1.75 Billion years ago, cyanobacteria started the "Great Oxygenation Event", making life on Earth possible. (As just reported in
Nature magazine).
"As reported in a new study, scientists have found the oldest direct evidence of oxygenic photosynthetic structures—ones capable of turning sunlight, water and carbon dioxide into energy and oxygen—inside fossilized bacteria from Australia and Canada. The fossils are 1.75 billion years old, pushing back the undisputed origin of photosynthesis as we know it by at least 1.2 billion years. This key process helped life along by pumping the atmosphere full of oxygen."
--Nature
So cyanobacteria aren't ALL bad. Today, they still oxygenate the air we breathe.
Now I'm wondering if ancient flora started the production of fossilized fuels.