Two-and-a-half billion years ago, the earth was a very different place, but it already had life. Not anything you’d recognize, or could even see, but life of a sort anyway. While those archaic single-cell life forms reproduced by splitting, they also managed to mutate like crazy, at least on an evolutionary scale. And some of them caused a mass extinction event.
It’s kind of strange to think that oxygen could have ever been considered a pollutant in the air. But it was, and that affected everything that came after. You have to wonder what kind of life forms will evolve in the greenhouse gas-rich atmosphere that will remain after we become extinct after the climate change apocalypse. -via Digg