The world of paleontology is often hampered by a significant hurdle – the scarcity of preserved organic material from prehistoric times. Unlike their modern counterparts, dinosaur proteins and DNA rarely survive the relentless march of millions of years. However, a serendipitous discovery in 2017 challenged this notion and opened a new window into the molecular world of dinosaurs.
Our story begins in the laboratory of Dr. Kirsty Penkman, a renowned scientist specializing in the study of ancient proteins. At the University of Bristol, Ph.D. student Nizar Ibrahim was collaborating with Penkman to investigate claims of preserved proteins in dinosaur bones. Their initial tests yielded a disheartening outcome – no original amino acids, the building blocks of proteins, were found within the fossils. Instead, they were contaminated by microbes from the environments where the bones were buried.
Refusing to be discouraged, Ibrahim, inspired by recent research on bird eggshells, proposed testing dinosaur eggshells instead. This wasn’t part of the original research plan, but fortunately, they had access to some rather unusual fossil fragments. These eggshell pieces originated from Argentina and had been illegally exported into the commercial fossil market. While the ethical implications of the trade are concerning, these fragments presented a unique opportunity for analysis as they weren’t part of any museum collection and could be freely studied.
To their utter surprise, the analysis revealed the presence of telltale signatures of ancient amino acids within the eggshells. Further investigation, involving a larger international team of researchers, confirmed these initial findings. Dinosaur eggshells from Argentina, Spain, and China all bore traces of amino acids, estimated to be between 66 and 86 million years old.
The preserved amino acids weren’t intact protein chains, but rather free molecules that had broken down over eons. Additionally, they were racemic, a state where the left-handed and right-handed configurations of the molecules were present in equal amounts. This indicated a long separation from their original protein structures.
The key to this preservation lies in the eggshell’s composition. Unlike bones made primarily of calcium phosphate, eggshells are composed of calcite, a form of calcium carbonate. This calcite acts as a closed system, trapping the breakdown products of proteins involved in shell formation, including free amino acids. This ‘molecular archive’ allowed the amino acids to survive for millions of years.
While these amino acids might not offer the complete genetic picture that DNA can provide, they still hold immense value. Researchers can analyze the stable isotope ratios of carbon, oxygen, or nitrogen within these amino acids to gain insights into the dinosaur’s diet. These ratios are more likely to reflect the dinosaur’s biology than outside contaminants because the calcite system is relatively closed.
This discovery unlocks new avenues for further exploration. Fossil calcite from other organisms, like the shells of ancient marine arthropods, might hold similar treasures. By studying these ‘molecular time capsules,’ scientists can potentially reconstruct faint echoes of past life, unraveling the biological mysteries of creatures long vanished from our planet.
The initial eggshell fragments, once orphaned and lost in the commercial trade, ultimately found a rightful home – repatriated to Argentina’s prestigious Museo Provincial Patagonico de Ciencias Naturales. This unexpected discovery not only highlights the importance of responsible fossil collection but also serves as a testament to the power of scientific curiosity and collaboration. It reminds us that even the most unassuming objects can hold hidden stories waiting to be unearthed.
Source: The Conversation