Fossils of bacteria 2.5 billion years old have been found

A team of geologists announces the discovery of fossilized bacteria in South Africa. 2.52 billion years old, they would have appeared well before the advent of oxygen in the atmosphere.

Beneath a layer of hard, silica-rich rock in the Kaapvaa craton centered in South Africa’s Limpopo province, geologists have found microstructures believed to be ancient fossilized bacteria 2.52 billion years old. of years. An important discovery that lifts the veil on the diversity of life and ecosystems that remained before the Great Oxidation, an ecological crisis that occurred 2.4 billion years ago in the oceans and the Earth’s atmosphere.

Evidence of these life forms is scarce and therefore exceptional. Presented in the journal Geology of the Geological Society of America, the study led by geologist Andrew Czaja of the University of Cincinnati suggests that these microfossils are most likely those of microbes that feed on sulfur, oxygen not yet being present at the time for lack of algae to synthesize it. At the time, oxygen levels in the atmosphere were less than a thousandth of 1% of what they are today). They are real vestiges of ancient times which are described by the researcher as  » unusually large, spherical in shape, smooth-walled and much larger than most modern bacteria « .

 » These fossils represent the oldest known living organisms in very dark deep water.”, explains Andrew Czaja.  » These bacteria existed two billion years before plants and trees evolved around 450 million years ago « .

For those who missed this chapter in history, the Great Oxidation, which occurred 2.4 billion years ago, describes a critical period in Earth’s early history when the global population of cyanobacteria, photosynthetic organisms like those at the origin of stromatolites, would have become numerous enough to release large quantities of oxygen into the oceans. The latter then contained a lot of iron in solution and this naturally reacted with the oxygen which then accumulated in the atmosphere for the first time.

This period is also credited with incubating Earth’s first mass extinction. The oceans were indeed full of these bacteria that metabolized their food without the need for oxygen or sunlight. The Great Oxidation in progress, these bacteria then began to « breathe » poison before dropping like flies.

Due to the lack of direct evidence from that time, it is still unclear how or when exactly these bacteria appeared, but these microfossils give a nice glimpse of what these primitive life forms looked like ages ago. least 2.52 billion years old. A discovery that also gives hope of one day finding simple forms of life on planets where oxygen is scarce.


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