random act of nature in any form

our time as a species is limited in the long scale nomater how we look at it... I would even call wiping ourselves out before we reach type one civilization natural to an extent.
if you mean the planet itself?.....
well the moon pulling away will cause alot of problems but wont exactly destroy life, not any worse than any other mass extinction.
now the sun expanding as it enters its red giant phase will wipe out any and all known life.. the planet itself though could be dead or dying at that point anyway as it's geothermal system shuts down and the core cools..
though lets not forget that life can be wiped out for the most part by any random cosmic event, such as a good old gamma burst in any part of the galaxy " granted the burst is aimed our way"
so really there are a billion ways we can go
