Running Away from Mass Extinction
Species extinction is a natural process which has occurred since the beginning of life 3.8 billion years ago. In the past, there were five large scale extinction which were especially threatening for life on the blue planet. Those extinctions were caused by change in ocean chemistry, volcanic activity, climate change and asteroid impacts. In some cases entire families and orders were wiped out of the Earth surface. The worst mass extinction was the Permian Triassic, about 250 million years ago, when 90% of the species disappeared. At this point, life was very close to end.