Rat-like creature is our oldest ancestor

The naming of the shrew: One of the new species was named Durlstotherium newmani after a local pub landlord.

Does it matter what species we are descended from? Experts have identified what they believe to be our oldest ancestors: shrews. Much has changed in the 145 million years since they lived.

What’s happening

Fossilised teeth found in Dorset belong to humans’ oldest known ancestors, scientists say. The teeth, which are 145 million years old, came from two “rat-like things” or shrews which lived alongside dinosaurs. They were discovered by a student and identified by palaeontologists at his university.

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“My jaw dropped,” says one researcher of the moment he saw the fossils. He knew that they were something special: evidence of a very old species of eutherian mammal, dating from the Early Cretaceous period. The eutherian group has evolved to include whales, mice and — yep — Homo sapiens.

What unites these species? We all have a placenta, and we share certain bone and tooth features (hence why the researchers could identify this species). But we may have more in common than that. A new study suggests that all mammals were once night creatures, and some only switched to day after the dinosaurs died out. This could explain why many mammals today are nocturnal.

The fact that we are descended from shrews seems odd. What can we take away from it?

Some say…

This discovery is cool, but I feel no connection to the shrews. So much evolution has happened in 145 million years that we might as well be unrelated. If we really want to learn about humanity, we need to study ourselves as we are today. That is what fields like sociology and medicine do. Staring at teeth in bits of rock gets boring fast.

Others think…

We can learn a lot by comparing ourselves with our ancestors. We find out which biological features survived and which were phased out. This helps us see how we have adapted to our environment, and what makes us so powerful. At the same time, it reminds us that we were not always as we are now, and that we will continue to change. That is humbling.

You Decide

  1. Should we all study fossils at school?

Activities

  1. In groups of three, try to imagine what humans (or our descendants) will be like in 145 million years’ time. You can use drawings to illustrate your ideas.

Some People Say...

“Humans are a unique species.”

What do you think?

Word Watch

Dorset
The discovery was made on the Jurassic Coast, known for its fossils (found in rock).
Palaeontologists
Scientists who study fossils.
Eutherian
Almost all mammals existing today belong to this group.
Homo sapiens
Latin for wise man. The primate species of human beings (that’s us). Primate means an order of mammals (including monkeys and humans) with hands, hand-like feet and forward-facing eyes.
Placenta
An organ next to the foetus (baby) in the womb, transferring oxygen, nutrients and waste between it and the mother.
Nocturnal
Done at night. Describes animals active at night, such as bats.
Sociology
The study of society (how people live together).

Subjects

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