BBC: Over the past 450 million years, life on Earth has been devastated by five mass extinction events that are widely recognised by geologists. Now, an international team of researchers proposes adding a sixth mass extinction to the list. The team believes it has accumulated sufficient evidence to promote the Capitanian event to the rank of mass extinction. The extinction occurred approximately 262 million years ago. Their proposal would elevate the Capitanian, which occurred during the Middle Permian...