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Institute of Paleobiology, Polish Academy of Sciences, Al. Zwirki i Wigury 93, PL-02-089 Warszawa, Poland; and Lamont-Doherty Geological Observatory, Palisades, NY 10964, USA
The concept of periodic mass extinctions by extraterrestrial impacts has contributed very strongly to the current revival of interest in the problem of mass extinctions. In this context, several radical claims have been made, asserting that the newly emerging picture of mass extinctions as a separate class of biological phenomena, caused by a separate class of processes, demands a far-reaching revision of the the neodarwinian paradigm of evolution and implies a vindication of the Cuvierian perspective on Earth's history. The validity of these claims, however, is questionable at all levels: from the interpretation of particular events, to the concept of mass extinctions as a special class of phenomena, to their proposed causation by impacts, and to their alleged historical pedigree and implications for current evolutionary theory. Mass extinctions may actually be clusters of more or less accidentally aggregated-in-time but causally distinct extinction episodes.
