Biologists know when oxygen appeared on Earth

Previously, scientists believed that global changes in the atmosphere associated with a sharp increase in oxygen

happened at the very beginning of the Proterozoic, about 2.45 billion years ago. Cyanobacteria, which produce oxygen, are responsible for this. 

These bacteria produced oxygen before, butit was completely spent on the oxidation of rocks, compounds dissolved in sea water and atmospheric gases. But at one point its number unexpectedly increased. 

In evolution, everything always starts small.While there is evidence for early oxygenic photosynthesis, which is the most important and truly amazing evolutionary innovation on Earth, it took hundreds of millions of years for it to really work.

Greg Fournier, Associate Professor of Geobiology, Department of Earth, Atmospheric and Planetary Sciences

The authors of the new work wanted to find out how muchtime, cyanobacteria produced oxygen before a sharp jump in its volume occurred. Researchers created a special gene analysis technique and found that all types of cyanobacteria that exist on Earth today descended from one ancestor.

It appeared about 2.9 billion years ago. And its predecessors split off from other bacteria about 3.4 billion years ago. At this time, according to the researchers, the process of oxygenic photosynthesis arose.

The authors believe that such a serious gapbetween the two events can be explained by the fact that initially the ancestors of cyanobacteria constituted only a small proportion of the biosystem of the early Earth and produced negligible oxygen. 

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