Reply #100: NEVER. GONNA. HAPPEN.

[Xithras]

Species are biologically viable down to a few thousand reproductive members (possibly even lower, but deformities caused by inbreeding becomes an issue with fewer than that).

There are 6.4 BILLION humans on the Earth. Even if you eliminate 99.99% of the humans on Earth, you're left with more than a half million of us...more than enough to repopulate the entire planet within a few thousand years.

As for those predicting an end of oxygen or a 140 degree planet...we'll, it just isn't going to happen. The oceans are the great moderator, and they prevent our planet from getting that hot. If the average temp gets too high, oceanic evaporation will cause a cloud blanket over the planet, cooling it and preventing it from warming further. The northern climes will see another ice age and the rest of the planet will become tropical rain forest, but our species has survived ice ages before and half the population on Earth today lives in the tropics, so the weather won't kill us.

In reality, the human species is so pervasive and so adaptable that only four things could lead to our extinction: 1) A lethal pathogen could wipe us out 2) Full nuclear winter, caused by war or an asteroid strike 3) Our sun FUBARing and causing us to cook or freeze (astronomical observation suggest that it CAN happen) 4) Nearby supernova or gamma ray burst sterilizes the planet.

We can survive everything else.