Remnants of 3.5 Billion-Year-Old Bacteria May Be the Oldest Evidence of Life on Earth

Researchers working in the remote Pilbara region in Western Australia say they have found evidence what is likely the earliest example of life on earth. Sediments they unearthed in a rock body called the Dresser formation show waves of sediment indicative of complex microbial life, the Guardian reports. The 3.5 billion-year-old sediments outdate previous evidence of life around 300 million years, the researchers say.

Ripples mark the spot: Ancient sediment from the Dresser formation (a) and ripples evidencing microbial life (b). Photo: Nofke et al., Astrobiology

The team based their conclusions on evidence of “microbially induced sedimentary structures,” or MISS, i09 reports.

These structures were created by “microbial mats” — highly diverse microscopic communities of bacteria that responded to changes in physical sediment dynamics. These layers are frequently found in a wide variety of environments, including tidal flats, lagoons, riverine shores, and lakes. MISS become the final resting place for these microbial mats, which then become a fixture of the geological record.

When the microbes first formed those sediment layers, they were the dominant and most advanced life forms on the planet. Back then, the air was full of noxious sulphur and most of the planet was covered in water. It would take another billion years or so before life took the next leap in the complexity ladder, with the formation of cell nucleoli, the Guardian writes.

More from Smithsonian.com:

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The Origins of Life

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Rachel Nuwer is a freelance science writer based in Brooklyn.