Ancient Tooth Enamel Reveals Evolutionary Secrets
In a groundbreaking discovery, scientists have extracted and sequenced proteins from tooth enamel up to 24 million years old, potentially revolutionizing our understanding of evolutionary relationships among extinct species.
Untangling Evolutionary Trees
Traditionally, paleontologists have relied on the morphology of fossilized bones to construct evolutionary trees, a method which can often be ambiguous. While DNA analysis offers more precise data, its fragile nature limits its use to specimens younger than approximately 1.2 million years. However, proteins found in dental enamel offer a more durable alternative.
This is all very exciting stuff,”
says paleontologist Evan Saitta from the Field Museum of Natural History, who was not involved in the research.
Ryan Paterson, a biomolecular paleontologist at the University of Copenhagen, believed that enamel, the hardest tissue in the body, could protect proteins for extended periods. Paterson’s team focused on the Arctic, where cold temperatures could further aid preservation.
Arctic Rhino Discovery
Analyzing a 22-million-year-old tooth fragment from an ancient rhino relative unearthed in the Canadian Arctic, Paterson‘s team successfully identified approximately 1,000 peptides. This allowed them to place the specimen within its family tree, and the protein data suggests that a crucial divergence in the rhino lineage occurred more recently than previously estimated.
Kenyan Fossils Offer Insights
In a separate study, researchers examined ten fossil teeth, with ages ranging from 1.5 to 29 million years, discovered in Kenya’s Turkana Basin. Despite the harsh climate, the team managed to extract peptides from an 18-million-year-old rhino relative and 16-million-year-old teeth belonging to three proboscidean species (ancient elephant relatives).
There’s an enormous amount of controversy among paleontologists about what the evolutionary relationships are between these different proboscidean taxa,
explains Daniel Green, a paleontologist at Harvard University and coauthor of the paper.
These findings could help resolve long-standing debates surrounding the evolutionary history of elephants, according to Green. Today, the African bush elephant, African forest elephant and Asian elephant are the only remaining proboscidean species, with populations totaling roughly 400,000, 40,000 and 50,000 respectively (WWF).
The Chemistry of Preservation
Enamel proteins are closely associated with hydroxyapatite, a biomineral. I’m actually not surprised that you can get proteins preserved on mineral surfaces,
says Karina Sand, a biogeochemist at the University of Copenhagen.
However, the advanced age of these proteins remains surprising, says Sand. The findings open new possibilities for understanding the complex interactions between minerals and proteins in fossil preservation.
Methodological Differences
Maarten Dhaenens, a proteomics expert at Ghent University, notes that the methodology used in the Arctic rhino study is well-established and convincing. However, he suggests that the methods employed in the Turkana Basin research may require further validation.
Future Research
While cold environments favor protein preservation, Saitta suggests that the discovery of million-year-old proteins near the equator implies that similar finds are possible in other environments worldwide.
These discoveries mark a significant advancement in the field of paleoproteomics, providing a new tool for deciphering evolutionary relationships and expanding our knowledge of ancient life.
