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Punctuated evolution.

Since the development of Darwin's notion of evolution by natural selection (see 1858), the general feeling had been that evolution was a slow process but a steady one.

In 1972 this view was challenged by the American paleontologists Stephen Jay Gould and Niles Eldredge, who suggested what they called punctuated evolution.

In this view, species are stable and persist virtually unchanged for a long time. Then, certain small groups of a particular species, subjected for some reason to a special environmental pressure, change comparatively rapidly and develop into a new species. Evolution, then, is a matter of stable situations punctuated by occasional periods of rapid change.

This view has not yet been generally accepted, but it is characteristic of the present-day turmoil in the matter of biological evolution. No biologist of any standing doubts that evolution has taken place, but some facets of the exact mechanism of evolution remain under dispute.

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Author:Asimov, Isaac
Publication:Asimov's Chronology of Science & Discovery, Updated ed.
Article Type:Reference Source
Date:Jan 1, 1994
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