In the last 540 million years, the Earth has experienced five mass extinctions that killed about 50% of animal species. The most famous extinction occurred about 65 million years ago when the dinosaurs disappeared from the face of the Earth.
The Earth, and its inhabitants, have also been hit by many smaller extinctions. Over 97 percent of all species that have ever lived on our planet are extinct today.
Many fossils testify to life on Earth before us, and scientists estimate that in the past 540 million years the Earth has been hit by between five and more than twenty mass extinctions, depending on what criteria are used when one extinction is called "mass".
The "big five" mass extinctions, identified in 1982 by Jack Sepkoski and David M. Raup, are accepted by scientists as the most significant.
1. Ordovician - Silurian extinction, 450 - 440 million years ago
2. Devonian - carbon extinction, 375 - 360 million years ago
3. Permian - Triassic extinction, about 252 million years ago
4. Triassic - Jurassic extinction, 205 - 199 million years ago
5. Cretaceous - Paleogene extinction, about 65 million years ago
6. Mass extinction?
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