The research team has made a fascinating discovery: they've found complex microbial communities in ecosystems that date back over 3 billion years.
Microorganisms are thought to be the earliest life forms on Earth, with evidence found in rocks that are a staggering 3.5 billion years old. These rocks contain telltale signs, like specific chemical compounds and structures, left behind by these ancient organisms.
Despite this evidence, the exact origins of life on Earth and the development of diverse species within these early microbial communities remain unclear, with evidence often scarce and subject to debate.
But now, researchers led by the University of Göttingen and Linnӕus University in Sweden have shed new light on these early life forms. In rock samples from South Africa, they've uncovered evidence dating back to around 3.42 billion years ago, revealing a remarkably diverse carbon cycle involving various microorganisms. Their findings, published in the journal Precambrian Research, show that complex microbial communities were already thriving during the Palaeoarchaean period.
To uncover these ancient secrets, the researchers analyzed well-preserved particles of carbonaceous matter – the altered remains of living organisms – and the corresponding rock layers from samples of the Barberton greenstone belt in South Africa. These rocks are among the oldest on Earth's surface. By combining macro and micro analyses, the scientists were able to clearly identify original biological traces and distinguish them from later contamination. They identified geochemical "fingerprints" of various microorganisms, including those that likely used sunlight for energy, metabolized sulfate, and possibly produced methane. By combining geochemical data with findings on the texture of the rocks obtained from thin-section analysis with a microscope, the researchers determined the respective role of these microorganisms in the carbon cycle of the ecosystem at the time.
Dr. Henrik Drake from Linnӕus University, the senior author of the study, explains, "By discovering carbonaceous matter in primary pyrite crystals and analyzing carbon and sulfur isotopes in these materials, we were able to distinguish individual microbial metabolic processes."
Dr. Manuel Reinhardt, the first author of the study from Göttingen University's Geosciences Centre, adds, "We didn’t 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 early ecosystems and significantly advances our understanding of ancient microbial ecosystems, opening up new avenues for research in the field of palaeobiology.
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