We've learned a lot about life that came before us by studying fossils. The ancestry and evolution of ancient microbial life, however, has been more challenging to decipher because microbes don't leave fossils like those left by animals. But in recent years, researchers have been discovering fossils that they hypothesize are the remnants of ancient microbes. Some of the oldest of these fossils, which have been found in several places including Canada and Western Australia, have been estimated to be from 3.4 to 3.7 billion years old, if you agree that the specimens represent once-living creatures.
These fossils are filaments and tubes made of hematite, a form of rust or iron oxide. Researchers have suggested that these samples could have only arisen through biological processes, and are made of materials that would be expected from the decomposition of an organism.
In a new study reported in Science Advances, researchers outlined the discovery of more of these filamentous fossils, which they estimate to range in age from 3.75 to 4.28 billion years old.
In 2008, samples were taken from Quebec’s Nuvvuagittuq Supracrustal Belt (NSB), an area that was once a seafloor, and is thought to house some of the oldest sedimentary rocks on Earth. In this study, a detailed assessment of these samples was performed with a variety of tools including microtomography and focused ion beam microscopy.
The researchers made very thin slices of those rock samples, to create 3D representations of everything, inside and out; it revealed branching structures and twisting filaments through the rock. There are some marine microbes living now near hydrothermal vents that bear a resemblance to these structures, noted the researchers. The team concluded that these shapes could not have been made from geological forces in the rock.
The analysis indicated that the rock surrounding the fossils was full of the byproducts of microbial metabolism. These ancient microbes may have consumed iron, sulphur, and potentially, carbon dioxide or light in a process that may resemble photosynthesis. The age of the specimens was verified as well.
If there were living organisms on Earth this long ago, “This means life could have begun as little as 300 million years after Earth formed. In geological terms, this is quick – about one spin of the Sun around the galaxy,” noted lead study author Dr. Dominic Papineau of the University College of London.
This study also suggested that if life can arise this quickly, then it seems to increase the likelihood that there are life forms on other planets, added Papineau.