The dinosaurs who survived the asteroid
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What event led to the extinction of most dinosaurs?
This is The Guardian.
It was the most cataclysmic event in the Earth's history.
The asteroid came down and the dinosaurs died, but there was one peculiar type of dinosaur that did make it through.
Yes, one type of dinosaur is miraculously still around today.
My wife and I were at the Lyme Regis fossil festival and we had a little break and we were sitting by the beach and I was eating a pasty and one of these aerial assassins from the sky came down and stole my pasty. It was not pleasant. I was very hungry. My lunch was gone. It was just a sad scene.
That's right, girls.
How are birds classified as modern-day dinosaurs?
And every other bird, too. Birds are, in fact, dinosaurs.
This is not a turn of phrase. This is not scientists tweaking the definition of words that you thought you knew so we sound smarter. This isn't us hinging on some technicality. It's actually really straightforward. Today's birds evolved from dinosaurs.
It's estimated that there are just over 6,000 species of mammals around today. But birds? 10,000 species.
What evidence shows how birds evolved from dinosaurs?
So in that way, the age of dinosaurs actually continues.
So how did birds evolve from their reptile ancestors into our feathered friends? And if they survived the asteroid, can they survive us? I'm Nicola Davis, Guardian science correspondent, and this is Science Weekly.
Birds are dinosaurs. And I want people to understand what that means.
Professor Steve Brussati is a paleontologist and evolutionary biologist at the University of Edinburgh. And he's the author of a new book, The Story of Birds, an evolutionary history of the dinosaurs that live among us.
They are a strange type of dinosaur that millions of years ago got small, evolved wings, developed the ability to fly. They are part of the dinosaur family tree.
How did feathers evolve from scales in birds?
They are part of the bloodline.
Scientists estimate that somewhere between 165 million and 150 million years ago, birds first appeared. The oldest known bird that's so far been discovered is the Archaeopteryx. To picture this fossil, imagine the imprint of a bird that's flown very hard into a window.
It is a transitional fossil. It has feathers. It has big wings. It has a wishbone. It has hollowed-out bones, just like birds today, but it still has teeth in its jaws. It has long, sharp claws on its hands.
What adaptations helped birds survive the asteroid impact?
It has a long, skinny, bony tail. It's very much a half-reptile, half-bird. But it could fly. It was essential to Darwin's theory of evolution. It was one of the fossils that really proved evolution to the masses back in the 1860s and 1870s. And it remains today still the oldest known bird in the fossil record.
Since the 1800s, more and more evidence has accumulated.
We have enough fossils of dinosaurs in different stages of this transition that we can see, generally speaking, how evolution took a dinosaur and turned it into a bird. And the thing that's immediately clear is that this didn't happen quickly. It was gradual.
What role did beaks play in the survival of birds?
It was a long process.
What's the most iconic feature of birds? Their feathers.
So where did these come from? Feathers have basically evolved from something like a scale. You can tweak a feather in a bird as it's growing in an embryo and actually turn it into a scale or vice versa. And you see this when you look at a chicken, you know, his body is covered in feathers, but look at those scaly feet. So there is this intimate relationship between feathers and scales.
Evidence for the relationship between feathers and scales isn't just found in the fossil record.
We now know from the genetics birds are more closely related to crocodiles than crocodiles are to lizards or snakes or turtles.
How have human actions impacted bird populations today?
So birds are nested, they're ensconced within the reptile family tree. They are a heavily modified reptile. This is simply based on what we know today and the DNA of animals today. And it is some of the strongest, most convincing evidence out there for anybody who maybe is doubting, could birds really have evolved from dinosaurs? Are birds really some type of weird reptile? How do you get a bird from something like a lizard or a crocodile? Look at the genetics. Birds are smack right in the middle of that reptile family tree.
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Chapters
8 chapters
1
What event led to the extinction of most dinosaurs?
0:00–1:00
2
How are birds classified as modern-day dinosaurs?
1:00–1:33
3
What evidence shows how birds evolved from dinosaurs?
1:33–2:31
4
How did feathers evolve from scales in birds?
2:31–3:05
5
What adaptations helped birds survive the asteroid impact?
3:05–3:53
6
What role did beaks play in the survival of birds?
3:53–4:42
7
How have human actions impacted bird populations today?
4:42–5:22
8
What is the future outlook for bird species in the current environmental crisis?
5:22–17:09
Speakers
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