99% Of life died a billion years before dinosaurs because of mass-extinction

Scientists at Stanford University have uncovered evidence that 99% Of life died a billion years before dinosaurs because of mass extinction. Clues suggest that two billion years ago there would have been just single-celled organisms around. The research stated it as "feast and famine" as long before there were complex life forms on Earth. 2.4 billion years ago, the Earth's atmosphere had low levels of oxygen.