Paleontology has just taken a major step with the discovery of intact proteins in fossils dating from Miocene.
This advance, published in Nature, are based on the analysis of fossilized rhinos from two opposite sites: the Canadian Arctic and the Arid Basin du Turkana, in Kenya. The researchers identified old protein sequences from 18 to 24 million years old, far beyond previous records.
Image: University of York
Dental enamel, a molecular safe
The enamel of the teeth turned out to be an exceptional support for protein preservation. Its rigid mineral structure protects the organic molecules from degradation, even in hostile environments. In Kenya, high temperatures did not prevent their preservation. The extracted proteins made it possible to reconstruct evolutionary links between missing species and their modern descendants. For example, an Arctic Rhinoceros turned out to belong to a distinct line, questioning certain previous classifications.
These discoveries confirm that proteins are much more resistant than DNA, the latter surviving difficult to a million years. They open the way to the study of ancient species whose genetic material was so far considered to be lost.
New connections in evolutionary history
The analyzes have highlighted unsuspected evolutionary differences. The Arctic Rhinoceros, for example, would have separated from other species 41 to 25 million years ago, much earlier than morphological studies suggested.
Researchers are now planning to apply these methods to other groups, such as the first hominids. Proteins could illuminate mysteries such as the origin of hippopotams or the evolution of mammals after the extinction of dinosaurs.
These works also show that various environments, from polar cold to scorching deserts, can preserve biomolecules. This diversity considerably extends the areas conducive to future discoveries.
