Mass Extinctions Reset the Long-Term Pace of Evolution

ScienceDaily (July 2, 2012) —
A new study indicates that mass extinctions affect the pace of
evolution, not just in the immediate aftermath of catastrophe, but for
millions of years to follow. The study's authors, University of
Chicago's Andrew Z. Krug and David Jablonski, will publish their
findings in the August issue of the journal Geology.

Scientists expected to see an evolutionary explosion immediately
following a mass extinction, but Krug and Jablonski's findings go far
beyond that.

"There's some general sense that the event happens, there's some
aftermath and then things return to normal," said Krug, a research
scientist in geophysical sciences at UChicago. But in reality, Krug
said, "Things don't return to what they were before. They operate at a
different pace, sometimes more rapidly, other times more slowly.
Evolutionary rates shift, and that shift is permanent until the next
mass extinction."

Krug and Jablonski's suggestion that the potential for rapid
speciation and expansion of survivors and new groups of organisms in the
"emptier" world following a mass extinction "is a reasonable
possibility as one source of rate change," said paleontologist Richard
Bambach of the Smithsonian Museum of Natural History, who was not
directly involved in the UChicago study.

The long-term evolutionary patterns of species diversification
following mass extinctions are poorly understood. Paleontologists have
extensively debated whether diversity has increased over the last 251
million years, which followed the most devastating mass extinction in
Earth history, Bambach said