The Ancients - The Rise of Mammals

Episode Date: June 23, 2022

They survived extinction level events and record high global temperatures - how did mammals adapt and thrive in a dramatically changing world? In today's episode, Tristan welcomes back Professor Steve Brusatte to uncover the origins of mammals. Going back to a time before the dinosaurs, from lizard-like creatures to wooly mammoths, Steve helps us understand how so much is known about life 300 million years ago. For more Ancients content, subscribe to our Ancients newsletter here. If you'd like to learn even more, we have hundreds of history documentaries, ad free podcasts and audiobooks at History Hit - subscribe today! To download, go to Android or Apple store.

Hi, I'm Tristan Hughes, and if you would like the Ancients ad-free, get early access and bonus episodes, sign up to History Hit. With a History Hit subscription, you can also watch hundreds of hours of original documentaries, including my recent documentary all about Petra and the Nabataeans, and enjoy a new release every week. Sign up now by visiting historyhit.com slash subscribe. by visiting historyhit.com slash subscribe. It's the ancients on History Hit. I'm Tristan Hughes, your host.

And in today's podcast, well, once again, we're going millions of years back in time. We're covering millions of years. We've done the dinosaurs in the past and we will do dinosaurs again. We've done the origins of life too. But today we're talking all about mammals. Yes, that extraordinary species, us included, but we're going back, as mentioned, millions of years

to talk through the rise of the mammals, how this rise predates the dinosaurs. It predates the Triassic period, more than 252 million years ago. We're going beyond that. Then we're also going to go through the Triassic, through the Jurassic, through the Cretaceous. They managed to survive the meteorite extinction. Then this truly became the reign of the mammals when you saw these incredible, huge, large animals,

for instance, of the Ice Age, saber-toothed cats, woolly mammoths and so much more. We're going to be talking about all of that with a specific focus on the early rise of the mammals from pre-dinosaur to post-dinosaur because we've got the one and only, the best man for the job on this, none other than Professor Steve Brassati from the University of Edinburgh. That name might ring a bell for a couple of reasons. One, and of course the main reason, is because he's been on the Ancients podcast before. He was our brilliant contributor for the Rise of the Dinosaurs podcast, which we did a few months back in March time. But Steve, you might also know him from the world of film, from the world of stardom, because he's also played a role in the new Jurassic World film. Steve played a part in the creation

of that film. So he's riding high at the moment, Steve. And we also managed to get some of Steve's time because he has now written a new book. He has written a book all about the rise and reign of the mammals. So this seems like too great an opportunity. We've got Steve on the podcast today to talk all about the rise of mammals. So without further ado, here's Steve. Steve, it's wonderful to have you back on the podcast, my friend. I'm very happy to be back. So soon after the last one, we talked about dinosaurs recently, and now I'm very happy to talk about mammals, especially now with my new book on mammals, saber-toothed tigers, woolly mammoths, fossil humans. There's such an amazing story of

mammal evolution, and I'm excited to dive into it. Well, absolutely. You mentioned all those big words, saber-toothed tigers, woolly mammoths, and the like, but we did the rise of the dinosaurs last time. We're doing the rise of mammals now. If we go further back in prehistory, because mammals, they're the most beloved creatures today, aren't they, Steve? But when you look at the story of their rise from before the dinosaurs, during the dinosaurs, and after the dinosaurs, it's similarly staggering and extraordinary, isn't it? I think so. Dinosaurs get a lot of the attention. When it comes to fossils, extinct creatures, dinosaurs are the ones everybody talks about.

They're the ones that all the kids know. Everybody learns about them in school. They're the ones that are the superstar exhibits at all the natural history museums. And rightly so, right? I mean, T. rex, brontosaurus, these are amazing, fantastic animals. But the story of mammals is at least as fascinating as that of dinosaurs. I think more fascinating and certainly more relevant, more relatable, because this is our story. This is the story of our heritage. We are mammals. Of course, we're mammals. We have hair and we feed our babies milk and we have molar teeth and all these things that make mammals mammals. We are part of the mammal family tree. Our lineage goes back over 300 million years to the time that the mammal group split off from the reptile group

on the great family tree of life. And it has been a dizzy several hundred million years of evolution that has brought us to the world that we are in today, where we, a single species of mammals, Homo sapiens, have so much power, so much influence over our world. But of course, we are one of only 6,000 mammal species alive today. And we have so many different mammal relatives that are stunning in their own ways. And it bears saying biggest animals ever in the history of the world are mammals, blue whales, and they're alive right now.

So for anybody that thinks, you know, why is this guy? He studies dinosaurs. He wrote a book about dinosaurs. Why is he moving on to mammals? Well, mammals are us. It's our story. But if that's not enough, just imagine a world where blue whales are extinct. All we had were some fossil bones. They would surely be as famous, as iconic, probably

even more so than things like T-Rex. Let's go right to the beginning, the beginning of our story. The ancestors of the mammals, the roots of the mammals, as it were. What do we know about these early ancestors of the mammals? Where does our story really begin? the bifurcation of the family tree of life. You had two groups going their own way. You had the reptile group going one way. They would eventually produce crocodiles, dinosaurs, lizards, snakes, birds. And then you had the mammal group going the other way. Now, they weren't mammals yet. These were the deep ancestors of mammals. These are things that we call synapsids. And they were living back in the Carboniferous period of geological time, and this is the time of the coal swamp. So much of the world's coal was formed during this time because there were these jungles

that clung to much of the land. The land was much warmer, much wetter over much of the earth. And so you had these big trees. Now, these were not oak trees or maple trees or pine trees or any trees like we're familiar with. These were trees, the first real, true, proper, big trees in earth history. They stretched over a hundred feet into the canopy and they grew really fast, really, really fast. And then they would get buried by floods and turned to coal and a new forest would rise up. That's why you had so much coal. It was this hot, humid, swampy world with these enormous trees, dense forests. There were insects, dragonflies the size of pigeons. There were millipedes that were eight feet long. This was a crazy time in Earth history. And in the undergrowth, in the ferns that were in the bottom

of the forest floor, you had the first little synapsids evolving, the ancestors of mammals. And they were simple animals. They would have actually looked quite a bit like lizards if we saw one. They were not lizards, but they would have looked something like that. They would have been covered in scales. Their arms and legs would have sprawled off to the side. They probably would have been flicking their tongues, you know, like an iguana. But it was those animals that mammals came from. And the only thing that really set them apart initially is that they had a hole behind their eye socket. And that hole was where big jaw muscles attached. So these animals had really strong bites.

And it was from those very humble ancestors that eventually everything from woolly mammoths, whales, bats, saber-toothed tigers and humans would eventually evolve. I mean, Steve, it's absolutely fascinating. You mentioned how this is all over 300 million years ago and it really begs the question, first of all, how do we know that much, for instance, about the skull and all of that? How do we know so much about these synapsids, these very early ancestors of mammals? We know based on fossils. Fossils are our clues. They're the clues that tell us what used to live, where things used to live, what the earth was like during that time. And it's an analogy that paleontologists like me use all the time.

And I use it in The Rise and Reign of the Mammals in the new book. Early on, I say, hey, look, we fancy ourselves detectives. And we do. It's the reason a lot of us love true crime shows. And so me included, you know, there's just a real detective aspect of our work. And for us, we are always out looking for fossils, bones, teeth, skeletons, footprints, eggs, whatever it is, the marks, the remnants, the prehistoric life left behind, you know, similar to how archaeologists will look for human artifacts, how historians will go through manuscripts. It's that kind of thing. And so a big part of our job is going out and prospecting for these fossils, going out, whether it's into the Badlands, into the desert, a bluff behind a Walmart or a Costco or whatever, you know, wherever there's rocks of the right age, rocks that were formed in environments where They are rare, but we have them. There are some very good ones from North America. Actually, some of the best ones are from not too far from where I grew up, which is in central Illinois,

not too far from Chicago. And there's a little town called Wilmington, Illinois, a little town that is on Route 66 or the old Route 66, of course, which doesn't exist anymore. But it's a coal mining town. And that's the town that my mother grew up in. And little did she know that she was actually growing up on one of the great fossil sites of the world, because there's a lot of coal seams there. That's why my ancestors came over from Italy

to the US to mine that coal back in the late 1800s. But in those coal seams, in between those coal seams, there's these little ironstone rocks. They're about the size of your fist, most of them. They look like a rusty potato is the best way to explain them. And you can crack them open and you can get beautiful fossils inside, including fossils of some of these early synapsids and some of their close relatives. And then there's other ones that are from other places in North America and Europe and elsewhere. There's some great ones from Nova Scotia in Canada. These fossils show that these synapses were starting to diversify in that coal swamp world about 325 million years ago.

But they were small at that time. They were not top predators. You would never predict that these things eventually would go on and spawn, you know, saber-toothed tigers and mammoths and lions and whatnot. They were just getting their start at that time. We can see their beautiful fossils. That's the start of the fossil record of the evolutionary history of mammals. The Permian period. Now, this feels like the next step in the rungs of the ladder, as it were, in the story of mammals and their ancestors. Are we stepping forward in time here and we see some more evolution in these creatures? Absolutely. So the Carboniferous

period, the coal swamp world of those jungles and those really tall trees, hot, humid, that sort of world, that world ended. There was a collapse of those jungle forests. And the Carboniferous period turned into the Permian period. And a lot of this had to do with global climate change. There was an ice age going on around that time. Of course, as of the Carboniferous ushered in this new world of the next interval of geological time, which is called the Permian period. And by and large, this was a much hotter, drier time. And this was a time when all the lands started to come together into Pangea, the supercontinent. And there were vast deserts across much of that supercontinent. So animals that could live inland, that didn't need a lot of water, that could lay eggs far from the water, that could survive these harsher climates and these drier environments, they were poised to thrive in that world. And

the synapsids were very good at that. And so the Permian is when these synapsids went from bit players to superstars. They became the most dominant, preeminent, spectacular animals, the biggest animals on land, the biggest meat eaters, the biggest plant eaters. In fact, they basically invented plant eating. You didn't have big animals eating a lot of plants until these synapsids started to do it in the Permian. And of course, some of them were very fierce meat eaters preying on those plant eaters. And of course, some of them were very fierce meat eaters preying on those plant eaters. And this is the time when you got things like Dimetrodon,

which is a very, very famous animal with a big sal on its back, weighed a few hundred kilos, big head, sharp teeth like steak knives, top predator of its time. It's often mistaken for a dinosaur. You see it a lot in dinosaur toy sets there with T. rex and Brontosaurus. You see it a lot in books about dinosaurs, which read these books to my two

year old. I can't do it. It makes me so upset because Dimetrodon was not a dinosaur. It lived long before the dinosaurs. It was a synapsid. It was on our evolutionary lineage. Dimetrodon was more closely related to us than it was to a T. rex or a Triceratops. That just goes to show, in the Permian, these synapsids were glorious. They were doing so much. They were at the top of the food chain. They were very dominant. It looked like they would stay that way forever. There were so many different species.

As the Permian period went on, even bigger and bigger meat eaters evolved. There were these things called gorgonopsians or gorgons. It's a great nickname. It's like, you know, imagine out of a fantasy novel or historical saga, a gorgon. But these things had saber teeth, just like the later saber tooth tigers would evolve. These were bloodthirsty monsters. And then you had even bigger plant eaters. You had things that started, you know, weighing close to a ton. I mean, these synapsids, the Permian world was theirs. But then the Permian suddenly and unexpectedly ended with the biggest extinction ever. And that completely reshuffled the deck. And that caused the mammal lineage. I mean, there were no mammals yet, but the synapsids,

the precursors of mammals, it was a big setback. They were on top and then they were knocked down and it would take them a long time to recover. The Permian extinction, this huge cataclysmic, terrible event, you know. So how do mammals and what sorts of mammals are able to endure, I guess, to survive this huge catastrophe and enter the next period, that is the Triassic. What happened at the end of the Permian was the biggest disaster in Earth history. It was the closest life has ever come to dying out ever since the first living things evolved over three billion years ago. What it was was a mass extinction. It was one of those times when lots of species die off very suddenly all around the world

because of some common cause. And this was the mother of all mass extinctions. And some estimates show that maybe 95% of all species died out. So just imagine a world where 95 out of every 100 things dies, you know, just complete devastation, but maybe not quite complete devastation because a few things did survive. And from those survivors, a new world was born. And just imagine that you were one of those survivors just kind of getting through that. And on the other side, there's a vacuum. I mean, the opportunities would be endless. All of these animals, including those giant saber tooth meatothed meat-eating synapses and the

enormous plant-eating synapses, those things were pretty much all gone. The survivors had a new world. Many different groups of animals prospered in that new world. The Permian ended. Then the next interval of time after the extinction was the Triassic period. As we talked about in our last interview with dinosaurs, this is when dinosaurs got their start in the Triassic period. And as we talked about in our last interview with dinosaurs, this is when dinosaurs got their start in the Triassic. They were part of that recovery from this horrible extinction.

This is when the first turtles evolved. This is when the first crocodiles evolved, the first pterodactyls. So many of the most familiar groups of animals got their start in that brave new world after the end Permian extinction, as did mammals, because among the survivors were some synapsids that were smaller. They were able to burrow, so they were able to hide really easily. They were able to grow and reproduce really quickly. They were able to reproduce within a year of being born. You know,

this is a major thing. These were called cynodonts. They're a group of synapses called cynodonts. And these cynodonts, and we have great fossils of them, by the way, from South Africa. Many of them are fossilized in their burrows, which is just incredible, exquisite preservation. And it shows us that they did burrow, that they could hide, that they could hunker down and get through the worst of this chaos. But from those cynodonts that survived, the first mammals emerged in the Triassic, the first true mammals. We could now get to a point where we can call things mammals. Of course, it's all based on definitions, but there are certain things that mammals have that no other animals have. Things like hair, feeding your babies through

mammary glands. That's a really unusual thing. Differentiated teeth. You know, you think of a dinosaur, you think of a T-Rex, all those teeth look the same. But a mammal? No. I mean, look in our mouths. We have incisors at the front of our mouths that can grab food. We have canines behind that can slice food. We have premolars and molars that can crush food. You know, that's a mammalian thing. Mammals have big brains compared to most other animals. They have really keen senses of smell and hearing in particular. All these are the things that make mammals mammals.

The things that define mammals. The things that make us a mammal, a tiger a mammal, a dog a mammal, but not a dinosaur a mammal. And these are all things that were evolving in these cynodonts that survived that end Permian extinction as they were adapting to this empty world, but competing with the new dinosaurs and crocodiles and turtles and pterodactyls and so on. First of all, Cynodonts, I know that we're both Walking With Dinosaurs fans. And, you know, one of the stars of that first episode were the Cynodonts of the Triassic. They're such incredible creatures. But what is it about their adapting during the Triassic

which leads them to evolve these mammal qualities, shall we say? What causes this? When we look back at evolution, I mean, you know, we have to remember evolution doesn't plan ahead. Evolution doesn't look into some distant future and put together some grand plan. There was no moment in time in the Carboniferous or the Permian where, you know, natural selection decided, hey, we're going to make some small, furry, warm-blooded, big-brained creature that feeds its baby's milk, you know, one day. I mean, evolution only works in the moment through natural selection to adapt organisms to their particular environment. And often that means when there is some kind of

stress, there is some kind of threat, there's something that can affect animals. It's those that are better adapted, that have traits that can better endure that, that are better able to survive, better able to reproduce. And then those traits filter through the population. And that's how natural selection works. When it comes to mammals, you know, turning a synapsid and then, you know, a cynodont into a proper mammal, again, you know, a small furry animal with high intelligence, warm-blooded metabolism, fast growth, all these things that make mammals mammals. I think there were probably two major components to that. First of all, was that extinction. That extinction was a great leveling event. I mean, it killed off almost everything.

And to survive that extinction, and then to prosper afterwards, you needed to be well-adapted. So a lot of mammal features seem to have evolved as part of that process of adapting to this very devastated and chaotic environment. The second thing is, because there were so many new groups of animals that were evolving in the Triassic period, there probably was a bit of an arms race going on. So some of these features, mammals probably evolved in order to survive in that world. And when it comes down to it, there really was this interplay of mammals and dinosaurs. Mammals and dinosaurs both originated around the same time. We're used to thinking of mammals as coming after the dinosaurs. You know, dinosaurs had their day, then mammals replaced them. I'm sure we'll get to this shortly. And, you know,

that is generally true. But it's not that mammals evolved only after the dinosaurs were gone. It's that mammals became dominant only after the dinosaurs were gone.a, but they went their separate ways, and dinosaurs were destined for grandeur. Dinosaurs became larger than Boeing 737 airplanes, you know. Mammals stayed in the shadows. Mammals and dinosaurs lived with each other for over 150 million years. They coexisted for an enormous length of time. And during that entire time, there was never a mammal, as far as we know, that was bigger than a badger. So dinosaurs kept mammals small. But conversely, mammals kept dinosaurs big. And by that, I mean mammals were so good

and became so good at living in those small-bodied, hidden, understory, undergrowth, anonymous niches that they kept dinosaurs out of them. You never saw a T-Rex the size of a mouse. You never saw a Triceratops the size of a rat. Dinosaurs couldn't get that small because mammals were holding those niches. Well, my friend, we're definitely going to get into, as you say, the reign of mammals post the dinosaurs. But i just really find this coexistence between mammals and dinosaurs really really interesting and to tell that story because it is extraordinary and we've talked about you know the rise of these first real mammals in the late triassic but of course from our last chat we

mentioned how at the end of the triassic there is this huge another extinction event which paves the way for the real rise of the dinosaurs but i'm guessing some mammals managed to survive this too and they continue to coexist during the jurassic that's right we're talking about hundreds of millions of years these long stretches of time there are these extinction events that punctuate these long stretches of time and these are the things that really divide the different empires of prehistory. The same way as we talked about with dinosaurs last time, that intervals of human history are often defined by great wars or famines or the death of a certain monarch or something like that. So we can draw these mass extinctions as these pivotal moments that divide up geological time.

And at the end of the Triassic period, about 200 million years ago, there was another extinction. So the one at the end of the Permian, that big one that was about 250 million years ago, then you had this 50 million year stretch where the first mammals and dinosaurs and crocodiles and turtles and pterodactyls,

they were all evolving, living together on that super continent of Pangea, competing with each other, interacting with each other. Mammals stayed small. The dinosaurs were not super huge yet because the crocodiles were still keeping them in check, as we talked about last time. But, you know, some of the dinosaurs were, you know, getting up to horse size, giraffe size. And then 200 million years ago, another extinction happens. And what happened then was the supercontinent began to

break apart. Obviously, it did. We don't have a supercontinent anymore. We have a North America and a Europe. We have a South America and an Africa. They're separated by the Atlantic Ocean. But before the water came in to fill those gaps in the cracking supercontinent, there were enormous volcanoes. The earth bled lava for 600,000 years. And these were not normal volcanoes. You know, this was not Mount St. Helens or Mount Etna or something like that. I mean, these were just cracks in the earth that opened up and just spewed out lava. And with the lava came carbon dioxide and methane, these toxic greenhouse gases. They warm the atmosphere. They led to runaway global

warming, and that led to another extinction. And this extinction is really what helped the dinosaurs, because it killed off a lot of the early competitors to dinosaurs, a lot of the crocodiles and giant salamanders and other things that were the top predators and top of the food chain animals in the Triassic. The extinction also seems to have helped the mammals, at least in the sense that they endured that extinction. And then when they got through to the other side, there were new niches to fill, new ways to prosper. But there were still dinosaurs, of course, and the dinosaurs were getting bigger and bigger. So mammals would still have to wait a long time to grow in size. But we're now after the Triassic, we're in the Jurassic

period. And during the Jurassic and the Cretaceous, these are the two real apogee times of dinosaur evolution. All the most famous dinosaurs are from this time. But there were plenty of mammals that were living underfoot of the dinosaurs during this time, and they continued to diversify. And although they were small, although again, none of them ever got bigger than a badger, there were some mammals that ate baby dinosaurs for breakfast. We have a fossil mammal from China that has the bones of a little dinosaur in its stomach. So boy, that really turns on its head, that classic trope of, you know, dinosaurs stomping on mammals. We also have other fossils of mammals, particularly from China, from the same

rock units that preserved the famous feathered dinosaurs. We had volcanoes burying these entire ecosystems, almost Pompeii style. We have a lot of mammal fossils from those same rock formations. And those mammals, they're all small, but they're very diverse. There's mammals that were runners, there's mammals that were scurriers, mammals that were climbers, mammals that could swim, mammals that had wings of skin that they used to glide. So all of this diversity was evolving while mammals were still pretty anonymous, while they were still supporting characters, B-list actors, whatever you want to call them, you know, in the shadows of the dinosaurs. But they were small, but they were experimenting. They were innovative. They were doing all sorts of things. And that innovation, I think, really helped them

take advantage later on down the line when the dinosaurs finally met their match. Absolutely. We will certainly not call this podcast B-list actors and actresses of the dinosaurs during this period. But as we are talking about the Jurassic and the Cretaceous, I think there's something I'd love to ask at this moment. Something we associate with animals is giving live birth. Mammals back then, during this period of the dinosaurs, did they give live birth? A lot of times we don't know for sure because it's not like we often find fossils of babies, fossils of eggs, but sometimes we do. There's a couple of things we do know. First of all, there are some mammals today that still lay eggs. Those are the monotremes, the duck-billed platypus and the echidnas. And those only live in Australia and New Guinea, you know, just one

corner of the world. They're really a remnant of a very archaic group of mammals that happen to hold on, barely hold on to reach the modern world. They still lay eggs. The fact that living mammals lay eggs and the fact that reptiles, you know, amphibians, all these other things, birds, you know, lay eggs as well, it means that probably most of these fossil mammals laid eggs. And it was only much later in mammal history that some mammals started to give live birth, and particularly live birth to well-developed young. Modern day marsupial mammals like kangaroos and koalas, they give live birth, but their babies are so minuscule, so feeble.

They're so premature that they have to develop further in the pouch. So it's really only placental mammals, the ones like us, that give live birth to much better developed young. And this is a major thing. And this came in really handy, I think, when the dinosaurs died, which mammals were able to take over. Well,

being able to give live birth like this is very important. And there's about 6,000 mammal species say a little bit more, but about 95% of those are placental mammals. So almost every mammal you know is a placental. Dogs, cats, horses, whales, bats, monkeys, humans, you know, we're all placentals. There's only these rare monotremes that lay eggs and marsupials that give live birth to little young that are an exception to that. Of course, you delve into the detail of all this in your book and the various species that emerge in the Jurassic and the Cretaceous. We're going to hop over that a bit now. We're going to go to the Cretaceous and to the extinction or just before the extinction because it seems like mammals in the cretaceous there's a lot of development i've got words here like

territorial revolution this seems to be quite big so much so that by the time just before the extinction event happens what's the situation of mammals? Where are mammals? How are they doing at the end of the Cretaceous period? Throughout the Jurassic and the Cretaceous, mammals were diversifying. They were not stagnant. I know I called them B-list characters, and they were in the sense that you wouldn't notice them really if you were there. They were not the superstars. They weren't the ones on the marquee. I mean, those were the dinosaurs the size of airplanes and the T-Rexes the size of London buses and stuff, you know. But the mammals were doing very well diversifying in

the shadows, and they were really variable. Again, there were climbers and swimmers and diggers and all kinds of mammals. As the Cretaceous went on, mammals became even more diverse because something really important happened in the Cretaceous. There was a new thing that evolved. And that new thing, it wasn't even another type of animal. It was a new type of plant. And these were the flowering plants, the most familiar plants to us today. The vast majority of plants that live today are flowering plants. And what you might not realize is that flowering plants are actually a really new evolutionary invention. The oldest fossils are only from the early Cretaceous period. A brontosaurus, a stegosaurus would have never seen a flower, would have never eaten a fruit.

But then in the Cretaceous, these flowering plants evolved. And that led to this evolutionary cascade. And that's what's called the Cretaceous Terrestrial Revolution. And really, it was a revolution. It was because flowers evolved. This was a new source of food, flowers and fruits. Not only that, there were all these new types of insects that co-evolved, you know, pollinating the flowers. So it led to this evolutionary explosion. And so for mammals and dinosaurs and everything else that was alive at the time, they now had a lot of new things they could eat. And this was especially true of these small mammals,

because things like flowers and fruits and insects, this is perfect food for animals that are the size of mice, the size of rats that are trying to eke out a living in a world that's still dominated by these enormous thunder lizards. So that led to a huge proliferation in the number of mammal species. And a lot of these are what we call multi-tuberculate mammals. Their time in the Cretaceous, you know, they were the mammals. They were the major group. There were so many species of these things. They lived all over the world. They kind of looked like rodents. They were not rodents. They were a more archaic group, but they had big buck teeth incis world. They kind of looked like rodents. They were not rodents. They were a more archaic group, but they had big buck teeth incisors. They could gnaw on things. They had

teeth in their cheeks that were really good for chewing through lots of plants. So, you know, they would have behaved and really looked like a squirrel or a gerbil or a small beaver or something like that. But these multi-tuberculate mammals were so supremely suited to this Cretaceous world of fruits and flowers and insects. And they were doing very well alongside things like T. rex and Triceratops, which were at the top of the food chain. They were the kings and queens of the underworld, of the underground. That's right. They were. I think I use an expression kind of like that. I've got it. Absolutely. I've got it quoted from your book right here and they were you know

if you were around back in the cretaceous you probably wouldn't have seen a lot of them kind of like rats today you know you know they're there you know there's a lot of them there you know they're going to come out at night you know know, but you might not have seen them, but you would have sensed them. They were a very important part of that world, even if they were not these big, brash, in-your-face, obvious giants like the dinosaurs. Throughout June on Not Just the Tudors, we're honoring Queen Elizabeth II's platinum jubilee by focusing on queenship in the 16th and 17th centuries. I'm Professor Suzanne Lipscomb, and all this month with my guests, I'll be exploring the coronations of Tudor queens, Queen's regnant and Queen's consort, who wielded power in ways we haven't thought about.

Really, when we begin to look at queen consorts, we notice that there's a lot of ways that the Renaissance court that women could hold informal power through their relationship with the king. Then there's the queen who ruled over the Spanish Netherlands and the female Swedish king. You heard that right.

What did a 17th century person actually mean by saying, oh, she dresses like a man? If she would have worn male clothing, she wouldn't have been able to rule Sweden. So for a month of all things magisterial and monarchical, look no further than not just the Tudors from History Hit. hit. If we get to the end of the dinosaur period, because around 65 million years ago, Steve, what happens?

This was the single worst day in Earth history. That extinction at the end of the Permian was the worst time to be alive, generally, because 95% of stuff died out. But that was over a more prolonged period of time. At the end of the Cretaceous, literally one day, this asteroid fell from the sky. It was about six miles, about 10 kilometers wide. So it was a rock the size of Mount Everest, or a rock as wide as the entire city of Edinburgh, where I live. And it was traveling through the cosmos, traveling faster than a speeding bullet, literally it was. And it could have gone anywhere. I mean, it was just random trajectory. You know, it could have gone anywhere,

it could have sailed right on by the Earth. But it happened to make a beeline and it smashed right into what is now the Yucatan Peninsula of Mexico. So close to the tourist town of Cancun, you can see part of the crater. When this asteroid hit, it punched a hole in the earth more than 100 miles wide, more than 20 miles deep. It impacted with the force of over 1 billion nuclear bombs put together. And it just caused untold destruction. Within moments, this cascade was triggered. And you had wildfires and tsunamis and earthquakes and hurricane force winds. And of course, these things were worse the closer you were to the impact, but they had global repercussions. And then things became really bad when the fallout from that asteroid impact

rained down on the whole world. All this hot rock and dust, it heated the atmosphere like an oven and it caused spontaneous wildfires to burn. And then all the soot from those fires and all the residual grime from the collision went into the atmosphere and it blocked out the sun for years. This was a nuclear winter. The earth went cold and dark for years. And so plants could not photosynthesize. They died. The only reason that their species persisted is because seeds can survive for a while in the soil.

Thank God for that or the plants would have been dead. But the actual forest collapsed. The plants couldn't make their own food. With no food to eat, the plant-eating species died. Then the meat-eating species died. These ecosystems collapsed like houses of cards. And this was the end of the age of dinosaurs. Dinosaurs had dominated the world so thoroughly for well over 100 million years. And literally in one day, their empire toppled. Many other things died too, including

a lot of mammals. This was not a good time to be alive for anything. And some estimates from fossils suggest that more than nine out of every 10 mammals, more than 90% died in that extinction. So mammals almost went the way of the dinosaurs. Our ancestors barely squeaked through, but they did. We did have ancestors that faced down the asteroid and survived it and got through it. Otherwise, we wouldn't be here. But in the grand scheme of things, I mean, the odds were not on our side. But some mammals got through. What we see from fossils is the mammals that survived tended to be the ones that were smaller. So they could probably hide easier. They could burrow easier. they could scamper away from the danger easier, they could grow faster. And then they were the ones that had more omnivorous diets. They could eat a wide variety of foods, which certainly came

in handy when the Earth just turned into an apocalyptic anarchy when that asteroid hit. So mammals survived, but only just from what you're saying there this cataclysmic event but this can we say just like at the end of the triassic and the age of the dawn of the dinosaurs does this also pave the way therefore with the end of the dinosaurs for the real ultimate rise the age of the mammals it did finally mammals had another chance if you think all the way back to that end Permian extinction, 250 million years ago, before that extinction, there were those synapsids at the top of the food chain. They were not mammals, but they were the ancestors of

mammals, the things like those saber-toothed gorgons and these giant plant eaters. They were at the top of their game, really, and then that extinction knocked them back. The synapsids made it through with the cynodonts and then the first mammals and so on, but they were small. You know, they ceded the large sizes to the dinosaurs. The dinosaurs seized those niches. Now, finally, the mammals could move back in. It was a long waiting game, but they could because T. rex, Triceratops, you know, all these dinosaurs, they died. It seems like they were too big. They grew too slowly. They had too specialized of diets to make it through that sudden chaos. They were not holding a good hand of cards in an evolutionary sense. But those surviving mammals were, although again,

most mammals did die, but those few mammals that made it through now all of a sudden, Although, again, most mammals did die, but those few mammals that made it through, now all of a sudden, there's no T. rex anymore. There's no Triceratops anymore. There's no long-necked dinosaurs anymore. So how did mammals respond to that? Well, they responded by diversifying, and diversifying very quickly. And particularly, they got big. And remember that during the 150 million years they lived with the dinosaurs, no mammal ever got bigger than a badger. Within a few hundred thousand years of the asteroid impact

and the death of the dinosaurs, there were mammals the size of pigs. And within a million years, there were mammals that were roughly the size of cows. And so that's incredible. So mammals had an opportunity. They seized it. They grew in size. They diversified. They started to eat a lot of new foods. They started to move in a lot of different new ways as well. And many of the familiar groups of mammals that we know today didn't necessarily originate at that time. It's not like we see monkeys and horses and whales right away.

But their ancestors did. And these were these first placental mammals, the ones I alluded to that give live birth to well-developed young. And being able to do that really gave them a head start in life. Being able to give birth to a baby that already has been nourished in utero, inside its mother's womb for so long, protected, nurtured, and then being born at a pretty developed stage where a lot of placental mammals, humans are different because we're quite peculiar, but a lot of placental mammals think horses or cows, when their babies are born,

they're walking right away. They're going out eating plants before too long. So that was probably part of the key survival in addition to some of the other things we've talked about, mammals being able to eat lots of food and hide better and so on. As we've mentioned in the past, you know, how post-Triassic the dinosaurs, all this diversity, diversification, but they also spread to all corners of the globe alongside this rich amount of diversification of the mammals post the dinosaur extinction. But do they also spread to all corners of the mammals post the dinosaur extinction. But do they also spread to all corners of the world at that time?

Yes, they did. So I'll back up slightly. So in the Cretaceous, living with T. rex and with Triceratops, there were all these multi-tuberculate mammals, these ones that were the kings and queens of the underworld, the ones that looked like rodents that were eating flowers and fruits and insects. But there were also early members of the marsupial and placental lines. They weren't the modern types, but they were ancestors. They were there. And in fact, there were quite a lot of these early marsupial animals, especially living in North America and in Europe and in Asia. The extinction almost completely wiped them out.

The marsupial group almost was eliminated. The extinction almost completely wiped them out. The marsupial group almost was eliminated. And it wasn't too long after that they were just extinguished on the northern continents. And they won a reprieve by going south and migrating to South America and then eventually to Australia. So you have a lot of marsupials in South America and especially in Australia today. But South America was an island continent, and Australia still is, for basically the entire time, starting with the time of dinosaurs, continuing only to about two and a half million years ago. So these marsupials, some managed to get there and they formed their

own kingdom there. The monotremes that we talked about earlier, the ones that lay eggs, there's only a handful of species of those that have miraculously survived, and they only lived in Australia and New Guinea and that part of the world. The other mammals, the placentals, these are the ones I really want to focus on. They, after the extinction, they really prospered. They were the ones that really started to proliferate after the extinction. We're now in an interval of time called the Paleocene period. And the Paleocene was the time that placentals started to really assert themselves. And they spread widely around the world, at least in the northern continents, because again, South America, Australia, even Africa, they were all island continents at that time. So they started to give rise to their own peculiar mammal groups, including their own peculiar placental mammal

groups. So you had some placentals that managed to get to South America and Africa, probably by hopping across islands, that kind of thing. Elephants and manatees and those kind of things have their heritage in Africa. Sloths and armadillos, they have their heritage in South America. But so many of the other placental groups, they spread widely around the northern continents. And they would spread even more widely after the Paleocene in the Eocene period, which came next. Talk to us through this Eocene. This is definitely going out of my comfort zone. It ends with dinosaurs in my comfort zone. So explain this to us. That was what it was like for me when I started my career as a paleontologist. And I've had such a blast just moving on and learning so much more about mammals. And a lot of my research is about mammals. I'm not just

writing this book about mammals. I mean, a lot of my research has turned towards mammals. What I'm most fascinated in is those Paleocene mammals, those first placentals that took over from the dinosaurs that balloon their bodies, that filled all these new niches that really established the world we know today. But a lot of these Paleocene placentals, they were weird. That's the best way of putting it. You know, it's not like there were bats and horses and whales and monkeys that were living right after the dinosaurs. There was this transitional period where you had these archaic placentals, and there was a great diversity of these things. Some of them were the ancestors of today's placentals. Others were their own dead-end experiments that didn't leave any

modern descendants. But these animals generally were pretty strange. They were really stocky. They had these bones that were really robust, and they had huge muscles on their skeletons. A lot of them were diggers. Some of them had hooves, pantodons, condylards, taniodons. These are mammals you don't know. These things are extinct. But at their time in the Paleocene, they were the ones that were innovating, that were evolving. And from these extinct animals, or at least some of them, today's placentals emerge. And that really happened in the Eocene. That's when we start to see recognizable placental mammals. That's when we start to see the first obvious horses and cattle and primates and so on. That's when we see the first bats and the first

whales. And what happened is those animals were evolving from these archaic Paleocene, first pioneering placentals. And there was a big warming spike, a huge spurt of global warming as the Paleocene ended and turned into the Eocene. This was about 56 million years ago. And this is the hottest the Earth has been. You know, it has not been hotter since then. This was an extreme global warming spike. It's probably the single most important episode of global warming in the geological record for us to study, to compare what's happening today to the past, because this was a very sudden spurt of warming. Of course, not caused by humans burning hydrocarbons, but it was caused by volcanoes. All this magma was percolating up through the earth, baking the crust as it did so.

As it burned, it released all this carbon dioxide and methane. That volcano is called Iceland. That volcano is still operating, just at a trickle compared to what it was back then. As the Paleocene turned to the Eocene, there was a rupture at the far north, in the Arctic, basically. Before then, North America, Greenland, Europe were still connected, but then they ruptured. And then you had all this lava come up. The remnant of that is Iceland today, and the volcano is still active, you know, but it's just more annoying than anything today. You know, it erupts, it shuts down flights for a few weeks, you know, very annoying, but not catastrophic. At the end of the Paleocene, it was catastrophic. There was so much lava, it led to this global warming spike that took place over a few tens of thousands of years.

Now, strangely enough, that did not cause a huge extinction, unlike some of the extinctions we've talked about in the past, where global warming did cause a big extinction. Instead, what this episode of global warming did was it caused migration. It opened up these new travel corridors in the high latitudes. The high latitudes were accessible now. There were crocodiles basking in the Arctic during this time. There were palm trees above the Arctic Circle. Mammals could spread widely. So this unleashed an age of mass migration. And out of this came these more recognizable placentals. And this is when we see the first primates, the first horses, the first cattle materialize all across the northern continent. It's like a swarm of locusts. They're

everywhere. And this is when we can really start to see our world start to emerge. Not only are there a lot of mammals, but these are mammals we can recognize. You can look at them and say, this thing is a horse. This thing is a bat. This thing is a primate. Now, you did mention right at the start, the Ice Age. Many of us no doubt would have watched Ice Age when we were younger or the series or prehistoric park, maybe the wo mammoths the saber-toothed tigers maybe even the giant sloths and the like i mean how do we get from this period which you mentioned the eocene to this time of this ice age and some of the most iconic now extinct mammals of several tens of thousands of years ago so 56 million years ago paleocene turns to the eocene the big global

warming spurt, the horses and cattle and primates spread around the northern continents, as did other groups like bats and whales and so on. This was a manic time in evolution. And really, by the end of the Eocene, you had a very recognizable set of mammals. And then as the Eocene ended, the world really started to get cooler, a switch from essentially a hothouse world to a world that was getting colder and colder and colder. And this had to do with the movements of the continents largely. So Antarctica became isolated over the South Pole. That led to a new circumpolar current, which was basically a global air conditioning system. And there were

other aspects of it as well. India smashed into Asia, the Himalayas rose up, it caused all this new erosion, all this new rainfall. So there were big changes in the climate. But the most important fact is the world switched from a world that was really hot to a world that was getting colder and colder and colder. And over time, that would culminate in the Ice Age. Along the way, flowering plants proliferated

and the new type of flowering plant that we call grasses, grasses have flowers, those plants, they became very common in open spaces, and they started to form grasslands as the world got cooler and cooler. So it became less of a jungle sort of world, more of a grassland world as the temperatures got colder. Of course, it's a little bit more complex than that, but in general, that's what we see. The spread of grasslands across much of the continental interiors as the world got colder. And then, a few million years ago, the world got really cold, and that's when the ice ages began. And I say ice ages, really, because, I mean, it is an ice age, but there have been pulses. There have been dozens of these pulses. Times when it gets

really cold and the glaciers grow, times when it warmed up and the glaciers melted back. And the glaciers, by the way, this is mostly a northern hemisphere thing. And what I mean by these glaciers, this was the polar ice cap. It's the polar ice cap that would extend down south and then retreat and extend and retreat. And this would go back and forth. And the most recent extension was not that long ago. It was only about 10,000 years ago that that ice cap retreated. A little over 10,000 years ago, there would have been a mile of ice covering Edinburgh, covering Stockholm, Dublin, covering Chicago, New York, Montreal. Steve, it's the original beast from the east, isn't it?

Absolutely. Absolutely. Or that is what the world was like. And then south of those ice sheets of those glaciers, this is where mammoths and saber tooth tigers and the megafauna roamed. And these were spectacular mammals. They were huge mammals. They were bigger than any mammals that live on land today. And they were here so recently. They only went extinct, most of these animals, about 10,000 years ago. So a little more than 10,000 years ago, in Europe, in North America, in Asia, you would have had hairy elephants. You would have had these sociopathic tigers with their enormous foot-long saber canines.

Deer with antlers the size of tables, you know, the most flamboyant mammals that have ever lived. Beavers the size of small cars. Down south of the equator, you had armadillos the size of Volkswagens. You had sloths that lived on the ground and were 10 feet tall. In Australia, you had wombats that weighed over a ton. And I could go on and on and on. The megafauna was spectacular. These things were at least as incredible as dinosaurs. And they're mammals, like us. And they lived up until about 10,000 years ago, which is nothing. That's just a hiccup of Earth history. And sadly, it probably was largely our actions that led to their extinction. Maybe not entirely. Climates, of course, were changing very dramatically then too. But I think it's

no coincidence that continent after continent, we see that when humans arrived, the megafauna didn't have much time left. Well, Steve, that's a nice way to wrap it all up. This has been absolutely great chat. Your mission of this episode was to convince us all that mammals, the story of the rise of mammals and their reign is just as extraordinary as the dinosaurs. And I for one think you've definitely achieved that. Last but certainly not least, your new book all about this topic, it is called The Rise and Reign of the Mammals. 325 million years of evolution from those coal swamps through the age of dinosaurs and mammals lived in the shadows to mammals surviving the asteroid, thriving afterwards, getting through these global warming spikes, turning into monkeys and whales

and bats and everything we know today, then enduring the ice ages, the megafauna, all the way up to us. There is a chapter at the end all about humans that fits into the rest of the narrative. But if you do want to know about how humans evolved, there were times when there were dozens of species of fossil humans of other species. This is a very unusual time to have only one human species. So all this is to talk about in the book. For those of you that have read The Rise and Fall of the Dinosaurs, my book from a few years ago. This is in some ways a follow-up to that book. It's written in a similar style. I would say there's about 10-15% more hard science, a little bit less of the stories of me traveling around drinking beer with colleagues. There are some of those stories, but because I haven't studied mammals quite as long as dinosaurs,

there's a little bit less of that personal kind of biographical touch. A lot more though about other scientists, about my colleagues, my students, my mentors, the people that have inspired me and all the incredible discoveries that they've made. So the book is out. So I hope that people enjoy it. I hope it's a worthy follow-up to my dinosaur book. And I hope actually that it eclipses that book because this is us, is our story and that to me is what's so fun about it this episode we've only just scratched the surface of the whole topic and it only goes to me to say thank you so much for taking the time to come back on the podcast today absolutely my pleasure Tristan and thanks for having me again I look forward to the next time there was professor Steve Brissati talking us through the rise of the mammals i hope you

enjoyed that episode steve is such a brilliant contributor a brilliant guest and don't you worry we're aiming to get steve back on the podcast in due course because it's also such an amazing area of prehistory now last couple of things from me this This week I've been at Chalk Valley. It might be a bit late now because we are releasing this episode on Thursday but I am still at Chalk Valley tomorrow on the Friday this week talking to Professor Rebecca Ragsykes all about Neanderthals that afternoon. If you can make it I know it's last minute but if you can I'd love to see you there and it promises to be a really really fun chat I am really looking forward to talking all things Neanderthals but apart from that otherwise if you want more ancients content you know what you can do you can subscribe to our weekly newsletter via a link in the description

below every week I write a bit of a blurb for that newsletter telling what's been happening in team ancient history hit world that week and of course last but certainly not least if you'd be kind enough to leave us a lovely rating on either apple podcasts spotify or wherever you get your podcast from i would greatly appreciate it the team would love it and of course it helps us spread the ancient history word let us get these stories out to more and more people and really show why ancient history is the best and we all know that but we just need to get it out more and more and more. That's enough rambling on, and I'll see you in the next episode.