New pieces in the puzzle of first life on Earth

The researchers analysed 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. They identified geochemical “fingerprints” of various microorganisms, including those that must have used sunlight for energy, metabolised sulphate 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 analysing carbon and sulphur 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.”