The contamination in the rock samples was found by a Curtin
University team (pictured).
Professor Birger Rasmussen and Dr Ian Fletcher have helped rewrite the early history of life in the latest edition of Nature.
The Curtin researchers found that biomarkers contained in 2.7 billion year old rocks, which had previously provided evidence of the earliest known oxygen producing bacteria and organisms, were probably contaminated.
Their paper "Reassessing the first appearance of eukaryotes and cyanobateria" was published in the prestigious international science journal on Thursday 23 October 2008.
Detailed analysis by the Curtin-led team using a NanoSIMS ion microprobe has indicated that the biomarkers probably represent contaminants, presumably introduced from younger sedimentary rocks, or during drilling or sample handling.
Professor Rasmussen said the results have changed the map of early life and puts to rest previous scientific concerns.
'In the absence of the biomarker evidence, the oldest unambiguous fossil evidence for cyanobacteria is only about 2.2 billion years old, while the oldest probable eukaryotic fossils are about 1.7 billion years old, both significantly younger than the 2.7 billion year age proposed previously.'
'We now have an answer to the long apparent delay between the first chemical evidence for eukaryotes and oxygen-producing cyanobacteria, and the first geological record of these events.'
The group now plans to use NanoSIMS to analyse additional samples and apply rigorous new sample preparation techniques. These techniques, developed by team member Dr Matt Kilburn from the University of Western Australia, will be used to identify authentic biomarkers and improve our understanding of the nature and diversity of ancient life.
Editor's Note: Original news release can be found here.
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