Researchers have made a major breakthrough in understanding rhino evolution by analyzing proteins extracted from a fossilized tooth that is more than 20 million years old. By examining these ancient protein sequences, scientists found that this prehistoric rhinoceros separated from other members of the rhinoceros family during the middle Eocene to Oligocene epoch (roughly 41 million to 25 million years ago).
The discovery also provides new insights into when the two main branches of the rhino family - Elasmotheriinae and Rhinocerotinae - separated. Evidence suggests that they diverged later during the Oligocene Epoch (about 34 million to 22 million years ago) than previous fossil-based research suggested.
The successful recovery and analysis of enamel proteins marks a major leap forward in molecular paleontology, extending the known limits of evolutionary protein preservation to a time frame ten times older than the oldest DNA recovered to date.
A team from the University of York was involved in confirming that these proteins and amino acids are indeed of ancient origin. Using a technique called chiral amino acid analysis, they analyzed the rhino tooth, which was unearthed in the Canadian High Arctic, to get a clearer picture of how the proteins within it were preserved.
By measuring the extent of protein degradation and comparing it to previously analyzed rhino material, they were able to confirm that the amino acids were from the teeth themselves and not the result of later contamination.
Ancient rhinoceros teeth. Image source: York University
Dr. Mark Dickinson, co-author and postdoctoral researcher in the Department of Chemistry at the University of York, said: "It's amazing how these tools allow us to explore farther and farther into the past. Building on our knowledge of ancient proteins, we can now start to ask some fascinating new questions about the evolution of ancient life on Earth."
The rhinoceros is of particular interest because it is now listed as an endangered species, so understanding its long-term evolutionary history can give us insights into how past environmental changes and extinctions have shaped the diversity we see today.
Until now, scientists have relied on the shape and structure of fossils or, more recently, ancient DNA (aDNA) to piece together the evolutionary history of long-extinct species. However, aDNA rarely survives for more than 1 million years, limiting its use in understanding deep evolutionary history.
Although ancient proteins have been found in fossils from the Middle to Late Miocene epoch (approximately the past 10 million years), previous access to sequences that were detailed enough to allow for robust reconstruction of evolutionary relationships was limited to samples no older than 4 million years old.
The new study, published in the journal Nature, significantly expands this window, demonstrating that proteins can persist over long geological timescales under the right conditions.
Fazeelah Munir analyzed the tooth while conducting her doctoral research in the Department of Chemistry at the University of York. She said: "The successful analysis of ancient proteins in such ancient samples provides a new perspective for scientists around the world who have collected such precious fossils. This important fossil helps us understand ancient times."
The fossil is located in an area of Canada currently characterized by permafrost, and researchers say the enamel and the relatively cold environment in which the fossil was found played an important role in the long-term preservation of the protein.
Tooth enamel provides a stable "scaffold" that protects ancient proteins from erosion over geological time. Tooth enamel's hardness comes from its complex mineral structure, which acts as a protective barrier and slows the breakdown of proteins after death.
Professor Enrico Cappellini from the Institute of Earth Research at the University of Copenhagen said: "Horton Crater could be a truly special place for paleontology: it is a reservoir of biomolecules that protect proteins from decay over long geological timescales.
"Its unique environmental history has resulted in such well-preserved ancient biomolecular sites, preserved in a manner similar to the way some sites preserve soft tissue. This discovery should encourage more paleontological fieldwork around the world."
Ryan Sinclair-Patterson, a postdoctoral researcher at the Earth Institute at the University of Copenhagen, added: "This discovery will revolutionize the way we study ancient life."
Compiled from /scitechdaily