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The dinosaurs
Often I look for informations about what the Earth was like millions of years ago, and about how life has evolved up to man. I find it very interesting. Now I’m writing something about the history of dinosaurs, and about its relationship with mammals’ evolution. Corrections are welcome.
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About 220 millions of years ago, the first dinosaurs began to appear on the Earth. They were reptilians that evolved more than others and became able to stand up on their toes. Since on the Earth there wasn’t any stronger species at that time, over the millennia the dinosaurs evolved and differentiated at a relatively fast rate. Through the fossils that have been found here and there around the world, a big variety of dinosaurs’ species have been discovered. Some of them were very big. The largest one weighed as much as ten elephants!! Since they were very exposed to predation by dinosaurs, mammals evolved at a quite slow rate during the dinosaurs’ era. Up to 65 millions of years ago, they were mostly tiny mouse-like animals that lived on trees and fed themselves with insects.
65 millions of years ago the Earth must have been struck by a catastrophic event that annihilated almost all the dinosaurs, because after that time there is no longer evidence of them populating the Earth. Various hypotesis have been made, the most common asserts that a big asteroid impacted the Earth. As a consequence of that impact, the air became polluted to such an extent that all terrestrial dinosaurs died. Only those who were able to fly survived, the ancestors of the current birds.
After the dinosaurs disappaered, mammals became much less exposed to predation, and they began to evolve and differentiate at a much faster rate. A large variety of species began to spread all over the world. In particular, the mouse-like animals that lived on the trees evoluted first into monkeys, then into hominids, and finally into the current man. Weren’t the dinosaurs killed by an asteroid or by a similar event 65 millions of years ago, we surely wouldn’t be there.
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