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contents   Biology Articles » Evolutionary Biology » The role of
extinction in evolution » Causes of Extinction  Causes of
Extinction - The role of extinction in evolution  A remarkable
feature of the history of life is that so many successful
species have died out. Many of the extinctions recorded in the
fossil record are of species or large groups of species that
were ecologically tolerant and occurred in great numbers in all
parts of the world. If these extinctions were caused by slow
declines over long periods of time, as Darwin thought, they
might be explicable in terms of the cumulative effect of very
slight deficiencies or disadvantages. But it is becoming
increasingly clear that successful species often die out
quickly. This is best documented for the K-T mass extinction
because of the extensive field work inspired by the controversy
over the cause of that event. Several important biologic groups,
including the ammonites and dinosaurs, now appea