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Of all the animals that live on our planet, one extraordinary group dominates. It has produced the largest… the fastest, the most intelligent creatures that have ever lived. They are known as vertebrates and they all share one vital feature – a backbone. I am travelling back in time to look for the key advances that drove their remarkable success.

So far, I have seen the vertebrates grow from tiny origins to dominate the oceans, colonise the land… and take to the skies.

Macaque, monkeys are vertebrates
Macaque

In this program, I will track the rise of a whole new branch of vertebrate life. They are the most complex animals yet to appear on Earth.

They started as a group of tiny little creatures scarcely bigger than my little finger. Nocturnal animals. But they were to develop into some of the biggest creatures the planet has ever seen. It’s a group that also contains us. This is the story of the mammals.

I want to investigate how the mammals acquired a new set of key features that allowed them to thrive in every corner of our planet. Features we also have inherited. We’ll find the evidence in a series of thrilling fossil discoveries and in living animals.

Yunnan Province
Yunnan Province

With the latest scientific analysis, we will be able to bring our ancient ancestors back to life.

Vertebrates: Animals with backbones

Today, animals with backbones dominate our planet on land, in the air and at sea. But how did that evolutionary takeover come about? There have been lots of gaps in the story. But in recent decades, exciting new discoveries have been made here in China, and I’m here to look at them.

The rocks of China are yielding up the elusive missing links in the vertebrate’s story. Ancient creatures are preserved as fossils. To find new evidence from the very start of the mammals’ story, I’m travelling to the South of China, and the province of Yunnan.

Dinosaur Fossil vertebrates
Dinosaur Fossil

Fossils found here can reveal the kind of world those first mammals encountered, and the kind of animals they had to compete with to gain a foothold and survive. This area of southern China is known as the Lufeng Basin, and 180 million years ago, it was a vast natural hollow into which waters from all the surrounding hills flowed. And with those streams came sediment, which is now this; clay, and they also brought the bodies of the animals that lived in those hills, including creatures like this one – a dinosaur.

Excavators have uncovered hundreds of specimens like this one in the surrounding countryside. The local museum is crowded with one of the largest collections of complete dinosaur skeletons in the world.

But unique discoveries here have revealed some of the earliest evidence for the origins of the animal group that would eventually succeed them.

At the same time, the dinosaurs were roaming in this area, there was another very different creature evolving in their shadow. One that was on a much, much smaller scale.

The Successor to the Dinosaurs

Palaeontologist Wang Tao has spent his life exploring these hills. He’s used to finding the remains of large dinosaurs. But on this hilltop site, he and his colleagues discovered something that didn’t match the usual profile.

Wang Tao
Wang Tao

Wang Tao “I came to collect fossils with my colleagues in this area here. At the time, it was not like this. There were no crops growing here. After looking around, we followed this little slope. And finally, we found a small fossil about 2 cm long. We thought it might be something special, so we sent it to the lab in Beijing to clean it up.”

Hadrocodium Fossil precursor to the vertebrates
Hadrocodium Fossil

I have travelled north to Beijing to see Wang Tao’s discovery for myself. It’s now stored in one of the world’s leading institutes for the study of fossils. And this is it. And what seems extraordinary, near miraculous to me, is that anybody should notice that a tiny, tiny little thing like this was actually a fossil. But a fossil it is. It’s the head of a tiny animal. There is the tip of its nose. That’s the back of its neck. And you can also see it’s got an eye socket. It’s called Hadrocodium. If I turn it upside down you can see the bottom of its jaw. It might be the skull of a really minute little reptile. But it’s not. Because reptiles have simple cone-shaped teeth, and this one has a tooth that is rather different. That has the shape of a little insect-eating mammal’s tooth.

So, this is one of the earliest mammal fossils we know of. And to that extent, it’s the ancestor of all mammals alive today, including ourselves.

Hadrocodium

As such, Hadrocodium holds a key position in the evolutionary story of the backboned animals, the vertebrates.

Evolutionary Tree
Evolutionary Tree

The first creature with the beginnings of a backbone lived over 500 million years ago. Then fish, amphibians and reptiles evolved.

It’s from the reptiles line that the first mammals emerge. The Hadrocodium fossil dates to 195 million years ago. These simple origins led to the vast diversity of mammals we see around us today. Over 5,700 living species have adapted to survive in every corner of the planet.

We humans dominate and are the most numerous of the large mammals.

This astonishing journey was built on a series of key evolutionary advances that began in very early forms like Hadrocodium. We only have its skull, but we can work out from modern mammals what the rest of its skeleton was like.

So, how did this minute animal, one of the vertebrates, gain a foothold in the age of the dinosaurs?

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Vertebrates: the animals with a backbone the Dawn of Mammals