• More than half of all life on the earth has been wiped out, repeatedly, in mass extinctions over the past 500 million years.
  • One such disaster, which included the dinosaurs' disappearance, is widely attributed to an asteroid impact, but others remain inadequately explained.
  • New fossil and geochemical evidence points to a shocking environmental mechanism for the largest of the ancient mass extinctions and possibly several more: an oxygen-depleted ocean spewing poisonous gas as a result of global warming.