...it also pushes the lower bound lower :( really it just means we can extrapolate less from the historical record than had we not evolved, although I suppose that's a rather silly statement to make given that it was "non-intelligent" life that produced us in the only sample we have.

Now I'm actually morbidly curious: do you think humans could even come close to sterilizing this planet if we wanted to? I mean maybe we could burn away the atmosphere if we set off enough nukes (probably more than humanity's ready-to-use-stockpile, I think?), but the biomass that's inside the ocean (...would that even remain without an atmosphere or would it boil off? regardless...) and crust is simply massive. I strongly suspect that life would keep on going.