Scientists have recovered ancient proteins from a fossilized rhinoceros tooth, breaking new ground in the study of ancient life on Earth. The 24-million-year-old tooth, which was unearthed in the Canadian Arctic, contains proteins that are 10 times older than the most ancient known DNA. Using the sample, scientists have now analyzed the oldest detailed protein sequence on record. "Enamel is so hard it protects these proteins over deep time (long time scales)," said Ryan Sinclair Paterson, a postdoctoral researcher at the Globe Institute at the University of Copenhagen in Denmark who led the Canadian research. "It's essentially like a vault. What we did was unlock this vault, at least for this specific fossil." The study of ancient DNA preserved in bones, fossils and dirt has revolutionized archaeological science, pulling back the curtain on lost empires, mysterious clans, ice age creatures and previously unknown human species. Ancient proteins promise a similar revolution for fossils that are many millions of years old and currently beyond the chronological reach of ancient DNA. The study, which published July 9 in the scientific journal Nature, showcases the enormous potential of the field, known as paleoproteomics. Proteins, which are made up of sequences of amino acids, are more robust than DNA, a fragile molecule that degrades relatively easily. Although proteins contain less detailed information, they can help to elucidate a specimen's evolutionary history, diet, even in some cases the sex of a fossil. "The next step is to demonstrate that it's not just one sample, one lucky strike," said coauthor Enrico Cappellini, a professor at the University of Copenhagen's Globe Institute who has pioneered methods to extricate proteins from fossils and was involved in the Canadian research. "But potentially there's a huge area of research that could be further clarified and then, if we really push it farther ... we could even start to investigate dinosaurs," he added. Cappellini and Paterson, along with colleagues at the University of York and the Canadian Museum of Nature, recovered sequences from seven proteins preserved inside the fossilized rhino tooth. Sequencing ancient proteins involves determining the order of amino acids in a sample. By comparing the sequences with those of living and extinct relatives, the scientists were able to glean information about the evolution of the rhino. The analysis revealed that it diverged from the same family as living rhinos about 41 million to 25 million years ago. "In the fossil record, there were some crazy forms (of rhinoceros species). There's the woolly rhinoceros, and maybe you've heard of the Siberian unicorn with the gigantic horn," Paterson said. "What we were able to do is compare our mystery rhino with other forms and find out where it falls in the family tree." Separate research, also published July 9 in the journal Nature, which sampled fossils from Kenya's Turkana Basin, suggests that biomolecules can survive for millions of years, even in searing, tropical environments. The study, which analyzed 10 mammal fossils, including the relatives of today's elephants, hippos and rhinos, was published by researchers at the Smithsonian Institution's Museum Conservation Institute and Harvard University. They recovered proteins from five of the fossils dated 1.5 million to 18 million years ago, and found that even in tropical regions with high temperatures scientists can extract prehistoric proteins, which can reveal links between ancient elephants and rhinos and their modern-day relatives. While the information contained in the Kenyan proteins wasn't as detailed as that found in the Canadian fossil, the authors said that their presence within enamel tissues in one of the world's warmest regions holds promise that proteins in much older fossils could be discovered. "We were excitingly successful. We went back to about 18 million years. I think going back in time should be possible," said study author Timothy Cleland, a physical scientist at the Museum Conservation Institute. The research on the Canadian fossil was "sound and super interesting," said Maarten Dhaenens, a researcher at the University of Ghent in Belgium who specializes in proteomics. However, Dhaenens, who wasn't involved in either study, said the methodology used on the Kenyan fossils was complex and less tested. The researchers' findings, he argued, are harder to interpret and warranted a more thorough assessment. "The data is publicly available, so we should be able to verify their claims through manual validation, but this takes time," he said via email. Evan Saitta, paleontologist and research associate at Chicago's Field Museum of Natural History, said it was "shocking" to find proteins preserved within fossils at tropical latitudes and added that the findings needed replication. It had been previously assumed that cold temperatures were necessary to slow down the breakdown of proteins. "If that is a true result ... it should be very easy to replicate," he noted. "We should be able to go around all different fossil sites all over the world and find enamel peptides (proteins)." Getting proteins from fossils this old would be a palaeontologist's dream come true, said Matthew Collins, the McDonald Professor in Palaeoproteomics at the UK's University of Cambridge, who agreed that the research on the Canadian fossil was more convincing. Collins, like Saitta, was not involved in the new research. "This is amazing. It's really exciting, but at the same time I've been disappointed so much in my career by thinking that we had very old proteins and we didn't," added Collins, who has tried to recover proteins from dinosaur fossils. Collins and Saitta were part of a team that detected amino acids in a titanosaur eggshell fragment, according to research published in 2024. The egg was laid by a plant-eating sauropod, a huge, long-necked dinosaur that lived in the Late Cretaceous, shortly before dinosaurs went extinct 66 million years ago. However, the dinosaur eggshell lacked any identifiable protein sequences. Their results were akin to identifying five letters in a novel, revealing only a pattern of decay that showed there were once proteins in the eggshell, said Saitta. "There's no sequence left, no information, just the little individual Lego building blocks of (amino acids)," Collins said. Getting protein information from a dinosaur tooth is a long shot, and Saitta noted that he had given up looking for proteins in dinosaur fossils in favor of exploring more interesting research questions. Not only are dinosaur fossils far older than the fossils in the two studies, he noted, but they mostly date back to a hothouse period in the global climate when there were no ice caps. What's more, on average, dinosaur fossils are buried far deeper and thus have experienced far greater geothermal heat. It's also not clear whether dinosaur teeth had thick enough enamel to preserve proteins, he added. Cappellini and Paterson said it might be possible to retrieve useful protein information from dinosaur fossils within 10 years, although there were other interesting questions to investigate first, such as how mammals came to dominate the planet after the dinosaurs' demise. "I really think some sites might preserve dinosaur proteins in deep time. Maybe we can give those a shot," Paterson said. — CNN
