Edinburgh University paleontologist Steve Brusatte talks about his May 2018 Scientific American article, "The Unlikely Triumph of the Dinosaurs," and his new book, The Rise and Fall of the Dinosaurs: A New History of a Lost World.

Steve Mirsky:    Welcome to Scientific American Science Talk, posted on May 23, 2018. I'm Steve Mirsky. On this episode:

Steve Brusatte: Dinosaurs are cool. Dinosaurs are amazing. But they're more than just movie monsters or a childhood obsession. These were animals that ruled the world for 150 million years. They had to deal with drifting continents and volcanoes and asteroids and rising and falling sea levels, changes in temperatures.

Mirsky:               That's Steve Brusatte. He's a paleontologist at the University of Edinburgh. Although, as you can tell from his accent, he's American, educated at the University of Chicago, Columbia University, and the American Museum of Natural History. He wrote the cover story on dinosaurs in the May issue of Scientific American. Plus, his book, The Rise and Fall of the Dinosaurs was published just last month. We spoke by phone.

                           “The Unlikely Triumph of Dinosaurs," your article in the May issue of Scientific American. You talk about the fact that for a long time, it seems like among the public and in the scientific community, it was kind of an assumption that dinosaurs were an instant success, instant in terms of geological time scales, evolutionary time scales. But, according to the article and some of what's in your book, The Rise and Fall of the Dinosaurs: A New History of a Lost World, it's not necessarily the case. It took them a while to get started.

Brusatte:            That's right. That's right. If you go to a museum and you stand underneath the skeleton of a T. rex or if you watch one of these dinosaur documentaries on television and you see the CGI Brontosaurus thundering around, these are majestic animals. These are awesome animals. These are fierce, huge, dominant creatures. For a long time, there was a real mystery about how dinosaurs rose up to become animals like that.

                           The thinking was that it happened quite suddenly, that dinosaurs were superior, that there was something about them. That once they originated, they had such an advanced biology and advanced type of body that they spread all around the world, that they spread around almost like an infectious virus, that they outcompeted the other animals of the day way back in the Triassic period, the days of the supercontinent, Pangea. But we now know that's not the case. There have been so many new fossil discoveries over the last decade or so, fossils of the very first dinosaurs, the animals living with the first dinosaurs.

                           It turns out that the very first dinosaurs were quite small. They were humble animals. The very closest relatives of dinosaurs, these things called dinosauromorph, the immediate ancestors of the dinosaurs; they were just the size of a house cat. They were these awkward, gangly-looking animals that were sprinting around on four stilty legs. These were the animals that dinosaurs came from. There weren't that many of them. They were living in the shadows. But they were the stock that gave rise to the dinosaurs. It took a good 50 million years or so for those animals to diversify, to grow in size to become the dinosaurs that we all know and love.

Mirsky:               So, 50 million years is what it really took, it looks like. What was the thinking that it only took a million or two years for the big dinosaur explosion to have happened?

Brusatte:            Yeah. So, what we see now with the fossils that we have is that a lot of these old ideas, they were just a little bit simplistic. There wasn't a whole lot of fossil evidence in the past. Now, the new fossils, they do give us this picture of dinosaurs gradually rising up. During much of the Triassic, they were living alongside their close cousins, the crocodile-type reptiles. These were early crocodiles and their close relatives. They were very different from the crocodiles of today. We're used to alligators and crocodiles, these animals that they're all kind of the same. The scaly, green creatures sprawling around, living at that interface between water and land.

                           But today's crocodiles are just a shell of their former selves. Back in the Triassic, crocodiles and their cousins were hugely diverse. There were crocs the size of buses. There were top predator crocs. There were crocs that ate plants. There were crocs that were covered in armor. There were crocs that looked like little greyhounds that sprinted around.

                           These crocs, they were the top animals. They were at the top of the food chain. They were the ones that were the most dominant. The dinosaurs really were living in their world. That was true for a long time until, right at the end of the Triassic period, about 200 million years ago, the supercontinent, Pangea, it started to break apart.

                           As a continent breaks apart, lava comes up and fills those gaps between the little bits of crust that are moving away from each other. That's what happened. This wasn't just a little bit of lava. This was a time of super volcanoes. You had pulses of these huge volcanoes erupting for at least 600,000 years or so. For some reason, the crocodiles and their relatives couldn't handle it.

                           We know the Earth got really hot. We know there was runaway global running from all the carbon dioxide and the methane and all the other noxious, nastiness that spewed out of those volcanoes with the lava. So, there was a runaway greenhouse event. Most of the crocs died. The only ones that survived were the few species, the few lineages that eventually led to today's crocs.

                           Whereas, the dinosaurs, on the other hand, just sailed right on through. They just kept on trucking. We don't really know why. We don't have a good answer as to why. I think that's one of the biggest remaining mysteries about dinosaurs; why the crocs were hit so hard? Why the dinosaur pretty much went through that extinction unscathed?

                           But regardless of the answer, after that extinction, we're now in the Jurassic period and you have a whole new world for these surviving dinosaurs to conquer and they conquered it with gusto. They spread around the planet. They grew to enormous sizes. Some of them started to get a bit smaller and grow out their arms and grow feathers and wings and become birds. So, now, finally, a good 50 million years after those first little, humble, cat-sized dinosauromorphs, we are finally in the age of dinosaurs.

Mirsky:               I mean imagine, we're all seeing footage of the volcano in Hawaii right now. That's puny compared to what you're talking about. Imagine that going on for a rift of thousands of miles and for 600,000 years?

Brusatte:            Yeah. It's something that's so far out of scale with any human experience that it's just hard to imagine what it would be like. The volcanoes that we're used to are the ones in Hawaii, the ones that are erupting now or Mt. St. Helen's or Pinatubo, some of these cone-shaped volcanoes that blow their top occasionally and send out a bunch of ash and sludge and that's that. But what we're talking about here were super-volcanoes, volcanoes that were erupting out of huge, probably Grand Canyon–sized fissures in the earth. Tsunamis of lava coming out of them for these long pulses of time. With the lava, all of those poisonous gases.

                           So, it would have been a scarred landscape, the likes of which we've never really seen before. That was a probably. This was one of the biggest mass extinctions ever in the history of the Earth. Someway, somehow, dinosaurs survived. That is really what triggered their proper rise to dominance.

Mirsky:               There's a little bit of irony in that we're always thought of – the mammalian line is always thought of as this group of really tiny, little, scurrying nothings that happened to get through the Yucatan Peninsula asteroid hit that wiped out the dinosaurs. It was that that enabled mammals the chance to grow and diversify and get big and all that kind of thing. I don't think it was thought of that the dinosaurs, themselves, were in that position before this previous mass extinction.

Brusatte:            That's right. There's some real kind of cosmic symmetry going on here. Dinosaurs, as we know, they had a spectacular fall. Very suddenly, they were wiped out by this six-mile-wide asteroid, 66 million years ago. The mammals then, some mammals, were the plucky survivors, these small, little, furry things that were scurrying around that could hide really easily, that were really adaptable, that could eat lots of different foods. They were the ones that made it through and then started the next empire of Earth history, the one that led to us, the empire of the mammals.

                           But the dinosaurs, too. They had their own similar origin story of having to survive a mass extinction of, first, starting out small, starting out humble, living in the shadows, having to be adaptable and then surviving an extinction. So, this happens with some regularity in the history of life. Empires rise and fall and sometimes they can fall quite suddenly.

                           Oftentimes, when empires fall, the new empires rise up from these very, very almost anonymous sources, these small, humble, little creatures that have been biding their time, living in the shadows, being really adaptable. They're the ones that often have a leg up when a global catastrophe hits. It's these kinds of things that make fossils and paleontology relevant. This is why we study dinosaurs.

                           Dinosaurs are cool. Dinosaurs are awesome. Dinosaurs are amazing. But they're more than just movie monsters or a childhood obsession. These were animals that ruled the world for 150 million years. They were at the top of nature before humans were.

                           They had to deal with drifting continents and volcanoes and asteroids and rising and falling sea levels and changes in temperature. They had to deal with global warming events. So, now, we as humans, wear that crown that once belonged to the dinosaurs. There's a lot, I think, that we can learn from the dinosaurs and, hopefully, we can learn enough that we don't share the same fate.

Mirsky:               Yeah, the dinosaurs didn't have a space program, which is probably important.

Brusatte:            [Laughs] As far as we know, dinosaurs never blasted off the moon or off to Mars. Maybe that'll be one of the things that can save us eventually if things get really bad. But who knows? It's one of these fun what-ifs, that if that asteroid never hit, maybe dinosaurs would have kept living. I'm sure they would've. They had been around for so long. They had been through so much before. Maybe they would have evolved in the direction of the way humans have gone.

                           There were some dinosaurs with big brains and keen senses, some of these small, little raptor dinosaurs living right at the end of the Cretaceous, right when that asteroid hit. If those animals had survived, if they had more time to continue to evolve and continue to adapt and get bigger brains, maybe they would have started to go down that primate route. This is when we can really let our imaginations run wild in a science fiction fantasy type of way.

                           That's one of the things about paleontology is that this is Earth history. This is the story of what's happened in the past. That can give us clues as to what happens in the future. But we can also start to think about, "Well, what would have happened if that asteroid didn't hit, if those volcanoes didn't erupt?" It's like asking, "What if the Arch Duke was never shot?" So, that can be a lot of fun.

                           This is a science where there's a lot of imagination. That, to me, is one of the great thrills of being a paleontologist is just reimagining these lost worlds based on small bits of evidence, scraps of bone and teeth and footprints. But then, also, the reverse. Starting to think, "Well, how is this relevant to our world and what might have happened if these animals never left us?"

Mirsky:               Yeah, when you go out into the field, you're really like CSI, but reconstructing a crime that happened 100 million years ago.

Brusatte:            Yeah. I like to draw the parallel a lot with detective work. For paleontologists, fossils are our clues. They are the clues as to what happened in the past. We have to look for fossils to reconstruct, to reimagine some ancient scene. Dinosaurs moving around, interacting with each other, hunting, growing up, reproducing. The same way, or at least a similar way that a detective would look at fingerprints and shell casings and other things and have to reconstruct a crime scene.

                           So, when we go out and look for fossils, we're maybe not as high-tech as most detectives or we're not usually as well-funded as a lot of police departments these days which says something about the rate of funding in science, but we use every tool at our disposal. When we're out in the field, it's usually a fairly primitive game. I have to say, it's a lot of walking around. It's a lot of looking for fossils poking out of the rock and then getting out hammers and chisels and saws and getting those rocks out, protecting them with plaster bandages.

                           But it's when we bring things back into the lab, when we bring these fossils back home, that's when we can really start to go all CSI, high-tech on things. So, we can use CAT scanners to look inside of these bones to see, for instance, the brain cavities of dinosaurs, the inner-ear cavities of dinosaurs and digitally reconstruct what the brains and the ears and the other sense organs would have been like. Or computer animation software where we can input laser-scanned images, models of dinosaurs and we can see what sort of motion they were capable of.

                           How fast could they move? Could they run? Could they stick their necks way high up? Could some of them fly? So, new technology has changed quite a bit and we now know so much more about dinosaurs because we can study them in detail with a lot of these really high-tech gadgets.

Mirsky:               Speaking of what you can discover by studying with the high-tech gadgets, in the book, you talk about the feathered dinosaurs of – you want to pronounce it for me – Liaoning?

Brusatte:            Liaoning. Yep, that's right. Good.

Mirsky:               In China. You say that they're the most significant dinosaur discovery of your lifetime.

Brusatte:            Yeah, absolutely. I think these things are, without doubt, the most important dinosaur discoveries of the last several decades and some of the most important of all time. These are the dinosaurs that tell us, definitively, no doubt about it, that birds evolved from dinosaurs. That's because these are dinosaur skeletons that are preserved in immaculate condition and they're surrounded by feathers. They have coats of feathers. Some of them even have wings. They have quill pen feathers on those wings so similar to the birds of today. The idea that birds evolved from dinosaurs was first proposed back during the time of Darwin, in the 1860s.

                           But there weren't that many fossils at that point. It took a long time for scientists to find more fossils of dinosaurs with features of the skeleton that were shared with birds, things like wishbones, for instance. But still, scientists were kind of looking for a trump card. So, that finally came in the late 1990s when these farmers in China stumbled upon these feathered dinosaur fossils. These were a one-in-a-trillion discovery.

                          It's so hard to preserve feathers. Feathers are soft tissues. They decay really quickly. They break down really easily. They don't normally turn to fossils in the same way that bones or teeth or shells do, the harder bits.

                           But these dinosaurs lived about 125 million years ago in this ancient wonderland, jungle environment. Big forests, lakes. A real nice place to live, except there were some cone-shaped hills in the background and these were volcanoes. They would periodically erupt and bury these dinosaurs in ashy sludges, kind of similar to Pompeii.

                           You'd get these dinosaurs preserved going about their everyday business and locking in the fine details of the feathers and other soft tissues. That sealed the deal. That finally said, even to the most ardent skeptics, "All right, we know that dinosaurs had feathers now. These things were the ancestors of birds."

Mirsky:               You talk about the fact that even the wings that first evolved were not for flight.

Brusatte:            That's right. That's a real stunning realization, I think, that wings didn't evolve for flight. We think of birds. We think of their wings. We think of their wings as the airfoils that power them through the air just like the wings of an airplane. Of course, they do. They do.

                           But wings do a lot of other things. This realization stems from the feathered dinosaurs of China. We now know that most dinosaurs probably had some type of feather. So, feathers evolved very early in dinosaur history. But they were simple. They looked like hair. These were strands, filaments. They probably evolved to keep dinosaurs warm, to help regulate body temperature, the same way that hair evolved in mammals.

                           Then, later on, some dinosaurs started to change those feathers. They got longer and they started to branch out and they started to get flatter. They turned into the quill pen feathers we know so well that started to line the arm and make wings. But the very first wings show up in dinosaurs that are far too big to fly, things like the ostrich-mimic dinosaurs, ornithomimosaurs like Gallimimus from Jurassic Park, those type of animals. They had wings. We know that from real fossils. But they are far too big to fly and their arms are far too small to have big enough wings on them to hold up the body in the air.

                           So, that leads to this conclusion that wings must have evolved for something else. That maybe isn't too shocking when you think about it because wings do a lot of other things today in birds. Birds use wings for display. They use wings to protect their eggs and lots of other functions as well. So, we think – we don't know for sure – but we think display may have been why the first wings evolved, because these dinosaurs wanted to intimidate rivals or attract mates. We know that modern birds use their wings for display really regularly and their feathers as well. Think of a tail of a peacock. That's purely there for display.

                           But also, now, scientists have found out a way to tell the colors of dinosaurs by looking at the feathers under really high-powered microscopes and identifying these melanosomes, these pigment vessels. They can tell what color the dinosaurs were based on the size and shape of the pigment vessels. That tells us that the feathers of a lot of these first dinosaurs with wings were really flamboyantly colored. These were not drab animals.

                           These were not your Jurassic Park dinosaurs. These were ornate, gaudy dinosaurs. Some were white and black and brown and some had alternating colors. Some were iridescent. Some even had ginger feathers. Some had ringed tails like raccoons. So, that provides some additional evidence that wings may have first evolved for display and, only later, were they co-oped as air foils.

Mirsky:               The shape of the melanosomes revealing the color is based on comparisons with modern birds?

Brusatte:            That's right. That's right. So, it was less than a decade ago that a really clever grad student at the time, Jakob Vinther, who wrote an article for Scientific American, last year, I believe, on this very subject, he – while he was still a student, he realized that you can get these pigment vessels preserved in fossils. By doing a lot of comparisons with modern animals, he determined that you can statistically tell the color based on the pigment vessels by measuring the size and the shape and putting them into big multi-variant data sets. So, yeah, the long and short of it is if you have the feathers preserved, if they're preserved well enough they have the pigment vessels and you can measure those things, you can predict the color of your dinosaur.

Mirsky:               That's great. You spend some time in the book talking about the dinosaur lungs. That's really fascinating. So, can you share some of that info?

Brusatte:            Yeah. Dinosaur lungs, this is something you wouldn't think we would have any idea about. How could you possibly get a lung preserved as a fossil? They're some of the softest bits of the body and they decay so quickly. But, in dinosaurs, we know something about the lungs. It's not because we have the lungs, themselves, fossilized. I don't think a dinosaur lung has ever been found, as far as I know.

                           But there are some structures that extend from the lungs, not in mammals, not in amphibians, not in reptiles, but in birds today. Birds have lungs that have these air sacs extending out of them. These air sacs are basically balloons and they fill up with air as the bird breathes in. They store some of that air, still full of oxygen, which they can then pass across the lungs when the bird breathes out. So, this helps birds take in oxygen during both inhalation and exhalation, which is an amazing feat of evolutionary engineering.

                           Dinosaurs have the same system. How do we know it? Well, those air sacs leave marks on the bones. Those air sacs are so packed into the body that they extend into the bones, in some cases. We can see in fossil dinosaur bones, the holes in the bones, particularly of the backbone, the vertebral column, where the air sacs would have gone in. Then we can look inside the bone either by cutting it open or by CAT scanning and we can see the chambers inside filled with these air sacs.

                           It's the exact same type of anatomy in birds today. Mammals don't have this. Nothing else has this. So, by the marks left on and in the bone, we can tell that dinosaurs had these hyper-efficient bird-like lungs.

Mirsky:               What does that enable them to do?

Brusatte:            It enabled them, probably, at the very least, to breathe very efficiently, taking in oxygen when you breathe in and when you breathe out. It seems crazy and it's all because of the air sacs storing some of that oxygen-rich air so it will pass across the lungs when you breathe out. That's a big deal. You basically get twice the bang for your buck.

                           So, this is one of the reasons that modern birds can fly. You need a lot of energy to fly. You need to take in a lot of oxygen. So, these efficient lungs make it happen. Some birds, like some big albatrosses, for instance, or big vultures, they can high really high up. They can fly up in the Himalayas, many tens of thousands of feet. So, it helps more efficient breathing at those kinds of altitudes.

                           For the dinosaurs that evolved these lungs, why exactly the evolved them is hard to say. But I think, in general, it's probably a good thing if you can get twice the amount of oxygen while doing the same amount of work.

Mirsky:               It's one of the factors that enabled them to get so big?

Brusatte:            That probably was also the case. So, the very biggest dinosaurs of all, the giant sauropod dinosaurs, some of these things got to be as big as Boeing 737s, which is nuts if you think about it. I mean, my goodness, some of these dinosaurs were more than 100 feet long. They weighed more than 50, 60, maybe even 70 tons. That is generally the size of a Boeing 737.

                           But these dinosaurs weren't a building. They weren't a statute. These were real animals. They had to hatch from an egg. They had to grow up. They had to move around. They had to breathe. They had to eat.

                           So, how does evolution make something so big? Well, it doesn't seem like there's just one reason why dinosaurs got big. It seems like there were a bunch of different reasons that, when put together, allowed some of these long-neck dinosaurs to become truly huge. One of those reasons is the lungs. Because the lungs had those air sacs, those air sacs could hollow out the bones. That saved a lot of weight. It saved a lot of bulkiness.

                           So, it means that these dinosaurs can have relatively light-weight skeletons that they can still move around, that are still strong and still flexible, but light-weight. That helped them get bigger and bigger and bigger. The same way that skyscrapers are getting bigger and bigger and bigger because of the internal support structures of skyscrapers, they're light-weight. They're not super bulky. So, it was similar with these dinosaurs.

                           So, mammals today don't have that. We don't have lungs that have air sacs. So, we don't have these air sacs that can invade the bone and lighten up the bone. That's why it looks like things that are kind of elephant size or a little bit bigger, that might be the limit as to where mammals, at least on land – if we're forgetting about whales for a moment because the water's very different. But at least on land, you can't really get mammals, it doesn't seem, to be the size of dinosaurs. I think the lungs is one of the main reasons.

Mirsky:               Yeah. It's not that lungs evolved so that the dinosaur could get big. It's that the lungs are there and dinosaurs that happen to be a bit bigger are able to survive. So, you get this direction of growth that is possible. It's not that there's a purpose to it.

Brusatte:            That's right. Evolution doesn't work with a purpose. Evolution doesn't work with foresight. It's only acting in the moment, the survival of the fittest in the moment. Whatever features that an organism inherits, whatever variable features that it has, if those things promote survival in the moment, then nature will select them. That's generally how evolution works in a nutshell.

                           So, evolution isn't going to be looking ahead 10, 20 million years saying, "Okay, if we evolve this lung now, later on we can make the neck longer and then we can make this part of the body stronger. Then we can, one day, become a huge dinosaur." It just doesn't work that way.

                           It's the same way with the evolution of flight. When the very first dinosaurs evolved feathers, when those feathers turned into wings, when the first wishbones evolved, all those things were happening for other reasons. They had nothing to do with flight. It was only much later that that Lego kit was kind of put together.

                           Now, all of a sudden, you had a small dinosaur with long arms, with feathers that it had probably evolved to keep warm, with wings that it had probably evolved for display, with a wishbone that it had probably evolved to help stabilize its shoulder and it was hunting. Now, this animal could start moving those arms a little bit. It was going to get some drag and it was going to get some lift by the laws of physics. Then, nature, evolution, could start working making that animal a more efficient flyer. But evolution wouldn't have known that at the beginning. It was something that just happened when the time was right, when enough kind of dominoes had fallen to get to that point.

Mirsky:               T. rex is such an iconic animal. It had feathers we now know.

Brusatte:            Yep. So, imagine a T. rex the size of a double-decker bus, 7 or 8 tons, a head as long as an average human is tall, 50-some railroad spike teeth that could bite so hard that they crunch through the bones of their prey. Then, imagine this thing covered in mangy-looking feathers. It is a weird image. It was really much more of a feathered, big bird from hell type of animal than it was the green, scaly, reptilian-looking picture in Jurassic Park. So, T. rex wasn't scary enough. Imagine it as this giant, mangy, big bird and dream about that.

Mirsky:               T. rex, I didn't realize this till I read your book, but T. rex just got in under the wire before the dinosaurs went out of business.

Brusatte:            That's right. T. rex was there when the asteroid hit. 66 million years ago, this 6-mile-wide asteroid travelling faster than a jet plane smashed into the earth with the force of over a billion Hiroshima bombs that punched a hole into the crust that was over 100 miles wide. This unleashed a catastrophic chain reaction of destruction. Wild fires and tsunamis and super volcanoes and earthquakes and hurricane-force winds and all the dust blocking out the sun. These things reshaped the Earth within a matter of moments and then days and weeks and months.

                           Dinosaurs, most dinosaurs couldn't cope. One of those dinosaurs was T. rex, itself. T. rex was there when the asteroid hit. Triceratops was there when the asteroid hit. There were duck-billed dinosaurs. There were armored dinosaurs, the ones that looked like tanks. There were the head-butting dinosaur, the pachycephalosaurs. There were long-neck dinosaurs.

                           All of these dinosaurs were there and they would have seen that flash of light streak across the sky and they would have had to deal with the immediate aftermath of that Earth-changing event. It was probably the worst single day in the history of Earth. It changed. Everything changed and it was a hinge point in history. The dinosaurs, they were at the top of nature but they were struck down maybe at their prime, it looks like. A few birds made it through. So, dinosaurs did continue. But not so much as an empire anymore. But now mammals had their chance and they took advantage of it.

Mirsky:               So, T. rex had only really existed for a couple of million years. Then they went out with everybody else. But there were T. rex–like animals that had been around for far longer, the things that if you saw them and you didn't realize they were probably smaller than T. rex you might assume were T. rex.

Brusatte:            That's right. T. rex is the last surviving member of this group of dinosaurs, this group of meat-eating therapod dinosaurs called, very originally, the tyrannosaurs or the tyrannosauroid in the formal scientific parlance. Most tyrannosauroids, or most tyrannosaurs, let's say, were not giant apex predators. Tyrannosaurs got their start a good 100 years before T. rex, way back in the middle Jurassic. They started off small. They started off humble.

                           We've seen this pattern before. It was the same with tyrannosaurs. The first ones were human-size or smaller. Some were even just the size of dogs and they were living in the shadows. They were second or third tier predators living with other giant, meat-eating dinosaurs; the allosaur, the carchardodontosaurs, the spinosaurs, the ceratosaurs, those types of dinosaurs. For a good 80 million years or so, that's how tyrannosaurs stayed. That was that.

                           But then, while they were living in the shadows, they started to get bigger brains. They started to get keener senses, probably so that they could survive in that sort of world, survive underneath all these other big predators. Then when some of these other predators went extinct – we don't really know why; sometime in the middle cretaceous it happened – the tyrannosaurs had the opportunity to seize the crown and they did it. They, very quickly, became these huge apex predators, the size of buses.

                           It may have been evolving the big brains and the keen senses at smaller body size that helped them take control. So, at the very end of the time of dinosaurs, you had these giant tyrannosaurs like T. rex and these things had both brains and brawn. That made them the ultimate dinosaur predators.

Mirsky:               You just came in from some field work in Scotland, where you're based. What are you looking for? So, we think of dinosaurs as coming mostly from China or the North American West. But you're finding things in Scotland, too.

Brusatte:            Yep. So, we're just back from a trip out to some of the Scottish islands, some of the little islands off the west coast of Scotland in the icy waters of the North Atlantic. These are dinosaurs we can find there that lived in the middle part of the Jurassic period. So, right around the time that the very first tyrannosaurs were getting started, right around the very first birds were probably evolving, right around the time that the sauropod dinosaurs, the long-neck ones, were becoming truly enormous. Surprisingly, there are not that many fossils of this age from anywhere in the world.

                           But Scotland is one of the few places. It's only on these little islands, particularly the Isle of Skye, this enchanting place, this Tolkien-esque landscape of craggy peaks and sheer ocean cliffs and tidal platforms and lots of rain and mist and wind. But it is a great place to find dinosaurs. We're finding more and more, the more we look. We do find bones and teeth. But a lot of what we're finding are footprints, lots and lots of dinosaur footprints, tracks made by some of these enormous long-neck dinosaurs, ones that were probably about 10 or 15 meters long that weighed about 10 tons or so. Tracks of some of the meat-eating dinosaurs including maybe some primitive cousins of T. rex.

                           We're starting to get glimpses maybe of some other types of dinosaurs as well. So, it's a really neat thing to have here in Scotland. It's a beautiful place to work. The weather doesn't always cooperate. But it is just a really magical thing to go out on these kinds of mystical Scottish coasts in the shadows of ruin castles and find dinosaur footprints. It is an indescribable sort of feeling.

Mirsky:               That's great. So, what do we get by considering birds as being the last dinosaurs that still exist versus our previous view that birds are birds?

Brusatte:            It means that dinosaurs are still with us. They're still with us in the guise of birds. It's not the same as T. rex terrorizing people in the streets of Edinburgh or brontosaurus thundering across the National Mall Washington, or whatever image you want to conjure up. But dinosaurs are still with us. The empire has ended, but the dinosaurs still remain, in the same way that there's probably some descendants of Charlemagne or some descendants of some of the French monarchs that are still around even though they're not in power.

                          It does mean that the world of dinosaurs continues to today, that that world does help shape our modern world. There are 10,000-some species of living dinosaurs, animals that have dinosaur DNA, that have dinosaur blood coursing through their veins. These animals are every bit as much dinosaur as a T. rex is or a Brontosaurus is. We should really think about them the same way we think about bats. Bats are a strange type of mammal that evolved wings and developed the ability to fly. Birds are a strange type of dinosaur that did the same thing.

                           I think that is neat. It shows there's a connection between the modern day and the past. We're all part of the same story. That's one of the things I want people to hopefully grasp when they're reading my book is that this is one, big story. The Rise and Fall of the Dinosaurs was the story of an empire and that was the empire that ruled the Earth before our empire. But all of this stuff is connected together. We all live on this one planet, this old, vast, very fragile but also, in many ways, very resilient planet, a beautiful planet, a planet with a long, rich legacy and a planet that, hopefully, we can continue to live on for quite a long time yet.

Mirsky:               That's it for this episode. Get your science news at our website, www.ScientificAmerican.com, where you can check out our continuing coverage of the Kilauea volcano in Hawaii. I heard a New York City local reporter say last week that lava was erupting 30,000 feet into the air. I'm pretty sure that if that were happening it would signal a worldwide catastrophe. In fact, it was ash and smoke that was rising that high. Lava was staying much closer to the ground, thankfully.                

                           Follow us on Twitter where you get a tweet whenever a new item hits the website. Our Twitter name is @sciam. For Scientific American Science Talk, I'm Steve Mirsky. Thanks for clicking on us.

Voice:                 Liquid hot magma.