"Scientists have found preserved proteins in 3.8-million-year-old ostrich eggshells from Africa.
The researchers say these biological building blocks - bound into the eggshell - could provide genetic information up to 50 times older than any DNA.
These proteins, the team said, had been protected because they had been "entrapped" in surface minerals." (Article continues.)
This is the paper in question:https://elifesciences.org/content/5/e17092
'Protein sequences bound to mineral surfaces persist into deep time.'