Why do some people believe that humans will go extinct?

I believe that at some point and time everything has to go back to zero. Its just inevitable

I think humanity will die because of our destructive and ignorant behavior, of course, this will probably be in a hundred years away.

everything has a beginning and an end

because in 4 years, ie 2012. when the "hope" of "change" never develops...we are going to snap, and obliterate each other
/thread

I think mutation will begin when cloning becomes legal, reproductive organs become screwed up with clones, babies are deformed, and eventually a race of monsters will evolve from us. JMO

Of course we'll become extinct. What makes us special?

Well, if you think about it, this will probably not happen for a wvery long time. We seem to kill off, or "fix" all our mutations, deformations and monsters. We cut off tails, separate twins, remove excess limbes, usable or not. Who sayus these aren't the next steps in our evolution? We probably will end up killing off ourselves by not allowing ourselves to evolve.

Because eventually, a virus is going to evolve that we aren't going to be able to confine. And we are destroying our Earth as we speak, so we are heading down the right path to destruction.