Why do you think that? Even a full scale nuclear war would not erase all of humanity, and compared of the past right now is the least likely of all time periods for major disasters like that to happen.
I can't think of anything that could happen right now that would wipe out all of humanity. Even a massive asteroid wouldn't.
(Note: I mean _all_, lots of disasters could of course affect many people in various places.)
We might get a nanotech grey goo scenario, or just a sufficiently bad nanotech disaster to kill off higher life forms.
Plausibly, the parent post meant erase modern civilization rather than every last homo sapiens. Full scale nuclear war could do that. So could an an engineered superflu. Both are a lot more likely than an asteroid strike.
If we can last until we get off the planet, our long term prospects are a lot brighter.
I can't think of anything that could happen right now that would wipe out all of humanity. Even a massive asteroid wouldn't.
(Note: I mean _all_, lots of disasters could of course affect many people in various places.)