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Root NationNewsComplex life on Earth may be much older than we thought

Complex life on Earth may be much older than we thought

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All life on Earth probably arose from a single spark in the early history of the Earth. After some time, it diversified, branching out into species that helped it survive. The exact timing of these moments has been the subject of controversy in the scientific community, but a new study suggests that both steps may have taken place earlier than previously thought. The study, conducted by researchers at University College London, is based on evidence of diverse microbial life inside a fist-sized piece of rock from Quebec, Canada, ranging in age from 3.75 to 4.28 billion years.

In 2017, researchers who discovered it suggested that the structures in the rock – tiny threads, protrusions and tubes – were left by ancient bacteria. But not everyone was convinced that these structures, which would push the date of the first signs of life on Earth, by at least 300 million years, are of biological origin.

Складне життя могло зародитися на Землі набагато раніше, ніж ми думали
Pink stone with dark black stripes and white threads. The threads visible here are stem-like structures that indicate the oldest known fossils.

However, after further extensive analysis of the rock, the team found an even larger and more complex structure than those previously identified. Inside the rock was a stem-shaped structure with parallel branches on one side nearly a centimeter long, as well as hundreds of distorted spheres or ellipsoids next to tubes and threads. “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,” says lead author of the study, geochemist Dominic Papineau from UCL.

A key question for Papineau and his colleagues was whether these structures could have formed as a result of non-living chemical reactions. According to the article, some of the smaller structures may have been the product of abiotic reactions, but the recently identified “tree-like” trunk is likely to be of biological origin, as no structure like this has been created by chemical reactions alone before. In addition to structures, researchers have found mineralized chemicals in the rock that could be by-products of various types of metabolic processes. Chemicals are consistent with the processes of energy recovery by bacteria, which would include iron and sulfur. Depending on the interpretation of the chemical characteristics, there may even be hints on a version of photosynthesis.

This discovery points to the possibility that the early Earth – 300 million years after its formation – was inhabited by many microbes. The rock was analyzed using a combination of optical observations using Raman microscopes (which use light scattering to determine chemical structure) and digitally reproducing areas of the rock using a supercomputer that processed thousands of images using two high-resolution imaging techniques.

The rock fragment in question was collected by Papineau in 2008 from the Nuvvuagittuq Supracrustal Belt in Quebec (NSB), which was once part of the seabed. NSB contains some of the oldest sedimentary rocks known on Earth. Fossil rocks were also analyzed at the rare earth elements level, and researchers found that it indeed contained same levels as other ancient rock specimens, confirming that it was as old as the surrounding volcanic rocks.

Складне життя могло зародитися на Землі набагато раніше, ніж ми думали
Bright red iron and a silica-rich rock that contains tubular and filamentous microfossils.

Prior to this discovery, the earliest fossil evidence of life dated back to 3.46 billion years was found in Western Australia. However, there is controversy as to whether these fossils were of biological origin.

Perhaps the most fascinating consequence of this discovery is what it means for the potential distribution of life in the universe. If life could evolve in the harsh conditions of a very early Earth, it may be more common in space than we think.

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