Secrets of rhino evolution found in 20-million-year-old tooth

A fossilized rhino tooth, buried for over 20 million years, is now helping scientists rewrite the history of early rhino evolution.

Inside the tooth enamel, researchers found something remarkable: preserved proteins that held clues to the animal’s lineage and evolutionary split from other species.

This breakthrough came from scientists at the University of York. By analyzing enamel proteins in the tooth, the experts traced key moments in rhino evolution much further back than previously possible.

Reconstructing the rhino family tree

The team discovered that this particular rhino diverged from other members of the family Rhinocerotidae during a window between 41 and 25 million years ago. This coincides with a time between the Middle Eocene and Oligocene Epochs.

Even more surprising was that the data revealed that the two main subfamilies of rhinos – Elasmotheriinae and Rhinocerotinae – split later than previously thought.

Instead of parting ways in the Eocene, as earlier bone studies suggested, this separation likely occurred during the Oligocene, between 34 and 22 million years ago.

This new timeline helps scientists better understand how different rhino species emerged, adapted, and survived (or didn’t) through changing environments.

Rhino evolution revealed in DNA

Ancient DNA has helped researchers study extinct species, but it rarely survives beyond a million years. This fossil tooth changes that.

The successful recovery of enamel proteins from a sample over 20 million years old extends the timeline for molecular research by a factor of ten.

This is important because it allows scientists to explore evolutionary history through molecular evidence – not just fossil shapes. Well-preserved enamel proteins offer access to valuable genetic information, opening new avenues for discovery.

Enamel is the hardest tissue in the body. Its mineral-rich structure protects proteins for millions of years, especially in cold environments where this tooth was found.

Keeping the fossil tooth data pure

The fossil tooth was found in Canada’s High Arctic – a region where permafrost still dominates. That cold environment played a key role in keeping the proteins intact, but cold alone wasn’t enough.

To make sure the proteins were truly ancient, researchers at the University of York ran tests using a method called chiral amino acid analysis.

This technique helped the team distinguish between original proteins from the rhino’s life and any later contamination.

By comparing the degraded proteins in this tooth with those from previously studied rhino fossils, they confirmed the material was genuine.

Unique environmental history of the site

Professor Enrico Cappellini from the University of Copenhagen’s Globe Institute emphasized the significance of the fossil site.

“The Haughton Crater may be a truly special place for palaeontology: a biomolecular vault protecting proteins from decay over vast geological timescales,” said Cappellini.

“Its unique environmental history has created a site with exceptional preservation of ancient biomolecules, akin to how certain sites preserve soft tissues. This finding should encourage more paleontological fieldwork in regions around the world.”

Exploring further back in time

Dr. Marc Dickinson, a postdoctoral researcher at the University of York’s Department of Chemistry, was one of the co-authors on the study.

“It is phenomenal that these tools are enabling us to explore further and further back in time. Building on our knowledge of ancient proteins, we can now start asking fascinating new questions about the evolution of ancient life on our planet,” said Dickinson.

The team sees this fossil tooth as more than just an isolated find. It’s a signal that there may be more ancient biomolecules waiting to be studied.

New perspective on rhino evolution

“Successful analysis of ancient proteins from such an old sample gives a fresh perspective to scientists around the globe who already have incredible fossils in their collections. This important fossil helps us to understand our ancient past,” said Fazeelah Munir, who analyzed the tooth during her doctoral research at York.

Modern rhinos are threatened by habitat loss, poaching, and climate change. Tracing their evolutionary history reveals how past environmental shifts shaped the species we see today.

The more we understand what helped ancient rhinos survive – or led to their decline – the better equipped we are to protect the few that remain.

The full study was published in the journal Nature.

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