The last extinction event, 11 million years ago, saw 10 per cent of the Earth’s inhabitants wiped out. This means there is around 16million years until the next event takes place, although the graph shows that it occasionally the event takes place up to 10 million years early. Asteroids crashing into the Earth are commonly believed to be one of the main reasons behind mass extinctions like that suffered by the dinosaurs - the Cretaceous-Tertiary (KT) extinction. The extinction wiped out more than half of all species on the planet clearing the way for mammals to become the dominant species...