There’s a reason we don’t have birds the size of elephants: the mysterious story of how dinosaurs evolved – expert Q&A |
Exactly how did birds evolve from dinosaurs? It’s a mystery that has been with us for more than 150 years, and palaeontologists are still hunting for pieces of the puzzle today.
Among them is the University of Edinburgh’s Professor Steve Brusatte, whose latest book, The Story of Birds, tells the whole fascinating story. We caught up with him recently to find out more.
Of all the great dinosaur subjects, why this story?
I’ve always been fascinated by birds. They are all around us and there’s such a stunning diversity and variety. As a palaeontologist I specialised early in the theropod (two-legged) dinosaurs. This is the group that includes T.rex and Velociraptor – and gave rise to birds.
The more I studied theropods, the more I became more curious about the modern-day animals that descended from them. Back in the early 2010s my PhD was about the origin of birds. Its core involved building a big new family tree of theropod dinosaurs to understand where birds slot in, how they evolved from dinosaurs, and how their body features came together.
I wrote about the dinosaur bird connection in my first book, The Rise and Fall of the Dinosaurs (2018), but that was just one chapter. It made me think it would be really fun to do an entire book on the subject. That was how my new book, The Story of Birds, came together.
Is there still any debate about birds evolving from dinosaurs?
I think people have generally heard that birds descended from dinosaurs. In the newer Jurassic World films you even see feathers on some of them. And yet it hasn’t really broken through to the public consciousness that today’s birds really are dinosaurs. They are part of the dinosaur family tree. They just happen to be a peculiar group of dinosaurs that got small and evolved wings, took to the skies and have survived until today.
It was Charles Darwin’s great disciple, Thomas Henry Huxley, in the 1860s who first noted similarities between the skeletons of some dinosaurs starting to be found in Europe and those of modern birds. This was back before anybody knew what DNA was, for instance.
Huxley’s idea did enter the public consciousness, at least in Victorian Britain. Darwin added it to the later editions of On the Origin of Species. But then it went out of favour. This was the great era of exploration, especially in the US and Canada. The frontier was being pushed westwards, and all these new dinosaurs were being found – Stegosaurus, Brontosaurus and later Brachiosaurus and T.rex.
Read more: The story of birds: a new history from their dinosaur origins – extract of Steve Brusatte’s new book
None look anything like birds. I think dinosaurs obtained this stereotype as giant reptilian monsters, and this still largely dominates the public consciousness today.
Yet there were also a lot of smaller dinosaurs. Many had feathers and wings, and many were very bird-like. It’s really only in the past few decades that the idea that birds evolved from dinosaurs has become scientific consensus. The discovery of feathers on dinosaurs in the 1990s really sealed the deal on that.
What mysteries remain?
There are of course still things we don’t know, like how dinosaurs started to fly. How did they start to move their wings in a way that generated enough lift and thrust to get them airborne? Did they run on the ground and use their wings to defy gravity? Did they do it from the trees down, using these wings as a way to manipulate gravity? That’s one of the biggest mysteries.
Another area of uncertainty is which dinosaurs were the closest relatives of birds. The more fossils we find, especially feathered dinosaurs in China and other places, the more it’s clear there was a whole bunch of small dinosaurs with feathers. A lot had wings, some had wings only on arms, some on arms and legs. Some had wings of feathers. Some had wings of skin like a bat.
There was a huge diversity of them right around that point in the family tree where proper modern-style birds evolved with big arm wings that they flap to keep airborne. Each new fossil gives us more information but also another layer of complexity. It makes it just a little trickier to untangle the knot of exactly which dinosaurs were the closest rivals of birds. You still see new discoveries being made every year.
You say in the book that wings evolved not to fly?
The fossils tell us clearly that feathers evolved long before any of these animals were flying. Many dinosaurs had simple feathers; they looked like little strands of hair. In fact most dinosaurs probably had them – they just........