Can microfossils solve the ‘early life’ mystery

Anew study could help settle arguments over which microfossils are signs of early life and which are not. The study was published in the journal 'Geology'. The new experiments by geobiologists Julie Cosmidis, Christine Nims, and their colleagues have shown that fossilized spheres and filaments – two common bacterial shapes – made of organic carbon (typically associated with life) can form abiotically (in the absence of living organisms) and might even be easier to preserve than bacteria.

“One big problem is that the fossils are a very simple morphology, and there are lots of non-biological processes that can reproduce them,” Cosmidis said. “If you find a full skeleton of a dinosaur, it is a very complex structure that is impossible process to added.

It’s much harder to have that certainty with fossilized microbes. Their work was spurred by an accidental discovery a few years back, with which both Cosmidis and Nims were involved while working in Alexis Templeton’s lab.

While mixing organic carbon and sulfide, they nofor a chemical reproduce,” he ticed that spheres and filaments were forming and assumed they were the result of bacterial activity. But on closer inspection, Cosmidis quickly realised they have formed abiotically.

The researchers noted that very early they “noticed that these things looked a lot like bacteria, both chemically and morphologically.” “They start just looking like a residue at the bottom of the experimental vessel,” researcher Christine Nims said.

Nims set about running the new experiments, testing to see if these abiotic structures, which they called biomorphs, could be fossilized like a bacterium would be. By adding biomorphs to a silica solution, they aimed to recreate the formation of chert, a silica-rich rock that commonly preserves early microfossils.

For weeks, she would carefully track the smallscale ‘fossilization’ progress under a microscope. They found not only that they could be fossilized, but also that these abiotic shapes were much easier to preserve than bacterial remains. The abiotic 'fossils,' structures composed of organic carbon and sulfur, were more resilient and less likely to flatten out than their fragile biological counterparts.