ISS Expedition 7 Crew, EOL, NASA
(Image record from Gateway to Astronaut Photography of Earth)

Since its formation, the Earth has gone through several stages in which life has progressively evolved. To understand the magnitude of time of these changes, imagine that the entire history of the Earth was condensed into one year. During January and February, the Earth went through a period of high temperatures which gradually decreased. After chilling, by early March the first primitive single-celled organisms appeared and these were the sole living beings for five months (i.e., 2100 million years). In July the first bacteria and other organisms without nuclei appeared, and life continued with no major complications for three more months (1900 million years). In November, the first molluscs, arthropods, corals, fish and land plants (licopodios, horsetails and ferns) appeared. During the first weeks of December appeared the amphibians and reptiles, while birds and mammals appeared in the last week of December. The first hint of man was on the last day of December, and his civilization only developed in the final minutes of the last day of the year.