University of York

• But in 2017, while a Ph.D. student of paleobiology at the University of Bristol in the U.K., I heard a gleeful exclamation from across the room.
• The instrument had detected telltale signatures of ancient amino acids in eggshell.
• Amino acids are the building blocks that make up protein sequences in living organisms.

• As Penkman’s enthusiasm suggested, these amino acids were extraordinary.
• In fact, this result came unexpectedly amid our team’s efforts to test claims of near-pristine protein preservation in dinosaur bone.

Orphan fossil fragments

• I predicted that if dinosaur eggshells didn’t preserve any original proteins, then their bones likely wouldn’t preserve any either, and wanted to see whether that was the case.
• Around 2000, many eggshell fragments were illegally exported from Argentina into the commercial market.
• These fossil fragments in some ways gained scientific value because they didn’t belong to any museum collections.

Amino acids in eggshell

• Although some eggshells preserved amino acids far better than others, the evidence overall suggested that these molecules were ancient and original, possibly ranging from 66 million to 86 million years old.
• The remaining amino acids we detected, however, consisted of free molecules that had broken off from their protein chains by reactions with water.

• Amino acids can occur in left- or right-handed configurations.
• After the organism dies, amino acids can convert between handedness until they reach 50-50 mixtures of both configurations.

Calcite, an amino acid archive

• Bird eggshell is even among the best materials to find preserved protein sequences in fossils, let alone free amino acids.
• Demarchi’s team has detected short, intact sequences of amino acids still bound in a chain from bird eggshell at least 6.5 million years old.
• Other researchers have claimed to have found more ancient amino acids, as well as more extreme and less likely claims of preserved protein sequences.

Using calcite to look back in time

• So, what messages from ancient life might persist in these calcite time capsules?
• For example, marine arthropods called trilobites that lived more than half a billion years ago had calcite in their eyes.
• Fossil calcite, Earth’s molecular time capsule, may send faint tales from long-gone life for researchers to better understand their biology.

This research was supported by the University of Bristol Bob Savage Memorial Fund and the Leverhulme Trust (PLP-2012-116).