An international research team led by Curtin University has used prehistoric faeces to better understand how molecular fossilisation works, offering a new window into what ancient animals ate, the world they lived in and what happened after they died.
Published in the journal Geobiology and funded by the ARC Laureate Fellowship program, the study examined 300-million-year-old fossilised droppings, or 'coprolites', mostly from the Mazon Creek fossil site in the United States.
The coprolites were already known to contain cholesterol derivatives, which is strong evidence of a meat-based diet, but the new research explored how those delicate molecular traces were preserved and survived the ravages of time.
Usually, soft tissues are fossilised due to phosphate minerals, but the study found molecules were preserved thanks to tiny grains of iron carbonate scattered throughout the fossil, acting like microscopic time capsules.
Study lead Dr Madison Tripp, an Adjunct Research Fellow at Curtin's School of Earth and Planetary Sciences, said the findings add a new dimension to how scientists understand molecular preservation, which is crucial to gaining insights into the ancient world.
"Fossils don't just preserve the shapes of long-extinct creatures - they can also hold chemical traces of life," Dr Tripp said.
"But how those delicate molecules survive for hundreds of millions of years has long been a mystery: since phosphate minerals help preserve the fossil's shape and structure, we might have expected these to also help preserve molecules – but we found instead that it was the iron carbonate that shielded the molecular traces inside.
"It's a bit like discovering a treasure chest - in this instance phosphate - but the real gold is stashed in the pebbles nearby."
To determine whether this mineral/molecule association was unique to the Mazon Creek site, researchers expanded the analysis to include a diverse range of fossils spanning different species, environments and time periods.
Founding Director of Curtin's WA-Organic and Isotope Geochemistry Centre and ARC Laureate Fellow Professor Kliti Grice said this revealed the findings were consistent across the samples.
"This isn't just a one-off or a lucky find: it's a pattern we are starting to see repeated, which tells us carbonate minerals have been quietly preserving biological information throughout Earth's history," Professor Grice said.
"Understanding which minerals are most likely to preserve ancient biomolecules means we can be far more targeted in our fossil searches.
"Rather than relying on chance, we can look for specific conditions that give us the best shot at uncovering molecular clues about ancient life."
Professor Grice said by revealing how biomolecules are preserved, scientists were gaining powerful new tools to reconstruct the world hundreds of millions of years ago.
"This helps us build a much richer picture of past ecosystems - not just what animals looked like, but how they lived, interacted, and decomposed," Professor Grice said.
"It brings prehistoric worlds to life in molecular detail."
Mineralization controls informative biomarker preservation associated with soft part fossilization in deep time was published in Geobiology.
