@grumpybozo @mjd @licho @samim Aquatic life was thriving before that since UV can't penetrate water very deeply. In the beginning, the production of oxygen by those nasty photosynthetic cyanobacteria was a huge global ecological catastrophe, since oxygen is a deadly poison to many bacteria. But then, life evolved to take advantage of all the oxygen, and soon organisms began to multiply that couldn't even live without.