Today, in collaboration with PhD student Jochen Brocks and Dr Roger Buick of University of Sydney, AGSO released details of a discovery of a variety of molecular fossils from various groups of organisms in rocks that are 2.7 billion years old. These rocks, from West Australia s ancient Pilbara Craton, contain not only evidence for cyanobacteria, indicating that oxygenic photosynthesis is at least 2.7 billion years old, but significantly evidence for eukaryotic life. The finding is significant because eukaryotes are the group of organisms from which all multicellular life is descended. The organisms detected in this work may have been the ancestors of all modern day plants and animals. The finding of a diverse collection of steranes, similar to distributions found in younger oils and sediments is strong evidence for the existence of eukaryotic biochemistry and is more than one billion years older than previous molecular fossil evidence for this group of organisms.
Molecular fossils are organic compounds that can be related to biochemicals found in living cells.
For example, the remains of cholesterol can be found in oils and sediments as a molecular fossil called cholestane. At AGSO, the study of molecular fossils is used to understand the origins of oil and the organisms that contribute to its formation. The work is carried out on using a technique called gas chromatography- mass spectrometry which is used to help separate and characterise the complex mixture of compounds that are found in oils and sediments. The age and preservation of these molecular fossil is remarkable and rigorous procedures have been developed by Jochen Brocks to assess whether these compounds are really of ancient origin or contaminants introduced at a later date. Rocks of high organic content were compared to adjacent rocks of low organic content to discover if they had underdone contamination by a younger oil moving through the sediments.