A statistical analysis of the rates of extinction and origination in the fossil record shows that life seldom rebounds rapidly from an extinction.
The results imply that the diversification of life obeys "speed limits" set by evolutionary processes, said study author James Kirchner, professor of earth and planetary science at UC Berkeley.
"There seem to be biological mechanisms that limit diversification of new organisms and control which ones become successful enough to persist," he said. "Biodiversity is slow to recover after an extinction."
This apparent speed limit on the rate at which surviving organisms evolve and diversify has major implications for present-day extinctions.
"If we substantially diminish biodiversity on Earth, we can't expect the biosphere to just bounce back. It doesn't do that. The process of diversification is too slow," Kirchner said. "The planet would be biologically depleted for millions of years, with consequences extending not only beyond the lives of our children's children, but beyond the likely lifespan of the entire human species."
The paper by Kirchner appears in the Jan. 3, 2002, issue of the journal Nature.
Kirchner has been mining a fossil database created by the late University of Chicago paleontologist Jack Sepkoski, who catalogued the genera and families of fossil marine animals over the past 530 million years, from the Cambrian to the present. Using a technique called spectral analysis, Kirchner has looked for patterns in the rates at which new organisms appear or disappear.
Last year Kirchner and colleague Anne Weil reported that the Earth needs, on average, about 10 mill
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Contact: Robert Sanders
rls@pa.urel.berkeley.edu
510-643-6998
University of California - Berkeley
2-Jan-2002