Way before trees or lichens evolved, soils on Earth were alive, as revealed by a close examination of microfossils in the desert of northwestern Australia, reports a team of University of Oregon researchers.
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."
Cool thread. I often thought that the idea that all life evolved in the sea and somehow splashed up on the beach and slowly made it's way to breathing 'air' a bit of a stretch. I personally think it far more likely that life evolved everywhere, in all kinds of hostile environments. Otherwise we would not have biology living in volcanos, noxious acidic hot pools, arctic ice, and within the Earth's crust.
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