Scientists have analyzed rocks from Western Australia and discovered traces of bacteria that might have existed 3.49 billion years ago—a mere billion years after our planet formed.
If the find upholds the scrutiny that usually faces claims of fossils this old, it could move scientists one step closer to understanding the first chapters of life on Earth. The discovery could also aid in the search for life on other planets.
According to Nora Noffke, a biogeochemist at Old Dominion University in Norfolk, Virginia, these traces of bacteria “are the oldest fossils ever described. Those are our oldest ancestors,” Noffke, was part of the group that made the find and presented it last month at a meeting of the Geological Society of America.
Unlike dinosaur bones, the newly identified fossils are not petrified body parts. They’re textures on the surfaces of sandstone thought to be sculpted by once-living organisms. Today, similar patterns decorate parts of Tunisia’s coast, created by thick mats of bacteria that trap and glue together sand particles. Sand that is stuck to the land beneath the mats and thus protected from erosion can over time turn into rock that can long outlast the living organisms above it.
Finding the earliest remnants of this process required a long, hard look at some of the planet’s oldest rocks, located in Western Australia’s Pilbara region. This ancient landscape was once shoreline. Rocks made from sediment piled up billions of years ago are now exposed and available for examination. Relatively pristine in condition, such outcrops, along with others in South Africa, have long been a popular place to look for traces of life from the Archean eon, which ended 2.5 billion years ago.”
Although there are older rocks on Earth, those most likely to preserve the tiny structures and chemicals that give evidence of life are those found in Western Australia. Maud Walsh, a biogeologist at Louisiana State University said, “These are the best-preserved sedimentary rocks we know of, the ones most likely to preserve the really tiny structures and chemicals that provide evidence for life.” Another team of researchers last year published the discovery of microscopic fossils in Pilbara’s Strelley Pool Formation, about 3.4 billion years old.
It’s a lot more than the interest of the find, it’s showing that life has some organization to it. The ridges that crisscross the rocks like the strands in a spider’s web hint that bacteria linked up in sprawling networks.
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