Our planet’s first breath

Oxidized iron can be seen in these 2.1 billion ancient rocks, indicating the presence of oxygen in the atmosphere.

Cyanobacteria (a blue-green algae) must have arisen as early as 3.5 billion years ago and at least 2.9 billion years ago, according to US researchers at the Massachusetts Institute of Technology. These bacteria were the first to be able to photosynthesise. They extracted energy from sunlight and water, and in the process produced oxygen.

The formation and enrichment of oxygen in the atmosphere was necessary to raise life on our planet above the level of single cells and to create very diverse animals and plants. The process was so important that biologists call it capitals: they speak of great oxidation.

The timing of the “oxygen revolution” was already known: about 2.4 billion years ago, the concentration of oxygen in the atmosphere suddenly rose sharply. And now, with the development of the first cyanobacteria, American researchers have also been able to determine the origin of the source of oxygen. They did this by researching what is called horizontal gene transfer. Organisms transmit mutations to each other without being directly related to each other.

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This allowed the researchers to identify a common ancestor of all current cyanobacteria that must have lived about 2.9 billion years ago. At the same time, they found that the first blue-green algae may have separated from other primitive bacteria about 3.4 billion years ago.

This timing means that there are at least 500 million years between the emergence of cyanobacteria and the oxygen revolution. So it’s possible that the first blue-green algae had not yet fully mastered oxygen production, so it took ‘some time’ before they were really exposed to the vapor.

Or does the variable length of the solar day have something to do with it? Our planet is known to have rotated at a faster speed during its early childhood, up to four times faster than it does today. As a result, the day could have lasted only six hours. According to German biologists, the lengthening of days allowed cyanobacteria to gain the upper hand over other bacteria that did not photosynthesize. It is said that the slowing down of the Earth’s rotation was due to the Moon and its gravity. The length of the current day was completed more than two billion years ago, which is close to the timing of the oxygen revolution.

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