NUCLEAR WAR!
USA vs RUSSIA

Zombie Invasion. I've been saying for years, it's coming, be warned.

- Me when they stop making beer.

- Religions also.

Wii Fit

Agreed.

Allowing women to control the world. We were close with Hillary, luckily Obama came along. :)

For realz. We will be our own downfall. Life in itself will never leave Earth until the sun expands and devours it.

Wait until Herpes Simplex mutates into something that can kill. Such a high percentage of the population has it, so it has a strong infrastructure. (Joke)

I do think a virus will do us in if anything, or at least change our lifestyle of living in large communities.

Life will always exist on Earth in some form. Considering the unlikely places trees sometimes sprout (cracks in concrete and ashphalt), I think cities will be recolonized by forests within a couple of hundred years.

jesus

Human life I would say would either end by means of either an extremely potent virus, OR perhaps terrorists with nuclear weapons, or a theocracy with nunclear weapons.

All life will end when the earth does most likely.

I would have to say that the main cause of killing off all life on Earth will be the same as it's always been: death. It has a 100% success rate so far, after all.

Oh, you wanted a cause of death? Why pick one when there's so many options to choose from?