The Proterozoic era, which lasted about two billion years, played an important role in shaping the world as we now know it. This longest geological period, which occupied almost half of the general history of the planet, was marked by a series of epoch-making events that reversed the Earth's evolution.
It was the Proterozoic era that "marked" the increase in water masses in the hydrosphere so that the first seas began to merge into a single ocean of planetary scale, the level of which eventually reached the tops of the ocean ridges. This first tectonic-geochemical boundary was marked by a sharp increase in the degree of hydration of the oceanic lithospheric crust (due to the excessive saturation of rift zones with large masses of salty ocean water). This process lasted approximately six hundred million years. And this played a crucial role in the subsequent formation of the ocean floor topography.
The most ancient historical stage, the Archean, was replaced by the Proterozoic era. The climate began to change significantly with the beginning of a new era. The surface of the planet, which during the Archean period was an almost bare cold and lifeless desert with frequent glaciations, underwent significant changes closer to the middle of the Proterozoic (towards warming).
At that time, there was a significant saturation of the atmosphere with oxygen, which radically changed the direction of the evolutionary development of biological organisms. Scientists have called this fateful event, which occurred approximately two billion years ago, the “oxygen catastrophe”. This period is characterized by the nucleation of the first unicellular aerobic organisms (since the oxygen concentration in the air mixture was sufficient to ensure their vital functions). It was then that most species of anaerobic organisms became extinct, for which molecular oxygen was fatal. Which, to a large extent, predetermined the further vector of evolutionary development.
During this gigantic time interval, microorganisms and algae reached their peak. Rather intensive processes of formation of almost all sedimentary rocks, which marked the Proterozoic era, proceeded with the direct (and very active) participation of these life forms.
Eukaryotes, ousting "backward" prokaryotes from the evolutionary scene, also formed when the Proterozoic era arrived. Animals breathing air, by the way, appeared on the planet in the same historical period. Most species of fauna of the Late Proterozoic era have already been represented by multicellular eukaryotic forms. The end of this era may well be called the "century of jellyfish", which then prevailed on the planet. At the same time, annelid worms (progenitors of mollusks and arthropods) arose.
The Proterozoic era was a grandiose historical period, during which the undivided rule of the eukaryotic cell began. Primitive unicellular and colonial life forms began to be replaced by multicellular highly organized beings. Life itself has become an important factor in geological evolution. Living organisms began to take an active part in changing the composition and shape of the earth's crust, they became the basis of its upper layer - the biosphere. Photosynthesis came to Earth , the importance of which cannot be overestimated. It was he who changed the composition of the atmosphere so much , having saturated it with a huge amount of oxygen, that it became possible to develop higher heterotrophic organisms - highly organized animals.
Thus, optimal conditions were created for the arrival of a higher life form in this world - a person who was destined to change the face of the planet in a brief moment of its existence (only 500 thousand years - one instant by the standards of geology!) Beyond recognition. And at the same time, to give the concepts of "life" and "evolution" a completely new meaning ...