A drill core sample from the Barberton greenstone belt used in the study. The dark layers contain particles of carbonaceous matter, the altered remains from Palaeoarchaean microorganisms. Credit: Manuel Reinhardt
The research team has discovered complex microbial communities in ecosystems dating back over 3 billion years.
Microorganisms are believed to be Earth’s earliest life forms, with evidence embedded in rocks that are 3.5 billion years old. These rocks contain geochemical and morphological markers, like specific chemical compounds and structures, that these ancient organisms left behind.
However, it is still not clear when and where life originated on Earth and when a diversity of species developed in these early microbial communities. Evidence is scarce and often disputed.
Now, researchers led by the University of Göttingen and Linnӕus University in Sweden have uncovered key findings about the earliest forms of life. In rock samples from South Africa, they found evidence dating to around 3.42 billion years ago of an unprecedentedly diverse carbon cycle involving various microorganisms. This research shows that complex microbial communities already existed in the ecosystems during the Palaeoarchaean period. The results were published in the journal Precambrian Research.
Uncovering the Past: Advanced Research Techniques
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, a mountain range in South Africa whose rocks are among the oldest on the Earth’s surface. The scientists combined macro and micro analyses to clearly identify original biological traces and distinguish them from later contamination.
The mountainous region of the Barberton greenstone belt in South Africa. Credit: Axel Hofmann
They identified geochemical “fingerprints” of various microorganisms, including those that must have used sunlight for energy, metabolized sulfate, and probably also produced methane. The researchers determined the respective role of the microorganisms in the carbon cycle of the ecosystem at the time by combining geochemical data with findings on the texture of the rocks obtained from thin-section analysis with a microscope.
“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,” explains the senior author of the study, Dr Henrik Drake from Linnӕus University.
First author Dr Manuel Reinhardt, 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 the Earth’s early ecosystems. “Our findings significantly advance the understanding of ancient microbial ecosystems and open up new avenues for research in the field of palaeobiology.”
Reference: “Aspects of the biological carbon cycle in a ca. 3.42-billion-year-old marine ecosystem” by M. Reinhardt, V. Thiel, J.-P. Duda, A. Hofmann, D. Bajnai, W. Goetz, A. Pack, J. Reitner, M. Schanofski, J. Schönig, M.J. Whitehouse and H. Drake, 12 January 2024, Precambrian Research.
DOI: 10.1016/j.precamres.2024.107289
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