The Proterozoic era: the thorny path of earthly evolution

The Proterozoic era, which lasted about two billion years, played an important role in shaping the world as we know it now. This longest geological period, which occupied almost half of the total history of the planet, was marked by a number of epoch-making events that turned the earth's evolution backwards.

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 oceanic 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 the rift zones by large masses of salty ocean water). This process lasted about six hundred million years. And this played a major role in the subsequent formation of the ocean floor relief.

The most ancient historical stage, the Archean, was replaced by the Proterozoic era. The climate with the beginning of a new era began to change significantly. The surface of the planet, which during the Archean period was practically a bare, cold and lifeless desert with frequent glaciations, has undergone significant changes towards the middle of the Proterozoic (towards warming).

At the same time, there was a significant saturation of the atmosphere with oxygen, which radically changed the direction of the evolutionary development of biological organisms. Scientists this fateful event, which occurred about two billion years ago, has already been called an "oxygen disaster". This period is characterized by the birth of the first unicellular aerobic organisms (since the concentration of oxygen in the air mixture was sufficient to ensure their vital activity). At that time, most species of anaerobic organisms died out, for which molecular oxygen was fatal. That, to a large extent, predetermined the further vector of evolutionary development.

During this giant time interval, microorganisms and algae reached their peak. Quite 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Eukaryotes that have superseded the "backward" prokaryotes from the evolutionary scene also formed when the Proterozoic era came. Animals breathing the air, by the way, appeared on the planet in the same historical period. Most fauna species of the late Proterozoic era have already been represented by multicellular eukaryotic forms. The end of this era may well be called the "jellyfish century", which then prevailed on the planet. At the same time, annelids (the progenitors of mollusks and arthropods) arose.

The Proterozoic era was a grandiose historical period, during which the undivided domination of the eukaryotic cell began. Primitive unicellular and colonial forms of life 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 the Earth , which can not be overestimated. It was he who changed the composition of the atmosphere so much , saturating it with a huge amount of oxygen, which made possible the development of higher heterotrophic organisms - highly organized animals.

Thus, optimal conditions were created for the arrival in this world of the highest form of life - the person who was destined to change the face of the planet for a brief moment of its existence (only 500 thousand years - one instant by the standards of geology!) To unrecognizability. And, at the same time, and give the concepts of "life" and "evolution" a completely new meaning ...