow, you're looking at probably the smartest dinosaur that ever lived.

Nick Jikomes 1:04:25

So you did mention there velociraptors and some of those related species. Now, as I, as I'm sure you you have seen the popular depiction of the last chapter in the movies was a it was a predator, obviously, but B it was highly intelligent, and C It was social, so they hunted in packs. The last question is probably answerable in principle, right. Were there any VelociRaptors or predatory dinosaurs that were social and potentially pack hunters like that?

Paul Barrett 1:04:54

It's been suggested they were the evidence a little bit equivocal. So part of the evidence comes from finding groups have the things fossilized together. So there are a couple of examples of meat eating dinosaurs, found in small groups that are interpreted as packs that were wiped out in a single event. So that's one line of evidence. Another line of evidence comes from looking in the opposite direction that kills. So at herbivore skeletons that have evidence that they have been predated by more than one individual, because say there are teeth of different sizes left at the kill site. So that's the flip version of that. And the and the third part of that argument would be footprints, because there are again, some examples of footprints of meat eating dinosaurs, apparently walking in the same place together at the same time. And the final part of that would be, again, this idea about increased cognition that you might expect in an animal that's having to coordinate activity as a group. And that goes along with things like these small meat eating dinosaurs having bigger brains than we might expect for animals of their size.

Nick Jikomes 1:05:58

Interesting. And I suppose this is as good a spot as any I have to ask about T Rex. So what would you say if you had to summarize T Rex for us? When was that creature around? And what? How does what we actually know compared to what some of the popular depictions have been?

Paul Barrett 1:06:21

Okay, so T Rex was actually around a relatively short time, it's one of the last dinosaurs to evolve before the massive meteorite impact came along and wiped them all out. So it's on Earth for about 2 million years, it lived exclusively in what's now western North America. So it's known best from places like Wyoming, Montana, slightly in southern Canada, and down a little bit further down the Rockies. But that kind of central Rocky Mountain region is where most of its fossils come from. It's still one of the largest land based premises that we've ever found of all time, the only other contenders are other meat eating dinosaurs. And there's a little bit of argument over which was the heaviest and which is the longest. But T Rex of the ones we know about T rex is by far the best understood, because it's known on the basis of about 35, or 40, skeletons in museum collections around the world. So we know a lot about the anatomy of T Rex, what it was doing. And because it's such a popular dinosaur, not only with the public, but also with a lot of paleontologists, it has been worked on a lot. So every new technique that ever comes along, that needs to be applied, it very frequently ends up being applied to T Rex first, partly because people like it. And partly because there are lots of specimens of T Rex that you can get a decent sample to actually try these ideas out. So it's definitely an impressive animal up to 12 and a half meters long, about six and a half tonnes in weights, the top predator of its time. And in general, probably one of the most iconic dinosaurs in terms of its public can Pattu.

Nick Jikomes 1:08:01

What what do we know about you know, was that was that a social pack Hunter? Or are they solitary? And then of course, I want to ask about the famous tiny arms and and what we know about those.

Paul Barrett 1:08:17

So T Rex, we don't know too much about its actual social behavior. Most of your skeletons are found on their own. So it's been suggested that because of that observation, that they may be mainly solitary animals, we and we also know very little about T Rex growth. Actually, there are a couple of juvenile T Rex skeletons. We don't have any babies, we don't have any eggs, which is slightly unusual given that we know so much else about the adults of these animals. We also know for example, it grew very rapidly we all dinosaurs grew fast T Rex had this amazing teenage growth spurt, where it put on most of its weight in a very short period of time. So it's probably a loner. As far as we know. At the moment. There's a little bit of debate at the moment whether T Rex was feathered because earlier ancestors of T Rex did have feathers on the basis of known fossils of those animals from China with feathers on them. But the few bits of fossils skin we have from T Rex are all scaly. So it's not clear if T Rex had like a patchwork of feathers on some parts of its body and scales on others, which is entirely possible. Or if for example, maybe T Rex lost its feathers, which is also possible because it was a very large animal, it might have lost them in the same way that elephants have lost hair. So to avoid overheating. So even that fundamental aspect of T rex is actually something we were not quite sure about the moment despite the fact has been so extensively studied. And similarly that brings us on to the arms. I mean, there's silly arms. These things are. This is an animal that's 12 and a half meters long. It has an arm the same size as mine, and it's reduced its hand down very famously from the three fingers We normally see in a meat eating dinosaur just down to two. But that although it's very small that arm it's also very heavily muscled, it still has a lot of the big crests and processes on the bone for attaching large chest muscles to. So we really have no idea, the hands, the arms aren't long enough for the arms to reach the hands, when the animal is walking along its head is a long way in front of where its arms are. So it's not using them to reach out and grab things. It's primarily using its head to grab things in much the same way that a big predatory bird would these days. So the only remaining suggestion why people are suggested they have these teeth in the answer is that they basically evolved to not use the arm so much for pre GAAP capture. Maybe as a result, during evolution, because those features haven't been used very much. They've basically reduced in size, but they've kept some function. And the one function that everyone thinks it might be for is obviously the routers function, which is it's something to do with sex. And it might be basically so that male T rexes or female T rexes can get a good hold of the other partner during sex. And that's about the only expert sort of functional explanation for those things that isn't we can't reject almost everything else that people have come up with, there's a good reason why it probably wouldn't have worked. And this is about the one thing that still keeps coming back as being a possibility for Whitecap those arms. So the other, I mean, the other possibility is actually that if T Rex had been allowed to evolve for another 2 million years want to go may have lost the outs. Yeah, I wish we will never know, unfortunately.

Nick Jikomes 1:11:32

So the big topic that I think we're about to come to is okay, we kind of we've kind of done a little tour of the Triassic into the Jurassic. And in the Cretaceous, you've mentioned that the Cretaceous has the highest, the most impressive probably volume and diversity of dinosaurs, potentially, because the fossil record is biased in certain ways. And that's the earlier time that that's easier to see, potentially, also that it actually was the the most voluminous period of dinosaur existence. But then, of course, we're going to get to the famous Cretaceous extinction. So rough, all I know, is probably what, you know, close to what the average person knows, which is the obviously went extinct. There's the famous meteor that crashed into what is now present day Mexico. Can you give us a sort of updated version of what paleontologist think about in terms of that mass extinction event? Was it largely due to that Meteor? Were there other factors? Was it relatively sudden or more gradual than we might think? What did that look like?

Paul Barrett 1:12:33

So topic of dinosaur it's been really debated over the years, and there used to be strong camps, talking about how quick it was, how slow it was, and something like 80 to 100 different theories have been proposed for why. And most of those theories are very dinosaur specific. But what of course, what we're looking at is, it's not only does it went extinct at this time, but many other groups of animals and plants disappeared as well. So any mechanism that we come up with has to account for the mass dying off of all those other animals in land and see not just dinosaurs, so that helps narrow the field. And there have been two or three serious contenders for what caused this mass extinction over the years. Up until about 30 years ago, 40 years ago, they mainly came down thinking about gradual climate change, because the dance of the continents is still continuing on the Earth's surface, global climates are still cooling, vegetation is changing. And it was thought that those environmental and geographic changes might have been driving a long, slow burning, extinction. And other idea that came to prominence was in central India, we see evidence for two or 3 million years worth of extensive volcanism of lava is pouring out forming what's called the DICOM plateau in central India, putting down several kilometers thickness of rock over that period of time, associated with outgassing of lots of sulfur dioxide and carbon dioxide, which would have had an influence on global climates. These eruptions are happening at the very end of the Cretaceous. And the timing of that was suggested to some people to that in the 1980s. We have the impact hypothesis coming out where it's realized that there is this thin layer of rock in various parts of the world, at the very end of the Cretaceous period that is enriched with a rare element called Iridium that is very rich in meteorites and very rare on Earth. And that idea of proposed paleontologists in the street don't like it very much. And they say, well, we don't don't really like astronomers coming and telling us what to do. And not only that, where's the crater? And then 10 years after that the crater is discovered buried off the sea in the Gulf of Mexico, and actually had been found many years previously by geophysicist looking for oil, but hadn't realized that it was the age that it was and then workers gradually fine tuned our knowledge of the age of that structure. And it did infinitely coincides with that last day of the Cretaceous. So if you like, it's that hole in the ground is marking the end of the age of dinosaurs and the beginning of the age of mammals.

Nick Jikomes 1:15:11

We call that what's that crater called?

Paul Barrett 1:15:14

It's called, The chicks look closer, which is named after the village in Mexico, which is closest to the center of the impact site. So if you've ever been lucky enough to be on holiday in Mexico, and if you've Swami the so notae, you have swum in a piece of in a fracture that's there because of that crater. That Crater Lake structure that is huge extends over many 1000s of square kilometers of the seabed, and it makes it up onto the land as well. The rim of that crater is basically a fracture zone of rock. And that fractured zone of rock meant that the overlying rocks that came later became deeply fissures and cracks as a result of that process. So if you if you're lucky enough to go and swim in a snow, say, in Mexico, you're swimming in something that's only there, because a giant rock from space created a great big crater, 100 kilometers or so away.

Nick Jikomes 1:16:10

I see. So it's fair to say that that was a major key event in dinosaur extinction. But there were these sort of other things going on at the same time that were maybe happening at a slower pace that were contributing as well.

Paul Barrett 1:16:22

That's right. And there's been a very recent work using sophisticated ecological models. And also computer models for global temperature and the effects of the impact and also of the volcanic action, have now very firmly suggested that the vault the impact was the key, it was the only thing that was probably capable of creating the climate habit that took place afterwards. Whereas the volcanic action bizarrely, might have actually made the global situation slightly better than if it hadn't have been happening when the impacts happened. It looks like the meteorite impact led to a substantial period of global cooling. And it could be that the volcanism that occurred in India at about the time actually helped buffer though a bit of global warming, and it might have buffered it just a little bit. So the extinction may have been even worse, if it wasn't for the fact that there was also this extensive volcanism going on at the same time. And it's not clear if that volcanism and the impacts are linked. It has been suggested that by whacking the fast moving objects into the earth that may have in some way triggered this volcanic activity. But that idea is very much unproven at the moment, but probably unrelated.

Nick Jikomes 1:17:38

So this extinction event, is it accurate to say that this extinction event killed all of the non avian dinosaur lineages off. And the only dinosaurs that survived are the direct body birds, or the direct descendants of those lineage all the dinosaur lineages that actually survived this thing.

Paul Barrett 1:17:59

That's exactly right. So that nothing as far as we have never found the fossils of a dinosaur in rocks that are younger than that event. So that's slightly untrue. There are one or two fossils, but these are fossils that are reworked, these fossils have been eroded from older deposits, and then brought back in as pebbles essentially, so but no dinosaur fossil found in the place where it died, as ever been found above that layer. And similarly, it wasn't only dinosaurs that were so some types of birds also died out and never made it past the boundary. Some types of mammal didn't survive past it. Many different types of marine invertebrate and micro microfossil also never made it past that boundary. So altogether, it's something like the estimates are between 60 and 70% of all animal life, became extinct in that very short interval.

Nick Jikomes 1:18:57

Interesting. So various bird species, also an extinct at the time, as you mentioned, mammals as well, the image I have of mammals that were around concurrently with dinosaurs. I'm not sure if this is a caricature or not, is that they were mostly diminutive creatures that they were small, nocturnal, rodent, like things that, you know, couldn't compete in various ways with what what else was, what the dinosaurs were dominating the earth. But then it's after this extinction event that you start to get this massive radiation. So what did mammals living at the same time actually look like? Is that an accurate picture that I just painted? And then what does that mammalian radiation look like? And when does it actually start to happen?

Paul Barrett 1:19:41

So you're right. The majority of mammals are alive while dinosaurs right most small, the largest mammals that were around were no larger than a house cats, maybe getting up to the size of a raccoon or something like that. So they were all small, most of them would have been superficially very rodent or shrew line. squirrel like, but they did have a wide variety of lifestyles, some of them are scampering along the floor, some are living in trees. We even have some of these Jurassic and Cretaceous mammals that have adaptations for swimming and for gliding. So there are lots of different lifestyles, but they're all relatively small animals and relatively unobtrusive in terms of if you turned up on in your time machine in the Cretaceous, you wouldn't necessarily be the most obvious animals in the landscape. So they are around, they're quite diverse, but they're certainly not ecologically as important as the dinosaurs that are around at that time. Although there is one my fossil mammal colleagues do like to point out there is at least one of those larger, early mammals, that it's fossils were found with the fossils of dinosaur babies in its guts, so that they did get one back. Where they have one animal that did feast on baby dinosaurs, no, probably others. But what happens when the dinosaurs disappear is we end up with a vast amount of empty ecological space on land. For different roles that dinosaurs occupy, there's top predators, and there's big herbivores, all of those kinds of slots are empty. And in the recovery periods, we start to see other animal groups starting to take over those roles. And that recovery actually takes some time. It's not instant, it takes a few million years for these different groups as themselves start radiating evolutionarily into different ways of life and things like that. And actually, initially, birds initially did quite well, for example. So we this is a period where we see some parts of the world the top predators were actually large, flightless birds, almost in a way recapitulating what the meat eating dinosaurs were doing before the impact hit. So there's just this brief period where we see some of those ecosystems actually, the top predators aren't big, ferocious mammals, but they're rather big, scary looking birds. But eventually, mammals do come to occupy almost all those niches that dinosaurs occupies. But interestingly, all through the history of the remaining history of life up until now, although mammals became very diverse, they, they re invaded the seas. So we have things like whales, we have bats invading the air, we have primates becoming very smart and eventually leading to humans. They never approached the same kinds of sizes on land that dinosaurs did. So although whales are larger than dinosaurs seems like the blue whale is as far as we know, at the moment, the largest animal that's ever lived. But as I'm fond of saying, whales, cheat's, whales live in water, they don't need to hold their weight up against gravity. And they basically swim around with their mouths open and eat a very rich food source. Whereas gigantic dinosaurs work for a living because they had to hold their bodies up against gravity. And they did that by eating a very poor food, the source in order to do that. And when we look at land living mammals, they don't even begin to rival the large, just dinos inside large land animal mammals top power about 15 or 20 times with some of these extinct very large relatives of elephants and rhinos. But we haven't found anything bigger than that. Whereas the largest dinosaurs that we know about, are weighing up 60 or 70 tons. So at least three or four times more than the largest mammal ever.

Nick Jikomes 1:23:28

And what are those are those like the Brontosaurus type things?

Paul Barrett 1:23:32

That's exactly right. These are animals that we call technically called sauropods, the very large, barrel bodied animals that are four legged with very long neck one side and very long tail. And the largest representatives in that group are things called titanosaurs, very appropriately, and they get up to as far as we know, they get up to about 65 to 70 tons in weight. So we're looking at something that's the equivalent of about 10 African male elephants on the scales.

Nick Jikomes 1:24:01

Well. So the dinosaur extinction is, you know, probably the most famous and dramatic mass extinction, not only because it's the dinosaurs themselves disappearing, and they were so impressive as animals, but because you've got this relatively, you know, sort of clean story that involves this meteor crashing into the earth, if we think about that mass extinction that actually enabled the dinosaurs to to radiate all over the globe. Or we think about other mass extinctions that perhaps you could talk about, do they all tend to have at least one large ish precipitating event? Or are there some that are, you know, much more gradual in nature? What is there any pattern to mass extinctions look like? Are they all kind of unique events?

Paul Barrett 1:24:50

They're all they're all kind of unique. So for example, the one at the end of the Cretaceous is the only one that we are convinced is related to an extra terrestrial impacts. So some of the others there have been suggestions that there might be evidence for a meteorite hitting. But only convincing one for that gigantic rock from SpaceX donation so far is the one at the end of the Cretaceous period. The one defining one of the defining features of mass extinctions is that they're relatively rapid geologically. That's how we recognize them. They're in times of great dying in a relatively short period. So they're all usually quite quick. But they do seem to have different mechanisms. So for example, we have the meteorite impact for the end of Cretaceous. But the the largest mass extinction of all time, which happens prior to the origin of dinosaurs occurs at the end of the Permian period, which is the one immediately before the Triassic, about 250 billion years ago. And this is was a devastating extinction, which wiped out almost all life, like 97% of all marine species are thought to have died during this relatively short interval. And that extinction seems to have been caused by massive volcanic activity in what's now Siberia, there are these huge areas in Siberia, known as Iberian traps, which represent millions of cubic meters of lava that was spewed out over a relatively small period and a long area. And it's still that the climatic and chemical changes that they cause to the biosphere, destroyed ecosystems, and then we have a long period of recovery from those changes there. So actually, volcanism has been implicated in at least two of the big three extinctions, once at the end of the permanent, the really big one, and then once at the end of the Triassic period, when dinosaurs kind of managed to take over. And so those two extinction seem to be very closely related to volcanism. The one that wiped out dinosaurs is something to do with a giant rock from space. And then there are extinctions again, which are either linked with climate, or whose causes aren't yet quite yet now, there's still argument over what the actual physical cause was.

Nick Jikomes 1:27:06

And so on the topic of volcanism, how are we living right now through a very quiet period of geological time in terms of volcano activity, the time that humans have been evolving inside of or, or not,

Paul Barrett 1:27:25

it's at the moment we're living through a relatively quiet period in terms of what's going on. So these major volcanic events that caused these extinctions are caused by what are called flood basalts. So these are when there is a large amount of tectonic activity and active movement of plates away from each other an upwelling of huge amounts of lava from the interior of the earth to create basically new land, or new areas. And these are things that are driven potentially by cycles within the interior of the earth. Again, this is debated area, and I'm not a geophysicist, so I'm not going to try and explain the reasoning behind them. But it is suggested that there are cycles of assembly of reassembly of the continents that are going on over a very long extended time periods. And these are in some way linked to these pulses of volcanic activity. There are also lots of random events where we just get blobs of superheated lava coming up from closer to the Earth's core as what's called a hotspot that can get to the Earth's surface and be a focus for and in an intense or ongoing period of volcanism. So for example, on a much smaller scale, the Hawaiian Islands are caused by the Pacific Plate moving over a hot piece of mantle underneath it. And as that plate moves over, that hot piece of mantle occasionally punches through and makes a volcano and makes an island. And as that plate keeps moving over it, and the eye and the islands move away from the hot suppose of volcanoes become less active and eventually switch off. So the Hawaiian Islands formed in that way, the Galapagos Islands formed in a similar way. And that's a relatively small scale, one of those events, large scale events or things that might have led to example to the North Atlantic and the South Atlantic and other really big ocean basins. So the the moment, I think we're lucky in that we're living, we're not living in one of those times, because and otherwise, when even worse climatic trouble than we are already.

Nick Jikomes 1:29:33

So you may have touched on this a little already. But when we talk about the dinosaur extinction from the meteor impact at the end of the Cretaceous, we talked about that being a sudden event, but of course, we're talking about geological time, here remind me like, What is that window of extinction? Is it literally like, you know, within a few years, it disappeared, all those non avian dinosaurs or is it like a 2 million year window or something like that?

Paul Barrett 1:30:00

We're talking about something within political time. So we're talking about something that's happening depending on the animals or plants concern, things are disappearing over the scale of months to decades. So this is a very, very short period of Earth history, we're not talking about things hanging on for a few million years, we're talking about things within real ecological time being wiped out. And that's because we think a lot of the mechanisms involved in killing these animals are things like starvation, which are literally wiping out populations very, very quickly. So it's notable that a lot of surveys of that event animals, or plants are either generalists. So they're able to switch their diets, they're able to switch their habitats, they're able to move away from areas that are bad, or the specialists go, or they're things that potentially were able to be effectively dormant for a while. So seeds, for example, spores that can lie in the ground undisturbed, potentially for many years, and then be rejuvenated when conditions are better. So this would have been a devastating time. And I think a lot of the certainly areas around near the impact. So in northern South America and the sub south, eastern US would have literally been devastated it would the scenes would have been apocalyptic, you would have had rainfall of superheated rock, you would have had tsunamis sweeping over the land surface, it would have been a really horrible day to be on holiday around the Gulf of Mexico. And even on the other side of the world, I mean, the about the safest place to have been at the time would have been New Zealand, which is about as far away as you can get from where the meteorite hit. Even there, there's evidence of that event, because we see that same layer enriched in this rare element of radium being laid down in that part of the world too. And the animals or plants in that region are also suffering. So this is genuinely a global event. But obviously, would have been instantly devastating for the animals within potentially 1000s of kilometers from where it took place. And then the longer term effects of that happening would have spread around the world quite quickly, leading to this more kind of potentially month to decade long decline in those other groups.

Nick Jikomes 1:32:23

We've I mean, we've we've really focused on the natural history here. We of course, talked about the earliest dinosaurs. I'm also curious, what was the earliest dinosaur fossils discovered? What species was it? And where did that happen? What sort of kicked off the entire field of understanding dinosaur? Dinosaur? I

Paul Barrett 1:32:42

mean, in terms of the the history of discovery,

Nick Jikomes 1:32:44

yes, the history of discovery was the first dinosaur discovered. When did that happen? And where was it?

Paul Barrett 1:32:49

Sure. So actually, this, as far as we know, in terms of documentation, this happened in Europe, it's entirely possible that lots of people around the world were encountering dinosaur bones and finding them and being curious about them, maybe even incorporate them into their rituals or their belief systems. But in terms of actual written definite evidence of dinosaurs, it dates to the 17th century in Europe, where we have first of all, first books, mass produced thanks to the invention of printing press, and a widespread interest in natural history by those people that actually had the time and the kind of privilege to be able to sit down and think about things so often people who were because in country pass, in kind of country, parishes and members of the aristocracy had lots of money and time, were able to be curious rather than having to do things. So the first illustration of a definite dinosaur fossil, but we're aware of, is in a book by a guy called Robert plots, who illustrates a, what we now know is the end of the thigh bone of a meat eating dinosaur from the Jurassic of the UK. He didn't know what it was when he found it. He thought about a lot he initially thought it might be from a fossil elephants that were maybe been brought over by the Romans to the UK when they were in there. But very famously, he then decided for a slightly broader interpretation of thinking that it was actually a giant fossilized human scrotum. It has a very distinctive shape, which may have led him to that conclusion. But it's very definitely the knee joint other dinosaur. And so this was actually formerly named Scruton Humana, Robert, and Robert plotz book, and there are also a number of other books published around the same time that figured what we think are probably dinosaur teeth. Also from the same, the same Jurassic rocks in the UK, so that they weren't recognized as dinosaurs at the time. They were just curiosities. No one really knew what they were. And it was not it had to wait another 100 years or so. When more of these bones, these bones were being found, they were being talked about, but nobody had really idea of what they were. And in 1824, a clergyman at Oxford University, William Buckland, published his research on set of bones found just outside Oxford, and published the name Megalosaurus, which is the first dinosaur name to have ever been formally proposed. And that was based on a series of bones from rocks about 164 million years old, just outside Oxford. And that really kick started dinosaurs as a subject. So that was the first one to be named, was named in the UK, the next two to be named, but also found in the UK. And then a few more came in from continental Europe. But again, although these things were being named, they were recognized as joint extinct reptiles, but it wasn't thought that they belong together, or they might be related to each other. And that insight came in the 1840s, with the British comparative anatomy, Mr. Richard Owen, who realized that a lot of these fossils had things in common, that link them together as a group, and that those things were very different from the features seen in living reptiles. So he was the one that coined the name dinosaur, in 1842. And recognize them as a distinct group of animals.

Nick Jikomes 1:36:16

I see. So we know for sure that people were finding what we now know, were dinosaur fossils in the 1600s. But it's not till the mid 1800s, that people had a conception of the dinosaurs that we read that as we recognize it today.

Paul Barrett 1:36:30

That's exactly right. And that comes down to the fact that it took a long time for people to accumulate the kind of knowledge to see what they were looking at. So during that time, they become a greater appreciation of the age of the Earth, a greater appreciation of the structure and range of living animals, as people started to investigate the animals around them in a more systematic way to, as they say, it's almost certain that people are encountering dinosaur fossils around the world. Yeah, I'll put before that. But these are the first times that they're recognized as such,

Nick Jikomes 1:37:03

are there any hints of what you just mentioned? So for example, you know, I can imagine, you know, going back as far as we might imagine, you know, some indigenous group living somewhere encounters a T Rex skull or encounters some other impressive dinosaur specimen. And perhaps that is artistically represented in some kind of artifact, are there any hints that maybe something like that once happened,

Paul Barrett 1:37:27

there have been some suggestions about this, some of which are actually relatively convincing. So for example, a scholar in the US called Adrian Maya has suggested that the Griffin myths that were very prevalent in the Middle Eastern in Europe in kind of from the Middle Ages, and Medieval Period earlier, may have had their origin by travelers encountering the fossilized skeletons and skulls of dinosaurs along the Silk Road. So as the, the Silk Road route goes through, a number of very fossiliferous parts of the world goes through Northwestern China, and through Mongolia and part on the steppes of Central Asia. And it was suggested that these animals in particular, which have very parrot like beats, and have hoof like claws on their feet, might have been a very good model for the kind of chimeric animal that that they came up with for Griffin, which obviously has the head of an eagle and the body of a lion, which actually is not a big jump of the imagination for a Protoceratops skeleton. So for example, that that myth of the Griffin might actually have its direct origin to the discovery of dinosaur fossils and an early interpretation of what they might be like. Other cultures unfortunately, generally don't have much written lack surviving written language. So and also a number of cultures in places where dinosaur fossils quite common. So for example, in the American West, didn't always have visual representations in their culture as well. They tended to be people that were often moving around people that didn't leave a lot of obvious depictions of things that were not highly abstracted, or that have survived at least. So there are very few records of what if you like pre scientific views of dinosaurs might have been but there are hints that people were interacting with them and didn't know about them. So I do a lot of work in southern Africa, for example, and some of the areas in which I worked some of the local people there, they know that these bones are in the ground. Some of those people don't have an idea actually what a dinosaur is, because just the way they've been just in the kind of way they've been brought up. They've never been encountered. The idea of them in the media they've been seeing or in the in the kind of communities they've been living in, but they do recognize them as the bones of animals, and they are often interpreted as Their belief systems as part of kind of an ancestral animals that were living in this area. So there's definitely a conception that these are animals from a deeper time than the time we're living in now. Different from animals today. Yeah.

Nick Jikomes 1:40:16

And that that does kind of make sense, because I think all human cultures have a very potent sense of ancestors, our own ancestors, but it makes sense that would be natural for them to think about animals that way as well.

Paul Barrett 1:40:29

So, so that there's clearly an appreciation of these types of objects and their interpretations of what they are. In terms of thinking of, if you like historical depictions of those bones, in art, or in other Korean kind of ritual contexts, I don't think there are any good examples that are definitely of dinosaurs. I think there are some examples of things like that from more recently extinct animals, things like mammoths and woolly rhinos, and so on. But dinosaurs not so far as far as we're aware. Another reason actually is a lot of the richest dinosaur grounds are genuine areas that are not particularly nice to live in. Yeah, they're dry, they're often difficult to farm, they might have low densities of gain. So they're not necessarily areas that they're that people were doing more than traveling through, rather than living in it very famously, for example, some people living in Siberia used to make their houses of mammoth boats. So they were using kind of those paleontological resources for a very practical purpose. And they were aware of the mammoths being frozen in the permafrost and made use of those resources in their day to day lives.

Nick Jikomes 1:41:46

So speaking of mammoths, or just the general notion of something that's more recently extinct, and therefore better preserved, I know that there's very, very good specimens of mammoths that are, I think, literally frozen and more or less intact, where you do start to get things like DNA. And you do start to ask these drastic park like questions about bringing a creature like that back is, is that possible with a mammoth or more recently extinct species? And do you see any scientific value in doing something like that?

Paul Barrett 1:42:17

Well, we have, because they're so recent, and times for us. And because they're so well preserved, we know a reasonable amount about the genomics of some extinct Ice Age mammals. So we have a reasonable amount of knowledge of the genome of Mammoth and woolly rhinos, and of things that are more recently extinct, like boas, and also even obviously, of Neanderthals, and some other ancient human species as well. So this has been an emerging field over the last 20 years, and there have been huge technical advancements that have allowed people to do that. And there are efforts underway in some parts of the world to try and recreate mammoths. So I know there have been serious efforts to do this in Russian laboratories to do to use what we know about mammoth genetics to use a, I think, using an Indian elephant surrogates to try and bring mothers back. And the reason for using an Indian elephant is that they're actually off the two living elephant species. They're the closer relatives to mammoths. So before that, they have a higher chance of success. So one of the key technical barriers to doing this actually is not so much knowing about the sequence of mammoth DNA is to know more about mammoth pregnancy. And indeed, the pregnancy of living elephants, which there's a lot of work that still needs to be done on the basic physiology of how elephant pregnancy works that you'd have to solve before you can even then start to think about the next step of cut using one as a surrogate for cloning a mammoth. So there have been attempts, I don't none of them have been upheld at any success at all at the moment. And I can there I think I have a couple of conflicted idea about whether this is a good idea or not. I think one of my it's not me, it's it seems increasingly clear that Manus became extinct because of natural climate change. Humans may have helped hasten it along. But they were adapted for a much colder world and that cold world is got. So it's not simply that they were hunted by voracious packs of other humans desperate to kill every big hairy elephant that they ever met. It's actually because the ecosystems a left in contracted in size and ultimately vanished. So we would be bringing back an animal if you like that would not necessarily be a good fit for the ecosystems that are in those parts of the world. Now, I could be wrong. It could be that they would actually thrive in those ecosystems, but they were animals that actually have no, not much of a moral responsibility for it. their disappearance, these are things that are generally probably doing quite badly because of natural causes. So I don't think there's necessarily a strong moral case that we should bring some of these things back because we are involved in their extinction. And in fact, the moral case then is are you bringing these animals back into an unfamiliar world where they're going to be stressed? So it's, for me, it's a, I really like the idea of mammoth steppe coming back. And mammoths were amazing ecosystem engineers, they used to keep those environments free of trees, they used to basically cultivate those areas to suit themselves by transporting seeds around and fertilizing them with their dung and all those kinds of things. And it would be amazing to see them roaming about again, but we probably kidding ourselves, if we think we're recreating the primeval state of those areas, simply by putting a few genetically engineered mouse back in. I think, if we were going to make a moral case of it, there are cases of animals that we made extinct more recently, through hunting or through habitat destruction. And I think things like the idea of trying to use genetic technologies to save animals like, say, the northern white rhino, potentially, quite morally praiseworthy. Whereas the things that have been long extinct, the moral question might be the other way around in the sense that I'll be bringing animal or not adapted to the environments that are around now. And in fact, creating stress for them, and potentially stressful the other animals that do live there now that aren't used to being around. So it's some interesting moral questions to throw around, as well as the very real technical questions involved in doing that kind of work.

Nick Jikomes 1:46:44

What I'm, very briefly, what's your own origin story? As a paleontologist, were you just, you know, a little boy who loved dinosaurs and just stuck with it? Or did you get into paleontology somewhat later in life?

Paul Barrett 1:46:59

I was one of those individuals that started design cells at the age of six. So my mom brought me the Ladybird book of dinosaurs. And I took from that point onwards, I was always very keen on the history and science when I was a kid and growing up, and I various times when I thought I might try and do other things, I thought I might be an astronomer at one point. And then I realized I wasn't interested enough in maths to do that. Another point, I thought I might want to be a veterinary surgeon. And I realized I wasn't interested enough in animals biting, biting me when I was trying to look after them, or accidentally dispatching them on the on the table in the surgery while I was trying to do my best to care for them. So eventually, the idea of dinosaurs was always been with me became the most attractive one. And that's partly because I am still very much interested in living animals as well. And dinosaurs were amazing animals. And studying them means that not only are you thinking about really cool animals, but you're also doing a lot of problem solving. And I like the kind of detective work that we have to do to use the incomplete evidence that we have in order to build pictures up. And that kind of combining lots of different lines of evidence, and looking for patterns and trying to come up with the cleverest deductions from the least amount of evidence is very appealing.

Nick Jikomes 1:48:26

A couple of quick questions about present day paleontology. One is, you know, I would love to just know, very briefly like, what are a couple of the hot topics right now that you know, paleontologists are really keen to work out that we think we're going to solve but we haven't figured out yet. And to, how many of you are there? Are there like yearly paleontology conferences? Where 1000s of people are getting together? Or? Or is it a few dozen individuals who are like the big thinkers.

Paul Barrett 1:48:56

So if we think about paleontology as a whole, so everything to do with the history of life, there are lots of different questions to do with the different groups of animals and plants around us. I would say one of the biggest areas that people are working on at the moment is trying to get as much evidence from the fossil record as possible to know what we might face in the current climate crisis. So obviously, through the extinction of life, we've seen different groups come and go, we've seen them expand the contract and their geographic range, because temperatures have changed, the amount of rain has changed, geographies changed, and what a large number of us are doing are gathering those data to see if we can baseline the kinds of natural changes we've seen in the past. And what happened during those periods of change to give us some idea of what might happen during the current accelerated period of change that we're seeing now, due to human impact on the environment. So a lot of my colleagues are working on questions related to that and particular colleagues that work on for example, microfossils, which had these very, very detailed long term fine grained records of response To change key and working out what some of the things are. And similarly, I mean, I although I work on dinosaurs, which had relatively little to do with that question, I've also worked, for example, on fossil turtles, where we can look at what turtles have done through time in response to different climate shifts, and actually use that to predict what living turtles might do in a warming world. So a large amount of the effort in paleontology as a subject is going towards that. And I would say, there's also, if you like, the traditional strength of paleontology, but still continues a lot. It's also just trying to work out how the major groups of animals and plants are related to each other. And what that pattern of life overall looks like to work out. Is life increasing in diversity all the time? Does it go through highs and lows? How quickly? Do we get new biodiversity being generated? Those kinds of questions? So those are the really big questions in the subject. And then that's a smaller questions that we do day to day like to do with the lifestyle of the animals or plants to do with their detailed anatomy to do with how they're related to each other.

Nick Jikomes 1:51:11

And how, how big is the field of paleontology generally, is it 1000s of individuals and hundreds?

Paul Barrett 1:51:18

I think when we take all paleontologists around the world into consideration, we're talking small 1000s. So for example, the biggest convention in vertebrate paleontology, so dealing with fish, amphibians, reptiles, holes in the world, routinely gets about 1000 delegates each year, which is about 5050 students and 5050 professionals. So in turn, and in terms of the people that work on dinosaurs around the world, people that are actually in tenured permanent jobs, I would say there are probably about 200 of us, around the world spread almost internationally, with large concentrations in the US and Canada and Argentina and Western Europe. But there, there were enough of us that we more or less can know everybody by on first name terms.

Nick Jikomes 1:52:14

What, um, you know, just very broadly speaking, in your entire career, everything that you've learned you thought so much about natural history and things in the past and extinctions and radiations? What kind of perspective has that given you about the present moment for humanity?

Paul Barrett 1:52:33

I think one of the things it gives you is a certain sense of hubris, like we actually see through the history of life groups becoming unbelievably successful, dominant. And then for reasons beyond their control, they just disappear really quickly. And I think that tells us a really strong story that when we are smugly sitting thinking we're pinnacles of creation, that actually, we haven't been around that long. And we're relatively fragile in ways that we probably don't appreciate in terms of these great planetary kind of crises. And as a result, it gives a sense, it does give you a slight humbling sense to know that things can go drastically wrong really quickly, even if you think everything is actually fine. So I think that sense of a general sense of how fragile life is, is something that comes out of thinking about that very long term perspective, but more positively. The other thing, and it sounds terrible, but it genuinely gives me a kind of warm glow is actually the interrelatedness of life. Like we share so much in common with other species, we share their environments, but we also share their DNA. You can't see it, but where I'm sitting at the moment, I have a houseplant a couple of feet from me. I mean, I share a lot of my DNA with that plant. We all have a single common ancestor going back years and years we have a single common ancestor with apes. We have one with other mammals, we have one with other things that lay eggs, we have ones with other things with backbones going back and that connectedness is actually a really positive feeling that you're part of this kind of greater and really complex whole

Nick Jikomes 1:54:20

final question. Drastic Park great movie, or does it just irritate you?

Paul Barrett 1:54:29

I actually great movie. I really enjoyed it. So the original movie came out when I was still an undergraduate student. I went see it immediately when it came out. And I also have very warm feelings about it because it actually got me my first paid job in paleontology. I ended up being hired as an intern for that summer when the movie was released to support a colleague of mine who needed someone to help field all of the inquiries they were getting that summer. So I'm naturally very inclined to have warm feelings about it because I actually had my As a result, but generally I think it's a great movie at the time, they did work very hard to try and make the animals look like really good living, breathing animals, they took it seriously. And the premise of the story is a really clever one idea of getting DNA out of mosquitoes and cloning dinosaurs. It's, unfortunately, technically almost certainly impossible, at least at the moment, and probably quite probably never will happen. Probably shouldn't either. I mean that the movie itself says we really shouldn't do this. It's just done. Right. But the idea is quite elegant. And in terms of getting people interested in the subjects, it was an amazing ambassador. And for a lot of the things, some of my colleagues do get annoyed when they start presented, or they see things that are factually inaccurate. And you understand why because it's close to people's heart. But at the end of the day, it's a story. It's a movie, it's fine. You know, we know it's made up, it's not a documentary. So I think you have to keep those things separate in your head. And as an adventure movie, I think it's still a great movie. And I'd be lying if I said, I didn't watch it from time to time. I don't sit there watching it every week, we're in kind of an Alan Grant. But it's still a really, I think, a really entertaining movie. And despite all of the criticisms, you might have some of the content I don't think that takes away from the fact that it's a lot of fun.

Nick Jikomes 1:56:33

Well, Professor Paul Barrett, do you have any final thoughts on the general subject that that you might give to a general audience before we go?

Paul Barrett 1:56:41

I think one key thing say would be that Paleontology is actually one of those scientists where sciences where you don't need to be a specialist to contribute, it's still very much the case that if you're a keen fossil collector, and you have sharp eyes, and that you are curious, you can actually still make a contribution, you don't necessarily need a particle collider, or a lab or lots of expensive machinery, what you need are good eyes, and ability to walk around and spot interesting things on the floor. And they can still actually make really key contributions to the subject without formally and professionally being a part of it. So pay there is one of those sciences where we actually have a very strong amateur community that interacts very closely with a professional community and actually has very good relationship with it. So it is genuinely one of those areas where you can infuse people hands on, without having to go through extensive training or, or having to get expensive grants or fancy degrees, and you can still actually make a real contribution. And the other part of it is if you are interested in finding fossils, if you're the first person find a fossil, the first human that's ever seen that thing since it was buried, however many millions of years it was ago. And that's a moment of pure individual discovery, the likes of which a lot of people will never experience. You're literally seeing that insight into a vanished worlds. And you're the first person to see it. And there aren't many other people who get to that kind of thing. So that's a really fun reason to be a paleontologist.

Nick Jikomes 1:58:16

Professor Paul Barrett, thank you for your time.

Paul Barrett 1:58:20

No pleasure. Thanks very much for the invitation.

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