Researcher: With cell densities of over 1,000 per square millimeter and a diversity of producers and consumers, these microfossils represent a functioning terrestrial ecosystem, not just a few stray cells.
“Life was not only present but thriving in soils of the early Earth about two thirds of the way back to its formation from the solar nebula,” Retallack said. The origin of the solar system — and Earth — occurred some 4.6 billion years ago.
The study outlines a microbiome of at least five different kinds of microfossils recognized from their size, shape and isotopic compositions. The largest and most distinctive microfossils are spindle-shaped hollow structures of mold-like actinobacteria, still a mainly terrestrial group of decomposers that are responsible for the characteristic earthy smell of garden soil.
Other sphere-shaped fossils are similar to purple sulfur bacteria, which photosynthesize organic compounds in the absence of oxygen while leaving abundant sulfate minerals in the soil.
“With cell densities of over 1,000 per square millimeter and a diversity of producers and consumers, these microfossils represent a functioning terrestrial ecosystem, not just a few stray cells,” said Retallack, a professor in the Department of Earth Sciences and director of paleontology collections at the Museum of Natural and Cultural History. “They are evidence that life in soils was critical to the cycles of carbon, phosphorus, sulfur and nitrogen very early in the history of the planet.” Paper. (paywall) – Gregory J. Retallack, David H. Krinsley, Robert Fischer, Joshua J. Razink, Kurt A. Langworthy. Archean coastal-plain paleosols and life on land. Gondwana Research, 2016; 40: 1 DOI: 10.1016/j.gr.2016.08.003More.
File under: Older than thought. Less time for Darwinian evolution to work.
See also: Australian vegetation 40 to 50 million years older than thought?
Early bird five million years older than thought
Bat family 36 million years older than thought
What we know and don’t know about the origin of life
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