The earth was formed 4.543 million years ago. Shortly after, about 4.5 billion years ago, the planet collided with another large body, called Tea; our satellite, to the Moonhas its origin in that collision.
This article has exactly 4543 characters —not counting spaces—, not one more. In other words, if, in relative terms, the beginning of the article coincides with that of our planet, each letter, number and punctuation mark that you are reading is equivalent to a million years. And 438 have already passed.
At this moment, the surface of our planet, previously incandescent and covered with lava, has already cooled, the oceans have appeared, and molecules are seething in the water that, undergoing a very primitive selective pressure, associate with each other. until the first forms of life emerged. It is not very clear when exactly they arose, it could have been about 3.8 billion years ago, that is, right now in the text. Perhaps it took longer, while biochemical dynamics took the step towards biological evolutionand these biomolecules organized themselves until they were capable of replicating themselves, thus ending the formation of life, about 3.5 billion years ago, that is, at this point in the text, approximately.
What we do know is that one of the first functions that life acquired was photosynthesis. The atmosphere before life was reducing, with abundant carbon dioxide; the first photosynthetic microorganisms they began to obtain that carbon as a nutrient. But it was anoxygenic photosynthesis, that is, it did not produce oxygen in return.
For a long time the conditions were maintained. But millions of centuries later, something changed. If the history of evolution has taught us anything, it is that life cannot be contained, it expands and breaks through barriers. This is how new ways of photosynthesis proved to be more apt than the old ones. And as so often happens in the history of the earth, life makes its way.
oxygenic photosynthesisappears about 2.8 billion years ago—right now, in the text. At first there are a few organisms that go unnoticed among the enormous microbial richness of the planet. But thanks to their great evolutionary advantage, they do not take long to establish themselves as the dominant life form. These organisms expelled oxygen as waste, and over the eons, the air was gradually but constantly transformed.
About 2.45 billion years ago the atmosphere began to change, until it was so oxidizing that it became toxic. This time is known as the oxygen crisis. Respiration soon emerged as a new evolutionary advantage more efficient than fermentation. But the change in the atmosphere produced a loss of the greenhouse effect, and with it, a great ice age that lasted for millions of centuries, until about 2.1 billion years ago.
The gases emitted by volcanism put an end to the ice age, and a tropical climate was installed throughout the planet. Life, almost extinct, flourished again. They began to develop colonial microorganisms; They were not true multicellular life forms, since they only associated with each other, but without reaching the level of differentiation of work. However, a new evolutionary advantage it was about to happen, that it was going to transform the biosphere, and with it, the entire planet.
Thanks to a process called symbiogenesis, some organisms began to associate with others; From these associations a new structure emerged: the cell nucleus. We are about 1500 million years ago. The first eukaryotic cells were not capable of breathing, they still retained that form of fermentation of yesteryear. But thanks to symbiogenesis, through which small prokaryotic cells become part of other larger eukaryotes, the mitochondria, the organelles responsible for respiration. The same mechanism produced the chloroplasts, giving rise to the first algae. Initially, all these organisms, all living beings on the planet were still unicellular. But the scenario was about to change.
About 1 billion years ago, unicellular eukaryotic organisms began to associate in colonies, and just 100 million years later, the first truly multicellular beings began to diversify. The first multicellular algae and the ancestors of animals, also multicellular, independently, began to populate the seas. Several intermittent glaciations and tectonic movements drastically transformed the map, and just 600 million years ago the ediacara faunapopulated the earth, but was replaced by the great cambrian radiationwhich ended about 500 million years ago.
Since then, a total of five mass extinctions have shaken life, and after them, it has always managed to recover. Living beings came out of the water and colonized the mainland. Fungi diversified, then plants —of which today we have their carbon—… and among animals, reptiles arose, increasingly dominant. The dinosaursruled the earth for almost 150 million years, although only a small group, the birds, survived the famous extinction that occurred 66 million years ago. And humanity? 300,000 years ago, at the last pixel of this endpoint.
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