For centuries, fossils have been humanity’s window into the deep past, preserving the shapes of creatures that roamed the Earth millions of years ago. Bones, shells, and imprints in stone tell us about their size, structure, and movement. But what if fossils could tell us more—not just what ancient animals looked like, but what they ate, how they lived, and even the microscopic chemistry of their bodies? An international research team led by Curtin University has now shown that they can, thanks to the remarkable preservation of molecular traces in prehistoric feces.
Published in Geobiology, the study focused on fossilized droppings, or coprolites, that are around 300 million years old, primarily from the Mazon Creek fossil site in the United States. While scientists already knew these coprolites contained cholesterol derivatives—a chemical signature pointing to a meat-based diet—the new research went further. It revealed how these delicate molecular traces survived the ravages of deep time, offering a new window into both the diets of ancient animals and the environmental conditions that helped preserve them.
Molecular Fossils: More Than Just Shapes
Traditionally, fossilization has been understood as a process of hard tissues being preserved through minerals like phosphate. Bones and shells maintain their structure as minerals infiltrate and replace organic material, creating stone-like replicas of once-living organisms. But soft tissues and fragile molecules are far harder to preserve, often decaying long before they can be fossilized. The mystery of how molecular traces survive millions of years has long challenged scientists.
Dr. Madison Tripp, lead author of the study and Adjunct Research Fellow at Curtin’s School of Earth and Planetary Sciences, describes the discovery with a vivid metaphor. “Fossils don’t just preserve the shapes of long-extinct creatures—they can also hold chemical traces of life,” she said. “But how those delicate molecules survive for hundreds of millions of years has long been a mystery. We might have expected phosphate minerals, which help preserve the fossil’s shape, to also protect molecules—but we found instead that it was the iron carbonate grains scattered throughout the fossil that acted like microscopic time capsules.”
In essence, the phosphate minerals are like a treasure chest holding the structure of the fossil, but the iron carbonate grains are where the real “gold”—the molecular clues—are hidden. These tiny mineral grains shield delicate molecules, preserving them intact over vast stretches of geological time.
Beyond Mazon Creek: A Universal Pattern
To determine whether this phenomenon was unique to the Mazon Creek site, the researchers expanded their analysis to include fossils from a wide range of species, environments, and eras. The findings were consistent: carbonate minerals were consistently associated with the preservation of molecular traces.
Professor Kliti Grice, Founding Director of Curtin’s WA-Organic and Isotope Geochemistry Center and an ARC Laureate Fellow, emphasized the significance of this discovery. “This isn’t just a one-off or a lucky find,” she said. “It’s a pattern that is emerging across Earth’s history. Carbonate minerals have quietly been preserving biological information for hundreds of millions of years.”
This insight has profound implications for paleontology. Instead of relying on chance to stumble upon fossils that might contain molecular information, scientists can now target specific conditions where carbonate minerals are present, dramatically improving the likelihood of uncovering molecular clues about ancient life.
Reconstructing Prehistoric Worlds in Molecular Detail
The preservation of biomolecules opens up a new realm of possibilities for understanding the past. Fossils have always allowed us to visualize ancient life, but molecular fossils go further: they let us reconstruct ecosystems at the chemical level. We can infer diets, metabolic processes, and even interactions between species. Soft tissues, once considered almost impossible to study after millions of years, now offer a molecular glimpse into how ancient creatures lived, ate, and decomposed.
Professor Grice explains the transformative potential of these discoveries: “Understanding which minerals preserve biomolecules allows us to reconstruct past ecosystems in unprecedented detail. It’s not just about knowing what animals looked like—it’s about seeing how they lived, how they interacted, and how the natural world responded to their presence. It brings prehistoric worlds to life at a molecular level.”
A New Era in Fossil Research
This research underscores a broader revolution in paleontology and geochemistry. By revealing the mechanisms of molecular preservation, scientists can now explore questions previously thought inaccessible. What did ancient diets look like in different regions? How did environmental changes influence the chemistry of decay and preservation? Could we one day reconstruct entire ancient food webs from the chemical signatures locked inside fossils?
These questions are no longer just speculative. Molecular fossils, preserved by the quiet protection of carbonate grains, are unlocking answers. Each coprolite, each trace molecule, is a fragment of a story that stretches back hundreds of millions of years, waiting for scientists to read it.
Conclusion: Treasures in Ancient Droppings
It may seem unglamorous, even humorous, to imagine unlocking the secrets of the past from fossilized feces. Yet these prehistoric droppings are proving to be some of the richest sources of information about ancient life. They reveal diets, preserve molecules that survive the ages, and provide new tools for reconstructing ecosystems that no longer exist.
Through the combined efforts of geochemists, paleontologists, and chemists, the ancient world is revealing itself in ways never imagined. Iron carbonate grains, scattered like tiny guardians throughout fossils, have been silently safeguarding the molecular treasures of the past. What once seemed mundane—animal droppings—now serves as a profound key to understanding life hundreds of millions of years ago. In these humble coprolites, scientists are discovering that the story of life, death, and preservation is far richer, more intricate, and more astonishing than anyone could have guessed.
The past is speaking, in molecules and minerals alike, and we are finally learning to listen.
More information: Mineralization Controls Informative Biomarker Preservation Associated With Soft Part Fossilization in Deep Time. Geobiology. DOI: 10.1111/gbi.70030. onlinelibrary.wiley.com/doi/10.1111/gbi.70030
