Evolution: first life fossils on Earth (Introduction)

by David Turell , Friday, November 11, 2022, 00:06 (534 days ago) @ David Turell

Stromatolites in Australia:

https://www.livescience.com/oldest-stromatolites-australia?utm_campaign=368B3745-DDE0-4...

"Layered rocks in Western Australia are some of Earth's earliest known life, according to a new study.

"The fossils in question are stromatolites, layered rocks that are formed by the excretions of photosynthetic microbes. The oldest stromatolites that scientists agree were made by living organisms date back 3.43 billion years, but there are older specimens, too. In the Dresser Formation of Western Australia, stromatolites dating back 3.48 billion years have been found.

"However, billions of years have wiped away traces of organic matter in these older stromatolites, raising questions about whether they were really formed by microbes or whether they might have been made by other geological processes.

"'We were able to find certain specific microstructures within particular layers of these rocks that are strongly indicative of biological processes," said Keyron Hickman-Lewis(opens in new tab), a paleontologist at the Natural History Museum in London, who led the research.

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"Hickman-Lewis and his team examined Western Australian stromatolites first discovered in 2000 by study co-author Frances Westall(opens in new tab) at the National Center for Scientific Research (CNRS) in France. They used a variety of high-resolution 2D and 3D imaging techniques in order to peer into the layers of the stromatolite at a fine scale.

:What they saw hinted at biological growth in all its messy glory. The researchers observed uneven layers, including little dome shapes that are indicative of photosynthesis, since microbes with the most access to the sun will grow more vigorously than those not as high in the structure. They also saw columnar structures that are typical in modern stromatolites, which are still found in a few locations around the globe.

"Microbial mats give you layers that are uneven in their thickness and tend to be wrinkly or crinkly or go up and down on very small spatial scales," said Linda Kah(opens in new tab), a sedimentologist and geochemist at the University of Tennessee who was not involved in the new study. Putting all the structural clues together, she told Live Science, "you end up with what looks like the characteristics of a microbial mat."

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"The evidence that the Dresser Formation stromatolites are signs of ancient life doesn't make them the oldest life on the planet. That (possible) honor may go to stromatolites found in 3.7 billion-year-old rock in Greenland, or possibly to microfossils from Canada that might be as old as 4.29 billion years. It's very difficult to distinguish biological life from non-organic processes in these very old rocks, however, so these finds and others from a similar timeframe are controversial.

"Based on the minerals in the stromatolites, the Western Australia microbial mats probably formed in a shallow lagoon fed by hydrothermal vents that was also connected to the ocean, the researchers reported Nov. 4 .

Comment: We've been here before. If any of these fossil spots are real life, it makes the point that life did not take long to appear after the Earth formed and was going through constant bombardment in what is called Earth's 'Hadean period'. It looks as if life was pre-ordained to appear. Not by chance.