Tracing the oldest traces of life on Earth is not easy – place a group of microbes between layers of rocks and let them mature for billions of years; What you get looks more like rocks than an ancient life form.
It takes a real eye to tell one from the other, and even then the debate rarely ends.
Take, for example, the 3.48 billion year old group of rock formations in Western Australia. These are thought to be the fossilized remains of microbial assemblages known as stromatolites, and are easier said than done to rule out the possibility that they are purely geological.
Now a new analysis by an international team of researchers provides strong evidence that these formations are of biological origin, and not the result of non-living processes.
Paleontologist Kieron Hickman Lewis of the Natural History Museum in the UK explains: “If an archaeologist discovers the foundations of a ruined city, he will know that it was built by people, because it will have all the signs of human construction – entrances, roads, bricks. Much the same a lot “This is the structural element that is the constituent of stromatolites and which allows us to determine the processes of their formation and decipher their origin. We can almost be archaeologists.”
Billions of years old stromatolites are scattered all over the world. It consists of encapsulated or micro-layered rocks, which can be formed either by microbial mineral layers or by non-living chemical reactions between the rock and its environment.
The task of a paleontologist is to try to figure out what it is—not always easy, as we saw with the 3.7 billion year old stromatolites in Greenland, which were first claimed to be the oldest fossils in the world and then just turned out to be ancient. rock fossils.
Today, 3.43 billion year old stromatolites from another Western Australian site, Strelli Pool, are the oldest traces of widely recognized life on Earth. Hickman Lewis and colleagues are subjecting 3.48 billion-year-old stromatolites from the Dresser Formation in Western Australia to a thorough new study.
They used several methods to study the 2D and 3D microstructures found in Dresser’s stromatolites, including optical microscopy and scanning electron microscopy.
None of these tests revealed microfossils or organic materials, but showed structure and properties consistent with biological origin.
The team once concluded that stromatolites were photosynthetic microbial mats living at the bottom of a shallow sea lake.
The team also observed columnar “barrier” formations consistent with rock patterns known to form through microbial growth.
These clues provide strong evidence for the biological origin of these ancient rock layers, making them the oldest evidence of life on Earth and influencing the search for life elsewhere.
The study was published in magazine geology.
Source: Science Alert.