World’s oldest fossils discovered in WA

Microsfossils found in the Pilbara region of Western Australia show that more than 3.4 million years ago bacteria thrived on a warmer earth that had no oxygen. Researchers David Wacey from the University of Western Australia and Martin Brasier from Oxford University in the UK said in a report in Nature Geoscience that microbes located in sedimentary rock have been confirmed as the earliest fossils ever recorded.

The sample is from the Stanley Pool site in a remote region of Pilbara, where the microbes had been finely preserved between quartz sand grains. Pilbara has some of the planet’s oldest rocks formations, set down in the Archean Eon, when the infant earth was a primeval water world with seas that were the temperature of a hot bath. The two geologists say their chemical analyses of the minerals near the cells suggest the microorganisms depended on sulphur for fuel. The findings boost hopes life has existed on Mars.

Brasier first suspected the ancient rock formation would be a good place to look because it so closely resembled a modern beach, indicating that the sediments had not been badly heated or distorted since they were laid down. Wacey and colleagues analysed the rock formation that included this ancient shoreline to verify the beach was about 3.4 billion years old. Such a beach might have been life’s first breeding ground, Brasier says.

The work represents “some of the best evidence for the nature of Earth’s earliest life,” says Bruce Runnegar, a geologist at the University of California, Los Angeles, who was not involved in the study.