So very rare. Mass extinctions, from your number, appear to be a once in a 132 Mya event. [0] Humans have been on Earth 0.1 Mya, 0.2Mya; statistically we'll b

So very rare. Mass extinctions, from your number, appear to be a once in a 132 Mya event. [0] Humans have been on Earth 0.1 Mya, 0.2Mya; statistically we'll be around for a total of 0.2 to 0.4 Mya in total. [0][1] Therefore, there is a 1-330 chance of the two time lines overlapping. [0] Assuming the present time is random, I believe the best estimate of event frequency is that we're in the middle of two occurrences; hence the doubling. [1]I'm being generous here. I don't think we have 0.2 Mya left in us, primarily because for the first time in history we have the ability to kill ourselves off. Therefore the assumption that out present in at a random position of the human experience used in [0] is invalid. Since we probably only have 100 years left, that's a 1-1E6 possibility facing us.