I saw this on another forum and found it intriguing as to what some people had to say.
What do you believe will mean the end of civilization? I mean, the Paleozoic Era was marked by the mass extinction of 95% of all living organisms 245 million years ago, the end of the Mesozoic Era was the mass-extinction of all the Dinosaurs 66.4 million years ago, so what will cause the end of the Cenozoic (or present) era in a world where homo sapiens reign supreme? And when do you believe it will happen?
(Mind the eras and earth's history stuff, I just got finished studying for my Earth Systems exam. )