An newly-evolved species has a much better chance of surviving for a long time if it first appears right after a mass extinction. University of Cincinnati geologist Arnold Miller has found that the trend holds true no matter what was the ultimate cause of each mass extinction. New species were more widespread and fared better over the long run.
Miller used a database of marine fossils to examine longevity trends throughout the Phanerozoic era of the last 540 million years. In four separate cases, he found that creatures that first appeared following mass extinctions survived for longer periods of time than those that appeared at other times.
He divided the Phanerozoic era into 156 substages and looked at the average longevity of creatures originating in each stage. Significant peaks showed that they thrived following major mass extinctions in the Late Permian, Late Triassic, and Late Cretaceous extinctions--three of the ?big five? extinctions in that period of time. ?These are very sharp peaks,? says Miller.
The pattern does not extend back into the Paleozoic, the earliest of the three eras that comprise the Phanerozoic. Although there were fairly high extinction rates during parts of the Cambrian, Ordovician and Devonian, Miller?s analysis showed no clear relationship between extinction events and longevity in any of those periods. ?To see nothing is quite something,? he says. It?s possible that, after the Paleozoic, there was a major change in the dynamics of evolution, but Miller feels that he doesn?t yet have an explanation for this.
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