Australian Fossils From 3.4 Billion Years Ago Are Similar To Modern Bacteria

Back in 2013, scientists discovered fossils from 3.4 billion years ago at a formation called Strelley Pool in Western Australia. It looked like the remains of an ancient bacteria back in the day and a thorough analysis of its chemical composition revealed that it is very similar to modern-day bacteria.

Earth is believed to be nearly 4.5 billion-years-old, which means the rare microfossil was deposited not long after the birth of our planet. This drew immediate attention from archaeologists around the globe. However, it wasn’t immediately clear if the fossils were from an early form of life.

Billions of years is a very long time and over this period, any fossil, be it a bone or a microscopic organism, can degrade easily. This marked a debate over the status of the super-old microfossil discovered in Australia.

However, an international team of researchers are finally giving us more insight into the history of these fossils and putting them among the top candidates for the oldest ever evidence of life found on Earth.

All of this was made possible with sophisticated chemical analysis. The team employed synchrotron-based X-ray absorption spectroscopy and a range of techniques to analyze the chemical remains of the tiny fossils like never before.

The results of the work were then compared with the chemical make-up of another set of microfossils, one that got buried at Canada’s Gunflint Formation some 1.9 billion years-ago — much later in Earth’s history. The team also took modern-day bacteria into the study to note the differences.

Surprisingly, the observation of the research revealed that the chemical remains of the ancient microfossil are pretty similar to that of both subjects included in the study. Essentially, they all had the same absorption features, which suggest origin from the same kind of building blocks for all three cases.

This indicated that the 3.4 billion-year-old microfossil likely originated from an early form of life, just like the other two subjects.

“We demonstrate that the elemental and molecular characteristics of these 3.4 Ga microfossils are consistent with biological remains, slightly degraded by fossilization processes,” Jullien Alleon from MIT, the lead author of the study, said in a statement. “This effectively supports the biological origin of the Strelley Pool microfossils.”

As per the researchers, the Australian microfossils were much more well preserved than the more recent Canadian fossils, possibly due to the nature of rocks in which they were buried. In fact, the analysis has shown they have been subjected to temperatures as high as 300 degrees Celsius (572 degrees Fahrenheit) over the last 3.4 billion years.

"Yet we are still able to see signs of their original chemistry,” Alleon concluded. “This is a step forward to confirming that these are indeed the oldest fossils yet discovered.”

The study titled “Microfossil assemblage from the 3400 Ma Strelley Pool Formation in the Pilbara Craton, Western Australia: Results from a new locality,” was published in the journal Geochemical Perspectives Letters.