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Fossil Records Show Biodiversity Comes And Goes

A detailed and extensive new analysis of the fossil records of marine animals over the past 542 million years has yielded a stunning surprise. Biodiversity appears to rise and fall in mysterious cycles of 62 million years for which science has no satisfactory explanation. The analysis, performed by researchers with the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California at Berkeley, has withstood thorough testing so that confidence in the results is above 99-percent.

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Muller and Rohde have been working on this study for nearly two years, and first discovered the 62 million year biodiversity cycle in November, 2003. They spent the next year trying to either knock it down or explain it. Despite examining 14 possible geophysical and astronomical causes of the cycles, no clear explanation emerged.

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In examining their results, Muller and Rohde found that the fossil diversity cycle is most evident when only short-lived genera (those that survived less than 45 million years) are considered. They also found that some organisms seem to be immune to the cycle, while others are exceptionally sensitive. For example, corals, sponges, arthropods and trilobites follow the cycle, but fish, squid and snails do not. In general, longer-lived genera that are more diverse and widespread stand a better chance of resisting the 62 million year cycle.