Scientists have discovered the oldest surviving proteins in the tooth of a prehistoric rhino known as Elasmotherium, which had a unicorn-like horn. These protein sequences, dating back 20 million years, surpass the previously known oldest sequences from mammoths (1.2 million years old) and camel ancestors (3.7 million years old). Despite the tooth being found in Canada, Elasmotherium was closely related to ancient rhino lineages from Eurasia.
Elasmotherium sibericum, an ancestor of modern rhinos, once roamed the steppes of Eastern Europe and the extreme north of Canada. Covered in shaggy fur similar to its relative, the woolly rhino, Elasmotherium was nicknamed the “Siberian Unicorn” due to its single horn. The discovery of intact protein sequences in the tooth, preserved in the permafrost of the Haughton Crater in Canada’s High Arctic tundra, provides valuable insights into the evolutionary past.
The research team from the University of York uncovered this groundbreaking find, shedding light on ancient genetic material. By extracting proteins and amino acids from the enamel of the tooth, they were able to recover at least seven proteins and 251 amino acids. The results challenged previous assumptions made from morphological studies of rhinocerotid fossils.
This discovery not only expands our understanding of ancient genetic material but also highlights the importance of favorable preservation conditions in polar landscapes, which protect biomolecules from degradation. The study, recently published in the journal Nature, utilized paleotemperature models to analyze the impact of temperature fluctuations on biomolecular preservation over millions of years. By studying the survival of proteins through different epochs, from the Miocene to the Pleistocene, the researchers gained valuable insights into the evolutionary history of Elasmotherium and its relatives.
The analysis of the proteins in the new samples confirmed that they were not contaminants, but indeed belonged to the tooth of an Elasmotherium, distinct from other rhinocerotid specimens. Rhinocerotids underwent a period of diversification before the emergence of this specific creature. They appeared during the Middle to Late Eocene (47.8 to 34 million years ago) and diversified significantly by the Early Oligocene (34 to 32 million years ago). Research on the protein sequences of Elasmotherium indicates that this species diverged from other rhinocerotids around 41-25 million years ago, with the main rhino clades Elasmothieriinae and Rhinocerrotinae separating approximately 34-22 million years ago. Despite its discovery in Canada, Elasmotherium is genetically closer to early rhinos in Eurasia.
The rhinocerotid found in the Haughton Crater exhibits morphological similarities with early-diverging lineages from Eurasia, particularly those in the genus Epiaceratherium. Similarly, some other vertebrates in the unique fauna of the Haughton Formation have their closest relatives in Eurasia.
While there are no immediate plans for Elasmotherium de-extinction, the newfound knowledge about rhino evolution could be valuable in conservation efforts to increase the population numbers of endangered rhinos and prevent their extinction.
