Proteins dating back 23 million years have been isolated from a prehistoric rhinoceros species in the Arctic.
Traces of preserved proteins have been detected in fossils up to 23 million years old an impressive technical achievement that promises to shed light on the evolution, diet, and behavior of species from the distant past.
The analysis of ancient proteins, a field known as paleoproteomics, now joins modern techniques for extracting prehistoric DNA, which in some cases can survive for at least two million years (with the current record held by samples from Greenland’s permanently frozen ground).
Proteins, being slightly more resilient than DNA molecules, have the potential to persist even longer, though the issue remains controversial.
In the 2000s, two teams of paleontologists claimed to have isolated dinosaur proteins dating back 68–80 million years, but their findings were met with strong skepticism. The most widely accepted record until now involved proteins from Arctic camels dating back 3.8 million years.
Proteins From Teeth
Two new studies published in Nature push the boundaries further by examining proteins preserved in tooth enamel the hardest material in the bodies of mammals, which helps protect biomolecules.
The first and more persuasive of the two studies detected proteins in fossils of an extinct rhinoceros species discovered in 1986 on an Arctic island in Canada (pictured) and now housed in a museum in Ottawa. According to earlier research, the fossils are 23 million years old. The cold Canadian climate is believed to have played a major role in preserving the ancient molecules, which break down far more easily at high temperatures.
The second, more controversial study identified traces of proteins from five species of rhinoceros, elephants, and hippopotamuses that lived between 1.5 and 18 million years ago in Turkana, Kenya one of the hottest regions on Earth. Although the researchers report finding chemical alterations that indicate the proteins are ancient, independent experts have expressed caution in interpreting the results.
Proteins are long chains of smaller molecules called amino acids. Because amino acid sequences differ even among closely related species, paleoproteomics can reveal information about where extinct species fit on the tree of life.
“Proteins are encoded by DNA, so protein sequences can reveal details about relatedness between different individuals,” said David Green of Harvard University, lead author of the study on the Kenyan fossils.
In the Arctic rhinoceros study, comparing the ancient sequences with those of modern rhinoceros species showed that the prehistoric species diverged from its living relatives far earlier than previously thought between 25 and 41 million years ago.
Future research examining carbon and nitrogen isotopes in preserved proteins could provide insights into the diet and environment of extinct species. Even an animal’s sex, researchers noted, can be determined from small differences in protein sequences.
And as technology advances, the record for the oldest preserved proteins will eventually be broken again potentially taking us back to the age of the dinosaurs.
