The oceans were the cradle of life on Earth for billions of years before our ancestors took to the land and air. But they have also seen some of the most devastating mass extinctions in geological history. In this month's Naked Oceans we find out about the bizarre evolutionary experiments that appear in the first explosions of complex life over 600 million years ago, and what may have driven the catastrophic End Permian extinction event, and how it could teach us about potential future ocean extinctions. Plus we ask another marine expert to choose our Critter of the Month...