In New "Game-Changer", Scientists Extract 24-Million-Year-Old Protein Fragments From Extinct Rhino Tooth

Scientists have got their hands on the oldest animal proteins yet, extracted from 18-million-year-old fossilized mammal teeth in East Africa, pushing the record back by an astonishing 14 to 15 million years. Even older partial fragments of proteins were obtained in North America from a rhino tooth dating up to 24 million years old, offering an unprecedented glimpse into life deep in the ancient past.

"This discovery is a game-changer for how we can study ancient life," Ryan Sinclair Paterson, lead author of one of the studies and a postdoctoral researcher at the Globe Institute at the University of Copenhagen, said in a statement seen by IFLScience.  

Information held within ancient molecules, like protein and DNA, can be pieced together to help understand how ancients (including humans) lived thousands, if not millions, of years ago. The only problem is that these molecules degrade over time, especially in warm environments. 

However, in two new studies published today, scientists show that it’s possible to recover and analyze proteins that are far older than previously believed. It’s all thanks to dental enamel, the toughest substance in the vertebrate body, that’s able to provide an exceptionally stable shelter from the outside world that can protect ancient proteins from degradation for millions of years.

In one study, researchers at the Smithsonian’s Museum Conservation Institute and Harvard University analyzed fossils from Kenya’s sweltering Turkana Basin, home to some of the richest records of Cenozoic mammal evolution. They recovered protein fragments from the enamel of extinct rhinoceros species and long-gone elephant ancestors that are up to 18 million years old.

Despite the harsh conditions of East Africa, the youngest samples still held a surprising number of intact peptides, offering a reliable protein record across a third of the Cenozoic Era.

“The ability to use proteins to study ancient life in the Cenozoic has generally been limited to the last few million years,” noted Timothy Cleland, a physical scientist at the Museum Conservation Institute and the senior investigator on this study. 

“The natural degradation of proteins severely limits our ability to gain a full understanding of how these animals lived and evolved. Our findings, however, reveal that protein trapped within dense enamel can persist longer, even in tropical environments where temperature accelerates protein loss, and can reveal details about life much farther back in the fossil record.”

In another study, scientists led by the University of Copenhagen managed to successfully extract and sequence bits of ancient enamel proteins from a fossilized rhino tooth found in Canada's High Arctic, dating to 21-24 million years ago. 

These were only fragments of proteins – partial sequences of seven different enamel proteins and over 1,000 short chains of amino acids – but they were enough to divulge useful information about the animal’s evolution. 

"We've effectively opened a new chapter in molecular palaeontology. Imagine being able to use molecular data to understand organisms that lived tens of millions of years ago, long before the earliest evidence of ancient DNA," added Enrico Cappellini, senior author and molecular biologist at the University of Copenhagen. 

These two studies crack open a new window into the deep past. Until now, ancient proteins detailed enough to shed light on evolutionary relationships had only been recovered from fossils dating back around 4 million years, but this new work stretches that limit by a massive extent. 

It suggests that, under the right conditions, proteins can outlast DNA by tens of millions of years, preserving biological clues from long-extinct species. It also holds the potential to illuminate the story of our own species by revealing hidden chapters from the lives of our ancient relatives.

“Ancient DNA has produced a revolution in our understanding of recent human origins,” said Daniel Green, field program director at Harvard University and the first study’s lead author. “We hope that paleoproteomics may lead to a similar revolution in the study of evolutionary processes that occurred many millions of years earlier.” 

The two new studies are published in the journal Nature, accessible here and here.