Are Mass Extinctions Cyclical? 

THIS ARTICLE based on THIS ACADEMIC JOURNAL ARTICLE reports that mass extinctions follow a cycle of about 27 million years. And they are associated with major asteroid impacts and devastating volcanic eruptions. But what controls the cyclicity remains unknown. 

Explain that convincingly and your reputation is made!

Much of the groundwork for the academic paper is based on Mike Benton's work. But it goes into statistical analysis which flies a considerable distance above my head. But they come out of this convinced of the 27.5 My. periodicity.

An illustration - only glancingly relevant to the article but more interesting than the statistical graphs