The long history of birds, from velociraptors to pigeons

IRA FLATOW: Hey, it’s Ira Flatow. And you’re listening to Science Friday. Birds are dinosaurs. It’s something we hear a lot from experts, especially if you listen to this show. But you’ve got to admit that looking at a backyard sparrow does not quite evoke the same awe as the dino bones in the museum do, right?

Well, my next guest urges you to just get over it, rethink birds, and give them the same credit as their fearful ancestors. Steve Brusatte is a paleontologist and author of the new book, The Story of Birds a New History from Their Dinosaur Origins to the Present. He’s based in Edinburgh, Scotland. Welcome back, Steve. Good to have you back.

STEVE BRUSATTE: Always a pleasure, Ira. I’ve loved chatting about dinosaurs and fossils on the show over the years. And I’m, of course, excited now that we’re going to be talking about dinosaurs and birds together.

IRA FLATOW: I think of you more as a dinosaur guy, as we have talked over the years. Why change, suddenly, your focus to birds?

STEVE BRUSATTE: What it comes down to is that today’s birds are real, true dinosaurs. And by that, I’ll just be very direct about it. They are part of the dinosaur family tree. They evolved from other dinosaurs. And yes, a sparrow, a pigeon, a gull, it looks nothing like a T Rex or a brontosaurus. But we humans are mammals. We look nothing like an elephant or a whale.

We are just one of many mammals. And the same is true of birds. They’re one of many types of dinosaurs. And really, the way we need to think about birds is the way we think about bats. Bats are a mammal. Of course they are. They evolved from other mammals. They have all the classic features of mammals, hair, and molar teeth, and so on. But they’re just a strange mammal that got small, evolved wings, developed the ability to fly.

And birds are the dinosaur equivalent of that. And right now, I’m in my office in Edinburgh. As we’re chatting, I have a big window in front of me. There is a pigeon out there. And although it might seem weird, that’s a dinosaur as much as a T Rex or a brontosaurus is.

IRA FLATOW: Never more you might say to that pigeon. So how does the evolution work? Give us an idea here, because not all dinosaurs became birds, right?

STEVE BRUSATTE: That’s right. The story of the evolution of birds, to me, is really fascinating. It’s not a story of a T Rex mutating into a chicken through some chance genetic accident. No, no, no, no, no. We see in the fossil record, a whole series of transitional fossils. Not every single species, but we see a lot of the species, step by step, the dinosaurs that evolve the classic features of birds, whether it’s feathers, wings, wishbones, hollowed out bones, big chest muscles for beating the wings, these things evolved one by one in a whole series of dinosaur ancestors over tens of millions of years before they were repurposed into a flying machine.

And that is really the story of bird evolution, a long, gradual evolution from their dinosaur ancestors. And as a paleontologist, the fact that we have fossils of dinosaurs covered in feathers, raptor dinosaurs, that just still blows my mind, that we have the evidence to study this and understand this from millions of years ago.

IRA FLATOW: But didn’t we already have flying dinosaurs like archaeopteryx? I mean, were they not birds? Or what’s the difference in the definition?

STEVE BRUSATTE: Well, this is where we get into nomenclature, and names, and classification. But I’m sure everybody listening to the radio or listening to the podcast wants to hear the legalistic arguments. What makes a bird a bird?

When it comes down to it, bird is a vernacular term. And we know a bird when we see one today. And where we pin that word on which fossil is a little bit up to you. But for me, a bird is an animal that has feathers. Feathers make up a wing. And it can use that wing, it can flap that wing to generate lift, and thrust, and fly through the air.

Or it’s like an ostrich or a penguin that lost the ability to fly, but had ancestors that could do it. So by that definition, there were lots of dinosaurs that had feathers and even had wings. I mean, my goodness, Tyrannosaurus had feathers.

But it was archaeopteryx, about 150 million years ago, that is the oldest fossil of an animal that we can call a bird, in the sense that it had wings made of feathers. Those wings were big enough. They could move in the right way that they could generate lift, generate thrust, get that animal into the air. So that means that there have been real, honest to goodness birds for at least the last 150 million years.

But these first birds, like archaeopteryx, they didn’t look exactly like the birds of today. They really looked like a half dinosaur, half bird, some kind of Frankenstein creature. They still had teeth in their jaws. They still had claws on their hands. They still had long tails.

So they looked kind of like a velociraptor with big wings. And that’s because these fossils really do capture evolution in action. They are transitional fossils. And they show us how dinosaurs were taking to the skies and becoming a new type of animal.

IRA FLATOW: Well, if velociraptors, for example, had feathers, why didn’t they just develop wings and fly?

STEVE BRUSATTE: Great question. And the thing is, velociraptor had feathers. And velociraptor, believe it or not, but it’s true, actually had wings. We know this from fossils.

IRA FLATOW: Really?

STEVE BRUSATTE: It did. And I’m not just guessing this. I’m just not making some assumption. We know from fossils. Now, those wings, however, were small. The Raptor dinosaurs, or at least most Raptor dinosaurs, actually had wings.

We don’t see them all the time as fossils. Normally, the feathers decay away quite quickly. You need really a one in a trillion circumstance to bury a dinosaur and fossilize the soft bits like feathers. But we have fossil sites where this happens, usually because these dinosaurs were buried by volcanoes, kind of like Pompeii. And so you get the soft bits locked in.

So you see, a lot of raptors had wings. But those wings were too small to fly. And a lot of other dinosaurs had feathers. I mentioned Tyrannosaurs had feathers. But those feathers were really simple. They didn’t even form wings. They just looked like little hairs, little fluffy strands.

So what we see through the fossils is quite clear, that feathers, and even wings, first evolved in distant dinosaur ancestors of birds. They did not first evolve in birds. They did not even first evolve for flying. They probably evolved for a whole host of things. Simple feathers, maybe to help keep the bodies warm, the same way we have hair.

The wings, we think, may have started as display structures, as advertising billboards sticking off the arms of these dinosaurs to attract mates, to intimidate rivals. And then really, just by accident, by happenstance, some of these billboards became big enough that when these dinosaurs moved them around, just by the laws of physics, they provided a little bit of lift, a little bit of thrust. And those dinosaurs could start playing around in the air.

And that is when the threshold was crossed. These dinosaurs could start to fly a little bit, again, just by happenstance. And that is how evolution works. Evolution doesn’t plan ahead. Natural selection works in the moment to shape organisms to their own time and place. And it’s out of that crucible of natural selection over millions of years that some dinosaurs took to the sky. And those dinosaurs have managed to hold on till today, when no other dinosaurs have.

IRA FLATOW: Well, is it because those big dinosaurs died out after that the collision on Earth and the little ones survived? That’s why the birds we have are smaller?

STEVE BRUSATTE: This is something that fascinates me. Why did birds survive when all the other dinosaurs died? And for a long time, I think this was one of the biggest mysteries in all of paleontology. And I think now, we have a much better handle on it. We might not understand it completely, but we have a much better handle. There’s been a lot of interesting research recently.

Back in the autumn, we had a new study, my colleagues and I, about the extinction of the dinosaurs, the asteroid, how quickly it changed the world and led to upheaval, which killed off 75% of all species. If you were alive that moment the asteroid came out of nowhere and smashed into the Earth, if you were alive that moment, your entire species had only a one in four chance of surviving.

And the earthquakes, the wildfires, the volcanic eruptions, all of this carnage that was triggered by the asteroid, it led to global destruction. I mean, it sounds hyperbolic. I know what I’m sounding sounds like a bad disaster movie, but it really happened.

And what we see in the fossil record is that everything that lived on land that was bigger than a husky dog, it died, gone forever. So that’s why the T Rex’s, the triceratopses, why they died. Probably because they didn’t have enough food to eat. They couldn’t hide away very easily from the fires, and the earthquakes, and so on.

So you had to be small to survive. But beyond that, what’s really interesting is that a lot of birds died as well, except for modern style birds, the ones that grow really fast from a baby into an adult, the ones that have beaks instead of teeth.

And we think that those two features in particular were so important. Because if you could grow fast, that means that you could reproduce fast. You could turn over the generations quickly. And if you had beaks, you could eat seeds, which might seem trivial.

It might seem trivial, but something as random as being able to crack open a seed, that might have been your ticket to survival when the world changed so quickly because the forests collapsed. The sun was blacked out for years from all the soot, from the fires, from all the dust and grime from the asteroid collision.

Photosynthesis shut down. Trees couldn’t make their own food, nor could other plants. And so the ecosystems collapsed. And if you were the type of animal that ate part of a living plant, leaves, or fruits, or flowers, or what have, you were in big trouble. You were in big trouble, really big trouble.

But there’s one type of plant– one part of a plant that we know, today, survives longer than any other. If there’s a volcanic eruption that obliterates an island, if there’s a big wildfire, seeds will remain in the soil for quite some time. And if you can eat those seeds, you might have access to the last available food source.

It won’t get you through forever, but it can maybe get you through for a few years. So we think now that being able to grow quickly and being able to eat seeds with their nutcracker beaks were two of the random things that just so happened, by happenstance, to allow birds to stare down the asteroid and survive when no other dinosaurs did.

And if it wasn’t for that, birds probably would have gone the way of T Rex and triceratops. And we wouldn’t have birds in the world today. And to me, it is just wild to think about those what-ifs of history.

IRA FLATOW: And if the seeds had survived long enough, let’s say, a year or two in the ground, could they have sprouted and had been an additional source of food?

STEVE BRUSATTE: Probably so. And probably that’s the reason why the world didn’t just totally end. Forests did regrow eventually. And what we think now is that it probably was a few years where the Earth went dark and cold.

We don’t for sure. We weren’t there to see it. But we have the evidence in the rocks. We actually see the soot and the charcoal from the wildfires, for instance. And we see a huge decline in plants and so on. And so the best estimates are that at least for a few years, it would have been like a global nuclear winter.

But of course, trees did come back. And they came back because seeds do last for a long time. That is part of the survival strategy of plants. And for birds, and really for the entire dinosaur family, birds were the only dinosaurs to make it through, just to think that it came down to something that seems so basic, so trivial. I mean, it really, really is.

IRA FLATOW: We have to take a quick break, but don’t go away. More on this when we get back.

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IRA FLATOW: I’ve got a speed round for you.

STEVE BRUSATTE: OK.

IRA FLATOW: OK? Because I know between the asteroid and now, we had 66 million years of bird evolution. And I know there are some really weird– I’m going to say, weird sounding birds and scary birds, let’s start with this flashy name, the demon duck. Sounds like a Disney character or something.

STEVE BRUSATTE: It sounds like a Disney character from some kind of spin-off horror film. The demon ducks are one of my favorites. They are not around anymore, but our human ancestors– actually, not even our ancestors, members of our species actually met the demon ducks. They only lived in Australia. And when the first humans came to Australia, they would have been confronted with these enormous birds, 100 times the size of a modern day duck.

They weighed more than 500 kilos, more than 1,000 pounds. They were monstrous animals in size, but their nicknames a little bit unearned and unfortunate because they were not demonic. They were gentle plant eaters. They were actually the biggest plant eaters at the base of the food chain for tens of millions of years in Australia, before they sadly went extinct not long after humans met them.

IRA FLATOW: Wow, OK. I know there’s another scary sounding terror birds. How terrible were they?

STEVE BRUSATTE: Now, these ones deserve their nickname and then some. They lived in South America. And they lived in South America for tens of millions of years. And they were basically T Rex born again. These were dinosaurs, of course, because they’re birds, that after the asteroid, they lost the ability to fly.

They gave up the ability to fly, like many birds do. And as a trade-off, that allowed them to get bigger. And they became the top predators. They literally were filling that ecological niche that was left behind by the giant meat eating dinosaurs like T Rex.

And these terror birds, they stood taller than a human. They had heads the size of a horse’s head with this nasty, gnarly, sharp beak at one end. They had these big, robust, muscular feet capped with ferocious talons. They were kickboxers. And they were flesh slicers. And they were the top predators in South America. And they briefly, ever so briefly, made an incursion into North America. But they didn’t last very long because this was really just right around the time of the last Ice Age.

IRA FLATOW: Oh, so the Ice Age wiped them out?

STEVE BRUSATTE: Yes, we think so. Which is probably a good thing because we would not– this is like think of Big Bird, but think of Big Bird as an animal out to get you. And there, you got a terror bird.

IRA FLATOW: Well, speaking of big birds, the next up– and I was thinking about this before when you talked about birds, about dinosaurs that had feathers and wings and just couldn’t fly, and now I heard in your book, the giant penguin. How giant are we talking about?

STEVE BRUSATTE: We are talking about really giant penguins. Now, I have a six-year-old son at home, Anthony. And if you ask him his favorite dinosaur, he will tell you right away, penguins, which is great. It means I’ve taught him well that birds are dinosaurs.

But if you ask him even more, which penguin is your favorite, he will tell you, as he’s told every kindergartner in the city of Edinburgh, I think, that it’s the colossus penguin. And this is an extinct penguin. It lived many tens of millions of years ago in the Southern oceans.

It was literally, I promise, I swear I’m not making this up, it was literally a penguin the size of a gorilla. And to me, it reminds me of one of those things in the Beatles Yellow Submarine video, You got that psychedelic scene, I picture the colossus penguin there.

These were top predator penguins. This was right after the asteroid cleared away the mosasaurs, and plesiosaurs, and those toothy reptiles that once ruled the waves when dinosaurs were on land. Now, eventually, big sharks and killer whales would come and take over that top predator niche in the oceans.

But for this glorious moment of time, at least in the Southern hemisphere, it was enormous penguins that were the top predators and fish eaters. And we have their fossils. Their fossils are massive. Again, these are taller than a human, weighed as much as a gorilla.

Imagine the biggest penguin you’ve ever seen at a zoo and just beef that up. And these animals really lived. We would never about it– this is a great example, we would never about them if we didn’t have the fossils. The fossils are stunning.

IRA FLATOW: Yeah, let’s turn the clock ahead a little bit to more present eras. I know you study extinctions and what comes before and after them. And as we have been following over the years, birds are facing multiple threats. In North America, the number of breeding birds has declined by, what, 3 billion in the past 50 years? Is this an extinction that we’re facing, Steve?

STEVE BRUSATTE: It did get a little bit depressing reviewing these numbers for the number of bird species that have gone extinct quite recently. And not just that, as you say, it’s not just about total number of extinctions.

Extinction is forever. Extinction happens, that species is gone forever, which is, of course, is depressing and terrible. But you can have a species that was once thriving, that has been decimated, that’s still holding on. And that’s what’s happening to a lot of birds.

And I talked to my parents about this. And I tell them these facts that in the time since you graduated high school, this would have been around 1970 or so, there’s been a standing loss of many billions of birds in the standing population of just North America alone.

And that’s because of pesticides. It’s because of climate change. It’s because of what we build as humans, and how we move around, and how we affect the environment. And it’s not just back home in North America. It’s here in Britain as well.

Since the time that my six-year-old Anthony was born, there has been a 50% loss in the standing diversity, the standing numbers of several of the key species of hedgerow birds and farmland birds. Now, is that a momentary blip? Or is this a longer term pattern that’s emerging? It’s hard to say.

And I don’t mean to be too pessimistic, but I think we do need to acknowledge that a lot of birds have gone extinct, completely, since humans began moving around. And things like dodos are the emblems of that. But at the same time, there’s two things that make me feel positive.

One is that when we have realized that our activities are harming certain birds, we’ve done something about it. The California condor, the bald eagle are the best examples. When I was growing up in Ottawa, Illinois, in Northern Illinois in the late ’80s, early ’90s, we hardly ever see bald eagles.

By the end of the ’90s, they were so common around the Illinois River that now out at Starved Rock State Park, where I’m from, these are like winter vacation packages. Go see the eagles. So they have recovered because we have made a point to conserve them. So that gives me hope.

The other thing that gives me hope is, let’s face it, birds are survivors. Birds are survivors. Birds stared down that asteroid. That asteroid took down T Rex, the most iconic extinct species ever. That asteroid took down triceratops. It took down the long-necked dinosaurs.

Birds survived. And birds have proven over the 150 million years they’ve lived, that they can deal with climate change, and environmental change, and rising and falling sea levels, and changing temperatures. That’s not to say that we should go nuts and destroy habitats of birds and birds will be OK. No, no, not at all.

But I do feel, actually, in many ways more confident about the future of birds than I might about the future, let’s say, of us. And I’m not being pessimistic there. I’m just saying birds are incredible. They are survivors. Birds are smart. Birds are incredibly smart. They are adaptable. And they can do something we can never do. And that is they can fly.

And if you cause them any trouble, they could just fly away from any immediate danger. I think we need to celebrate birds more and just really cherish how incredible they are. And whenever we look at a modern day bird, I want people to realize that they’re looking into the face of a real, live dinosaur.

IRA FLATOW: Well, Steve, they will when they read your book. We have run out of– we could go on forever. We’ll save it for the next conversation.

STEVE BRUSATTE: For the next book.

IRA FLATOW: This is a great book. Steve Brusatte, paleontologist and author of The Story of Birds a New History from Their Dinosaur Origins to the Present. Steve is based in Edinburgh, Scotland. This episode was produced by Kathleen Davis. And if you have nightmares about demon ducks and terror birds after listening to this, give us a call, 877-4SCI-FRI. We’ll see you next time. I’m Ira Flatow.

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