Ancient ostrich eggs have helped scientists discover a way to get a glimpse into the distant past of animals and humans, far deeper than any DNA record ever has.
A team of researchers from the Universities of York, Sheffield, and Copenhagen has identified fossil proteins on ostrich eggshells dating as far back as 3.8 million years ago, meaning they could provide genetic information almost 50 times older than any DNA record.
The oldest of the eggshells was discovered in the searing sands of Laetoli in Tanzania. It was previously assumed that proteins and other minerals would be damaged over time, particularly by the high temperatures of the African climate. However, this new study, published in eLife, has found that proteins can be preserved for millions upon millions of years, if they become chemically bound to certain solid mineral surfaces, such as the eggshell.
“Evidence suggested that it was the more fluid, unstable region of the protein that promoted and regulated mineral growth in the shell, but it was also less likely to survive over time and the intense heat of the African climate," Dr Beatrice Demarchi, from the University of York’s Department of Archaeology, said in a statement.
“As we examined older and older eggshells, we could see that this assumption was surprisingly wrong, as it was in fact the unstable regions that survived the best. They were able to bind more strongly to the eggshell, allowing it be preserved in time.”
Wonderwerk Cave, one of the excavation sites where a protein-laden eggshell was found. Michael Chazan, University of Toronto
Now aware of this knowledge, the researchers have been able to extract complete protein sequences from 24 other shells collected across Tanzania and South Africa. Previously, only short sequences of proteins – or their single building blocks, amino acids – have been found to be preserved in older fossils. Since the whole protein sequence can now be identified, scientists will be able to detail the function and story of the protein. It's still early days for research, but this can be used to shed light onto the distant evolutionary history of a species.
What's more, ostrich eggs are also a relatively common find for paleontologists and archaeologists. They can be found at many excavation sites around Africa because early modern humans frequently used them to make art, jewelry, and to carry water.
“Remarkably, in the oldest eggshell in the study – from the famous 3.8-million-year-old site of Laetoli in Tanzania – a region of the protein was still there, giving us a unique insight into what to look for when analysing fossils of this kind,” explained Dr Colin Freeman, from the University of Sheffield.
“Now that we know minerals can trap and preserve proteins in this way, we can be much more targeted in our study of ancient remains.”