Life on land is older than expected

Microorganisms colonized the mainland 300 million years earlier than previously known

The Barberton Greenstone Belt in South Africa: Where rocky grasslands are today, a river flowed 3.2 billion years ago, at the level of which soil organisms lived. © Sami Nabhan / FSU Jena
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From water to land: The first living creatures have already made this leap at least 3.2 billion years ago - 300 million years earlier than previously thought. At least that suggests telltale crystal structures in rock formations in South Africa. These indicate the presence of microorganisms that even then lived outside the oceans.

For a long time, life on earth took place exclusively in the water. But at some point, the first creatures began to conquer the mainland - but only gradually and step by step. Because the jump out of the oceans was a difficult challenge for many animals and plants.

But when did the first organisms manage to colonize the land masses of our planet? Apparently earlier than thought, scientists now say Sami Nabhan of the Free University of Berlin. You have discovered amazing ancient traces of life in primeval rock formations in South Africa.

Microorganisms converted sulfur

In a 3.22-billion-year-old layer of the Barberton Greenstone Belt, one of the world's oldest known rocks, the researchers had discovered telltale crystal structures: tiny grains of the mineral pyrite, which showed clear signs of microbial influence.

In particular, the distribution of trace elements and the ratio of sulfur isotopes 34-S and 32-S in the iron sulfide were striking. Using mass spectrometry, Nabhan and his colleagues were able to show that the 34S fraction in the core of the crystals differs characteristically from the 34S fraction in their margins - an indication that microorganisms have converted the sulfur at the edge of the crystals, Experts call this process biogenic fractionation. display

Proof of soil organisms beyond the oceans

Due to the composition of the rock, the stratification and the shape of the crystals, the scientists assume that the rocks had their origin in an old soil profile. This "Pal oboden" was created more than three billion years ago in a river plain of a so-called Zopfstroms. The river transported sediments containing iron sulphides and deposited them in the plain.

At this level, microorganisms must have lived in a soil zone that was alternately moist and dry, causing the typical margins of the pyrite crystals. According to the researchers, soil organisms have been detected that lived outside the oceans at least 3.2 billion years ago. A novelty: The jump of the first living beings ashore is therefore about 300 million years further back than previously known. (Geology, 2016; doi: 10.1130 / G38090.1)

(Helmholtz Center Potsdam - German Research Center for Geosciences GFZ, 08.11.2016 - DAL)