Viruses polluted themselves to death when they decided that Oxygen wasn't a dangerous by-product that came out of their factories. Conservative groups didn't care about the poor single-cells on a fixed income and so naturally those poor cells where the first to perish once doomsday happened and huge elders crawled from the seas to destroy the unbelievers who lived in a palace of tortured glass, served by legions of monsters forged from the tears of the undead, and each one clad in armor carved from the concentrated suffering of grieving mothers. The survivors reside within all mankind, waiting for the thin glass wall within them to crack, so that the skeleton within may take over... Remove the ability to feel... anything but pain. Once the senseless eyes have been removed, the soul is removed. The living husk is testament to eternal cruelty.
http://www.universetoday.com/1002/how-did-early-bacteria-survive-poisonous-oxygen/http://io9.com/5502298/new-ancient-way-of-making-oxygen-discoveredhttp://www.sciencedaily.com/releases/2008/04/080401200449.htm