Is it really possible? Perhaps it's a failure of imagination but the only things I can think of that would guarantee human extinction are impacts from massive a

Is it really possible? Perhaps it's a failure of imagination but the only things I can think of that would guarantee human extinction are impacts from massive asteroids or nearby gamma ray burst or supernova. There are two billion poor subsistence farmers largely disconnected from market economies who aren't dependent on modern technology so the likelihood of them getting completely wiped out is very remote.