> "On the positive, the earth has been much warmer and much colder" The concern is, during these hotter/colder periods of earth's existence - what happened to

> "On the positive, the earth has been much warmer and much colder" The concern is, during these hotter/colder periods of earth's existence - what happened to life on earth during that time? Did populations decline? Was life nearly run into extinction (dinosaurs, etc)?