At least five times (six if you count the present day extinctions) during the history of life on Earth, there have been mass extinctions which have wiped out numerous species. The scale of these mass extinctions are hard to comprehend. to wipe out a species, a mass extinction would have to kill all the breeding individuals of that species. Yet when we look back in the past, we find that each of the mass extinction wiped out more than 50% of species, and the most devastating (the Permian-Triassic event) wiped out an estimated 96% of marine species, and 70% of land species.
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