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This article deals with the processes of the evolution of life. For evolutionary thought, see History of evolutionary thought. The history of life on Earth tells the processes by which living organisms have evolved, from the origin of life on Earth some 4.4 billion years ago[1] to the great diversity present in today's organisms. In the same way, it deals with how environmental aspects, in the form of global catastrophes, climatic changes or unions and separations of continents and oceans, have conditioned its development. The similarities between all living organisms indicate the existence of a universal common ancestor from which all known species have diverged through evolutionary processes.[2] Background Edit After the Big Bang, the universe did not meet the conditions for the formation of the life, for this it was necessary for a certain time to pass and certain phenomena to happen. In the earliest moments of the universe the only existing elements were hydrogen and helium, but life requires a great diversity of elements. These first elements accumulated forming stars, which after their collapse as a supernova gave rise to the rest of the elements necessary for the formation of biomolecules. Once these elements were created, life was still not possible until planets were formed by accretion that contained this diversity of elements. The minimum time for these phenomena to occur - that is, for the cycle of a generation of stars to end and after that planets are formed with the remains of the supernova - is no less than 4,000 million years. [3] The dominant organisms of life in the Early Archean were bacteria and archaea, which coexisted to form microbial mats (also known as "mats" or "microbial mats") and stromatolites. Many of the most important events in early evolution are believed to have taken place within them.[4] The evolution of oxygenic photosynthesis, around 3.5 billion years ago, led to the oxygenation of the atmosphere, which began around 2.4 billion years ago.[5] The earliest evidence of eukaryotes (complex cells with organelles), dates to 2.2 billion years ago,[6] and while they may have been present earlier, their accelerated diversification began when they began to use oxygen in their metabolism. Later, around 1.7 billion years ago, multicellular organisms began to appear, with cellular differentiation each cell in the organism began to perform specialized functions.[7] The first land plants date to around 450 million years ago,[8 ] although evidence suggests that algae scum formed on land as early as 1.2 billion years ago. Land plants were so successful that they are believed to have contributed to the Late Devonian extinction.[9] Invertebrate animals appear during the Ediacaran period,[10] while vertebrates originated around 525 million years ago during the Cambrian explosion.[11] During the Permian period, synapsids, which included the ancestors of mammals, dominated the earth[12] but the Permian-Triassic extinction event 2