by mass extinctions 'every 27m years'
Life on Earth suffers catastrophic
extinctions every 27 million years,
according to researchers.
By Tom Chivers
Published: 3:30PM BST 12 Jul 2010
For at least the last 500 million years, say
Adrian Melott, an astrophysicist at the
University of Kansas, and Richard Bambach, a
palaeontologist at the Smithsonian
Institute, there has been a burst of
extinctions every 27 million years.