| theory of, Biology. a hypothesis holding that the evolution of species proceeds in a characteristic pattern of relative stability for long periods of time interspersed with much shorter periods during which many species become extinct and new species emerge. Also called punctuationalism. Compare gradualism (def. 3). |
| punc·tu·at·ed equilibrium (pŭngk'chōō-ā'tĭd) n. The theory that speciation occurs in spurts of major genetic alterations that punctuate long periods of little change. |
The theory that new species evolve suddenly over brief periods of time, followed by longer periods during which there is no genetic change. Punctuated equilibrium is a revision of Darwin's theory of evolution. (Compare gradualism and catastrophism.)