"Mass extinction theory on the rocks" (2005)

Mass extinction theory on the rocks

A MYSTERIOUS pattern of apparent mass extinctions in the marine fossil record is in fact nothing of the kind.

In 2003, Robert Rohde and Richard Muller of the Lawrence Berkeley National Laboratory at the University of California, Berkeley, discovered a clear "boom and bust" cycle in the fossil record of marine organisms. Every 62 million years for the past 542 million years - the Phanerozoic eon - there appears to have been an unexplained mass extinction.

Researchers have considered all kinds of processes to explain the events, including volcanic activity and comet impacts. Now Andrew Smith and Alistair McGowan from the Natural History Museum in London have suggested that the cycles are mere reflections of the amount of rock of different ages that is available for fossil sampling (Biology Letters, DOI:10.1098/rsbl.2005.0345).

"The amount of rock area available for palaeontologists to study could be as important as any biological processes in generating observed changes in diversity," says McGowan. "Systematic changes in the quality of the fossil record could be generated by sea levels rising and falling over millions of years."