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For millions of years, mammals remained the small, shrew-like creatures that we’ve encountered so far, skittering about around the feet of the dinosaurs. But then came a sudden global catastrophe that threatened to bring the whole history of the vertebrates to a sudden end. A cataclysmic meteor impact that would shroud the world in darkness.

A meteor impact that sent shockwaves around the world, and coincided with the extinction of the dinosaurs.

We are still not exactly sure why the dinosaurs disappeared, but certainly, 65 million years ago, they disappear from the fossil record. But many other vertebrates survived, and for them, the dominance of the world was now up for grabs.

Meteor Impact
Meteor Impact

Scientists are unearthing stunning evidence in Germany of how the mammals seized this opportunity. This natural hole is known as the Messel Pit. An entire community of animals was entombed here by an extraordinary freak of nature.

47 million years ago, this was a lake fringed by a subtropical rainforest.

A Cataclysmic Meteor Impact

But its waters held a dark secret. The lake was in fact a flooded volcanic crater. It’s thought that lethal carbon dioxide gas was released from its depths and periodically bubbled to the surface, killing the creatures that drank at its shore or flew over its waters. Their bodies drifted down to the bottom to be entombed in the muddy sediment. It’s now one of the most remarkable fossil excavation sites in the world.

Messel Pit sfter the meteor impact
Messel Pit

Painstaking work is uncovering creatures sealed inside layers of the ancient lake bed. They are preserved in extraordinary detail.

It’s a unique snapshot of life after the dinosaurs. There are reptiles, like lizards and snakes. Here, too, are ancient birds, the vertebrate group that evolved from the dinosaurs. But the biggest changes are amongst the mammals. They have started to specialise.

Bird Fossil
Bird Fossil

This, perhaps, is the least specialised of them. It’s an insect-eater, a creature like a large shrew, and its teeth are still relatively simple. But then there are also animals like this. And this has very big, gnawing front teeth. This is an early rodent, a creature like a rat.

Shrew Fossil fatality of the meteor impact
Shrew Fossil

And then bigger still… is this animal. This has grinding molar teeth at the back and long legs. It’s beginning to stand up on its toes. This is an early horse. And perhaps the most specialised and remarkable of all, at this still very early date, is this extraordinary specimen.

Bat Fossil
Bat Fossil

This, as you can see, is a bat. And the preservation is so remarkable that the skin can be easily seen, not only on its forelegs, which turns them into wings, but even you can see this large ear on the side of its head, which suggests that already it has begun to echo-locate, to hear its own calls so it navigates during flying.

Life after Dinosaurs

The mammals were displaying an extraordinary ability to rapidly adapt their bodies to fill the range of niches left vacant by the death of the dinosaurs.

They had new opportunities but they also faced a new evolutionary pressure. Climate change.

10 million years of gradual global warming had triggered a surge in plant life. The land became covered in forests that grew ever denser and darker. New mammals emerged with new features that helped them to thrive in this changed environment. Features that would have huge significance for humans.

Early Primate
Early Primate
David Attenborough

This is an early member of the group of mammals that was going to produce us. This is an early primate. And you can see that on its front legs, it’s hands, they have an opposable thumb, so it could grasp. And the same on the back legs – the big toe is also opposable. So, this animal was a climber.

The primates could now reach food that was high up in trees. And it’s thought that it was a new type of food that triggered another astonishing advance in their bodies. A major improvement is in sight.

Dr Sandra Engels is part of a team investigating the diet of the fossilised primate from the Messel Pit. Remarkably, she is able to examine the preserved contents of its gut.

Dr Sandra Engels on meteor impact

Sandra Engels “We have particles of the last meal of this primate, and we analysed it with very high magnification and we found the oval outline of a seed which is part of a fruit. Because we found it in the gut of this primate, we know that it fed on fruit.”

Dr Sandra Engels
Dr Sandra Engels

3-D scans of its teeth make it clear that fruit was a major part of its diet. This animal was a specialised fruit-eater.

Sandra Engels “If we take a closer look to the shape of the teeth, we have structures as deep basins or rounder cusps that are at the right tools to break up fruit.”

47 million years ago, large, fleshy fruit like this had only recently been developed by plants. It was one of the ways in which they had adapted to the new dense forest environments.

Colourful Toucan
Colourful Toucan

Many early plants relied on the wind to distribute their seeds. But in the forest, there is little or no wind, so they had a problem. They solved it by recruiting the help of birds, and they did that by wrapping their seeds in an edible, sweet flesh, fruit. Birds carried the seeds in their stomachs and eventually deposited them elsewhere in the forest.

Primates exploit cosy Arrangements

The primates had clearly begun to exploit this cosy arrangement, but to take full advantage of life after the meteor impact, they needed to improve their vision. During the age of the dinosaurs, when the mammals were largely nocturnal, they had developed better night vision, but sacrificed a feature not needed in the dark. The ability to see colour. Today, most mammals still see the world largely in black and white. But the reptiles and their cousins, the birds, retained excellent colour vision. And the fruit-bearing plants had evolved a signalling arrangement to match.

Colour Coded Fruit
Colour-Coded Fruit

There’s no point in having your seeds distributed before they are fully formed. So, the plants evolved a colour-coding system to show when that was. This plant, for example, here is a young fruit still growing. Its flesh is hard and bitter, and it’s green. But this fruit is fully formed. Its flesh is good to eat, soft, and the seed within is ready to go. And it’s red.

To spot a flash of red colour in amongst the green foliage is easy for a bird or a reptile. But for a mammal, with their night-time vision, red and green are indistinguishable. Then, remarkably, some of the primates managed a feat no other mammal has achieved. They put evolution into reverse and re-acquired colour vision.

The common ancestor of this monkey, and of me, lived up in the trees in the daylight. And they quickly evolved the ability to see colour, and therefore, to know which was ripe and which was unripe fruit, and so take advantage of the system that had already been worked out between the birds and the plants.

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