World's Oldest Fossil Found In Australia

Tiny structures found within 3.4 billion-year-old sandstones in Western Australia may represent the oldest direct evidence of life on Earth.

Scientists say their analysis of the microfossils clearly shows the organisms were processing sulphur for energy and growth - not oxygen.

The new discovery is reported in the journal Nature Geoscience.

The team says the microbe remains offer a fascinating insight into conditions on the ancient Earth.

"At last we have good solid evidence for life over 3.4 billion years ago. It confirms there were bacteria at this time, living without oxygen," said Oxford University Professor Martin Brasier, who was part of the Anglo-Australian team that made the discovery.

"Such bacteria are still common today.

"Sulphur bacteria are found in smelly ditches, soil, hot springs, hydrothermal vents - anywhere where there's little free oxygen and they can live off organic matter," he added.

The microfossils were found at a remote site in western Australia called Strelley Pool, a dry region about 60km west of Marble Bar.

The sandstones there were laid down in what would have been a shallow-water beach or estuary.

Scientists are convinced the tiny cell-like objects are biological and not mineral in origin.

The fossils are clearly preserved and show precise cell-like structures, all of a similar size.

The way they were clustered together in appropriate habitats also suggests biological behaviour.

The research may have implications for searching for signs of life on other planets.

Life on Mars or the moons of Jupiter and Saturn is likely to follow similar lines.

Any microfossils found on these worlds should pass the same evidence tests, according to the scientists.

Prof Brasier said: "Could these sorts of things exist on Mars? It's just about conceivable."