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Microorganisms were the first forms of life on our planet. The clues are written in 3.5 billion-year-old rocks through geochemical and morphological traces, such as chemical compounds or structures that these organisms left behind. However, it is still unclear when and where life originated on Earth and when a diversity of species developed in these early microbial communities. The evidence is scarce and often controversial. Now, researchers led by the University of Göttingen and Linnäus University in Sweden have uncovered key findings about early life forms. In rock samples from South Africa they found evidence dating back to about 3.42 billion years ago of an unprecedented carbon cycle in which various microorganisms participated. This research shows that complex microbial communities already existed in ecosystems during the Paleoarchean period. The results were published in the journal. Precambrian research.
The researchers analyzed well-preserved particles of carbonaceous matter (the altered remains of living organisms) and corresponding rock layers from samples from the Barberton Greenstone Belt, a mountain range in South Africa whose rocks are among the oldest on the surface of the earth. The scientists combined macro and micro analyzes to clearly identify the original biological traces and distinguish them from later contamination. They identified geochemical “fingerprints” of several microorganisms, including those that must have used sunlight for energy, metabolized sulfate, and probably also produced methane. The researchers determined the respective role of microorganisms in the carbon cycle of the ecosystem at that time by combining geochemical data with findings on rock texture obtained by analyzing thin sections with a microscope. “By discovering carbonaceous matter in primary pyrite crystals and analyzing the carbon and sulfur isotopes in these materials, we were able to distinguish individual microbial metabolic processes,” explains the study’s lead author, Dr. Henrik Drake from Linnäus University.
First author Dr. Manuel Reinhardt from the Center for Geosciences at the University of Göttingen adds: “We did not expect to find traces of so many microbial metabolic processes. It was like the proverbial search for a needle in a haystack.” The study provides a rare glimpse into Earth’s first ecosystems. “Our findings significantly advance the understanding of ancient microbial ecosystems and open new avenues for research in the field of paleobiology.”