Paleontologists assume that microbial life forms already existed around 3.5 billion years ago. However, insights into the diversity of the ecosystems of the time have so far been limited. A research team led by Manuel Reinhardt from the University of Göttingen has now discovered new pieces of the puzzle for reconstructing complex microbial communities from this time. The missing element was provided by a rock sample from the Barberton greenstone belt in South Africa, whose rocks are among the oldest on the earth’s surface.
In the cylindrical drill sample, the researchers found evidence of an unprecedentedly diverse carbon cycle that was around 3.42 billion years old and involved various microorganisms. They proved this when they examined the rock samples and the particles of organic material they contained – the remains of former living beings – using various analytical methods, such as microscopy and spectroscopic methods. This enabled them to identify biological traces in the rock and distinguish them from subsequent contamination.
Reinhardt and his colleagues discovered the geochemical “fingerprints” of different microbes, including phototrophs, sulfate-reducing and probably methane-producing organisms. “By discovering organic matter in primary pyrite crystals and analyzing carbon and sulfur isotopes on the materials, we were able to distinguish individual microbial metabolic processes,” says senior author Henrik Drake from Linnänus University in Sweden.
The findings indicate that our planet’s microbial life diversified much earlier than previously thought. “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,” says Reinhardt. The study opens a rare window into Earth’s early ecosystems: “Our findings significantly advance the understanding of ancient microbial ecosystems and pave new paths for research in the field of paleobiology.”