11 months ago
Last edited at 11:23AM on 1/23/2013
By running surface samples of the earth and studying the fossils in each layer it has been found there have been extinction spikes approximately every 26 million years. There has been life on this planet for at least 2 billion years. So based on this admittedly sparse evidence 2 billion / 26 million gives a quotient of 76.9. This is of course based on extremely rough estimates, and the results are obviously crude. But our current level of knowledge would put that figure at about 77 times. By the way, the last mass extinction was about 13 million years ago. So if those numbers hold true we have about another 13 million years to go. If this is a multiple choice question from school and the choices are those you gave, I would go with 100 since it is the closest option to my calculated estimation of roughly 77.