Extinction of widespread species is common in evolutionary time (millions of years) but rare in ecological time (hundreds or thousands of years). In the fossil record, there appears to be a smooth continuum between background and mass extinction; and the clustering of extinctions at mass extinctions cannot be explained by the chance coincidence of independent events. Although some extinction is selective, much is apparently random in that survivors have no recognizable superiority over victims. Extinction certainly plays an important role in evolution, but whether it is constructive or destructive has not yet been determined.
David Raup is the Sewell L. Avery Distinguished Service Professor in Geophysics, Evolutionary Biology, Conceptual Foundations of Science, University of Chicago. He is a Member of the National Academy of Sciences, US, and was President of the Paleontological Society, 1976. He has written numerous articles on paleobiology and evolutionary biology.
* Geophysical Sciences, University of Chicago, 5734 South Ellis Avenue, Chicago, IL 60637, USA.