State-of-the-art technology at The University of Western Australia has helped to rewrite the history of major groups of life on the planet.
A team of Australian researchers, including UWA's Dr Matt Kilburn, have revised estimates of the earliest oxygen-producing bacteria on earth by 500 million years.
The findings, published in the latest edition of the journal Nature, challenge previous research that claimed the earliest existence of the microbes that produce oxygen by photosynthesis - cyanobacteria - was 2.7 billion years ago.
Using UWA's state-of-the-art NanoSIMS ion microprobe, they found that biomarkers on 2.7 billion year old rocks were probably contaminated and not evidence of the earliest cyanobacteria.
In the absence of the biomarker evidence, the oldest unambiguous fossil evidence for cyanobacteria is about 2.2 billion years old (although they must have been present during the "Great Oxidation Event" between 2.45 and 2.32 billion years ago).
The implications for the evolution of more complex cells (known as eukaryotes), which are the basis of higher organisms such as fungi, plants and animals, are also profound. The revised time line places the first appearance of eukaryotes at about 1.7 billion years ago, well after the rise in atmospheric oxygen.
The accumulation of oxygen irreversibly transformed the Earth's surface, leading to the oxygenation of the atmosphere and oceans and, according to some, triggering severe global glaciations ("snowball Earth"). It profoundly changed biogeochemical cycles and ultimately paved the way for the appearance of large aerobic organisms, including animals.
The Australian scientists - Prof Birger Rasmussen and Dr Ian Fletcher at the Curtin University of Technology in Perth, Western Australia, Dr Jochen Brocks from the Australian National University and Dr Matt Kilburn from The University of Western Australia, re-examined the biomarker evidence from the 2.7 billion year old rocks.
Organic compounds (biomarkers) taken from the rocks, and previously thought to be as old as the rocks, were compared to droplets of solidified oil (less than a hundredth of a millimetre in diameter) from the rock itself using the NanoSIMS ion microprobe.
The researchers found that the composition of the solidified oil was distinctly different to the composition of the biomarkers and probably represent contaminants, possibly introduced from younger sedimentary rocks or during drilling or sample handling.