a way of life that is 2 billion years old

Last July, we discovered that a rock at the bottom of the sea had “corrected” the origins of complex life 1.5 billion years earlier. They discovered environmental conditions for animal life in the Franceville Basin (Gabon), sediments that were deposited about 2.1 billion years ago. Now science has just discovered the oldest form of life ever discovered in these conditions.

Studying. A team from the University of Tokyo’s Department of Earth and Planetary Sciences found that a sealed crack in rock nearly 15 meters underground had harbored microbes for the past 2 billion years, according to a study published in the journal Microbial Ecology.

A nearly 30cm-long specimen excavated beneath the Bushveld volcanic complex in South Africa is reported to surpass previous microbial record holders by 1.9 billion years. An amazing discovery that could help researchers better understand the early stages of evolutionary life not only on Earth, but also beyond.

Rewriting “antiquity”. As Yohei Suzuki of the University of Tokyo and lead author of the study explains, until now it was not known whether the 2-billion-year-old rocks were habitable; “the oldest geological layer in which living microorganisms were found was a 100-million-year-old deposit. years under the ocean floor, so this is a very exciting discovery.”

As the researcher reminds, such discoveries are key because by studying the DNA and genomes of such microbes, we can understand the evolution of very early life on Earth.

“House” of microbes. The microbes were found inside a sealed crack in ancient rock, an “intrusion” of rock formed when magma slowly cooled beneath the Earth’s surface. The space where the whole process took place – the Bushveld Igneous Complex – is not just any place. The complex occupies a gigantic area and contains some of the richest ore deposits on Earth, including about 70% of the world’s platinum.

The fact that the enclave has remained relatively unchanged since its formation is precisely what provided the ideal conditions in which ancient microbial life was able to survive.

Life of a microbe. In the question of how the Earth can survive for billions of years, the key lies in the slowness of all processes. These organisms, living far below the Earth’s surface, evolve incredibly slowly and have very slow metabolic rates, meaning they can persist in igneous rocks over geological time scales of at least 2 billion years, recent research has shown.

Meeting. To get to the sample, the researchers drilled 15 meters underground until they found and recovered a 30-centimetre-long piece of rock core. Further analysis revealed densely packed living microbial cells in the cracks of the rock, isolated from the outside environment by clay-filled voids.

Then it remained to make sure that the organisms were indeed “native” to the breed. To do this, they stained the microbes’ DNA and used infrared spectroscopy to observe the proteins they contained, as well as those in the surrounding clay. During the work, it was established that the organisms were alive and not infected. They have been there for at least 2 billion years.

From Earth to Mars. As they state at the end of their published work, once these are confirmed to be the oldest living microbes ever found in rock samples, their significance will extend far beyond our planet. In fact, the research team hopes that their additional discoveries could also help in the search for evidence of life on Mars.

“NASA’s Perseverance rover on Mars plans to return rocks that are the same age as the ones we used in this study. Finding microbial life in samples from Earth from 2 billion years ago and being able to accurately authenticate them makes me excited about what we can now find in samples from Mars,” says Suzuki.

Image | Y. Suzuki, S.J. Webb, M. Koduka et al. 2024/ Microbial ecology

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