Palaeoproteomics is the study of ancient proteins preserved in fossils. Because proteins survive far longer than ancient DNA (aDNA), which lasts about 1m years, the field extends the molecular study of extinct species by roughly ten-fold.
Two studies published in Nature on July 9th 2025 dramatically extended the timeline of reliable protein recovery. A team from Harvard University and the Smithsonian Institution extracted proteins from the tooth enamel of large African animals in Kenya's Turkana Basin, dating from 1.5m to as much as 29m years old (with high confidence up to 18m years). The fact that proteins survived in one of the warmest places on Earth, where biological molecules easily break down, suggested that even older proteins could be found in cooler climates.
A separate team from the University of Copenhagen confirmed this. In the Haughton Crater in the Canadian Arctic, they extracted protein sequences from the tooth of a 24m-year-old rhinocerotid, a squat, single-horned mammal in the rhinoceros family.
Both teams recovered proteins from tooth enamel, the hardest substance in vertebrates' bodies. They ground the enamel to a powder and applied a chemical solution to draw out the proteins. To confirm the proteins were genuine and not modern contamination, they identified chemical damage accrued over time through a process called diagenesis.
Comparing recovered protein sequences against databases of known proteins allows scientists to place extinct species on the tree of life. The Harvard study, for instance, suggests that an 18m-year-old creature in the Anthracotheriidae family is probably the ancestor of modern hippos, whereas the close relatives of a rhino-like animal called Arsinoitherium, thought to be 29m years old, are all extinct.
Future analyses of carbon and nitrogen isotopes within preserved proteins could offer insights into the diet, environment and migratory behaviour of extinct species. Because some proteins in tooth enamel vary between the sexes, they could also help determine the sex of fossils, which can otherwise be tricky.
In 2009 researchers from North Carolina State University retrieved fragments of collagen protein from an 80m-year-old duck-billed dinosaur called Brachylophosaurus canadensis. Although degraded into small bits, the collagen was confirmed to be of a specific kind now found only in birds. Better-preserved proteins yet to be found might reveal even more about deep evolutionary history.
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