Science

Researchers unearth 3.5 billion year old ‘Oldest Known’ fossil

Study of controversial fossils proposes that life may have started on Earth 4 billion years ago

Researchers have confirmed that tiny fossils found in a nearly 3.5 billion-year-old piece of rock in Western Australia are the prehistoric fossils ever found and certainly the earliest direct proof of life on Earth. Researchers discovered proof of what was then probably the earliest life on Earth: 3.5-billion-year-old tiny squiggles encased in Australian rocks. Since then, however, investigators have questioned whether these marks genuinely represent ancient microorganisms, and even if they do, they’re that old. Now, a comprehensive review of these microfossils recommends that these formations do indeed depict ancient microbes, ones potentially so difficult that life on our planet must have started some 500 million years earlier.

The new work indicates these new microorganisms were surprisingly mature, able of photosynthesis and of handling other chemical methods to get energy, says Birger Rasmussen, a geobiologist at Curtin University in Perth, Australia. The study “will apparently touch off a flurry of a new investigation into these rocks as other researchers study for data that either support or disprove this new statement,” Alison Olcott Marshall, a geobiologist said.

In the late research, William Schopf, a paleobiologist at the University of California, Los Angeles and the discoverer of the Australian microfossils teamed up with John Valley, a geoscientist at the University of Wisconsin in Madison. Valley is an expert in an analytical technique called secondary ion mass spectrometry, which can define the ratio of different forms of carbon in a sample key to calculating whether it’s organic. Based on this data, the researchers were also able to assign identities and likely physiological behaviours to the remains locked inside the rock, Valley states. The results show that “these are primaeval, but diverse group of organisms,” states Schopf.

The team classified a sophisticated group of microbes: phototrophic bacteria that would have relied on the Sun to generate energy, Archaea that generated methane, and gammaproteobacteria that absorbed methane, a gas considered to be an essential component of Earth’s early climate before oxygen was present.

It took Valley’s team nearly ten years to develop the processes to sift through the microfossils, fossils this old and unique have never been subjected to SIMS investigation before. The research builds on earlier accomplishments at WiscSIMS to transform the SIMS instrument, to develop rules for sample preparation and analysis, and to calibrate assured standards to match as nearly as possible the hydrocarbon content to the specimens of interest.

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Saloni Sharma

Saloni Sharma is an environmental activist with broad, deep experience in print and online writing, publication and site management, news coverage, and editorial team management.

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