Scientists have discovered possibly the earliest signs of life on Earth—remains of bacteria that are almost 3.5 billion years old—in a remote region of north-west Australia.

Evidence of the complex microbial ecosystem was found in sedimentary rocks in the remote Pilbara region in Western Australia, an area which contains some of the world's oldest rock formations.

One of the researchers, David Wacey, from the University of Western Australia, said the newly discovered evidence of bacteria "was possibly the oldest signs of life on Earth.

"There was plenty of life from the 3.4 and 3.43 billion-year-old mark – this is pushing it further back," he told The Telegraph.

"There are slightly older claims of life in rocks in Greenland—but the rocks there have been so deformed that it is very difficult to tell if what you are seeing was actually there in the first place. With these microbial systems in the Pilbara, you can see these things in the field and under the microscope. You can see how the bacteria were interacting with the sediment they were living on."

Professor Wacey said it was no longer possible to see the actual cells, but the scientists had discovered the marks left behind by large clusters, or mats, of microbes. The traces were discovered in a body of rock called the Dresser Foundation, near the town of Port Hedland.

"We don't see the microbe themselves but we large scale structures that the microbes constructed before they died," he said.

"We see tufts and wrinkles and – when we look down the microscope – we see filaments tangled in sand grains. We are also seeing organic material which are the actual microbes but they are decomposed to the point that we cannot see an actual cell. You just see a mass of carbon-rich material." The team of scientists from Australia and the United States believes the findings may help with the search for life on other planets.

"There are applications for searching for life elsewhere and knowing what to look for," Professor Wacey said.

"These microbial mats could be seen by a Mars rover... It also helps with our understanding of when life first evolved and what sort of environment it evolved in and putting firm dates on when some pretty important things happened. Ultimately, we are looking for when that soup of chemicals became something that could be called life." The findings have been published in the journal Astrobiology.

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This article by Jonathan Pearlman was first published by The Telegraph.