That would be 10 extinctions per 10,000 species per year, or 1,000 times the background extinction
Currently evolutionary theory is based almost exclusively on pattersn of background extinctions
, Jablonski says; scientists have assumed that mass extinctions simply accelerate or emphasize trends of background extinctions
so that the same kinds of organisms are wiped out by a mass extinction, only in much greater numbers.
Both background extinctions
, which represent most extinctions in the history of life, and mass extinctions tend to be clumped into particular evolutionary lineages," Jablonski said.
So too does the author find Gould's accent on the caprice of mass extinctions "very plausible," along with its implied, attendant claim that such calamities are qualitatively distinct from run-of-the-mill background extinctions