MACROEVOLUTION - punctuated by periods of rapid...

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MACROEVOLUTION: TEMPO AND MODE. II Niles Eldredge and Steven Gould stirred up the mud of Tempo and Mode in Evolution with their paper in 1972 on so-called "punctuated equilibrium". The traditional view of evolution was one of phyletic gradualism . This encompassed slow, gradual change in phenotype and speciation by gradual change from one species into another. The alternative - punctuated equilibrium was put forward as a means of accounting for the ever present "gaps" in the fossil record (see figs. 20.4-20.5, pp. 561-562). Eldredge and Gould argued that the gaps were not artifacts of incomplete representation, but that there were essentially no intermediate forms. The general notion is that long periods of stasis or morphological equilibria are
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Unformatted text preview: punctuated by periods of rapid morphological change. This issue was a bit of a blow to the traditional "Darwinian" approach to evolution which largely focused on slow gradual change. This affiliation with "non-Darwinian" evolution is misguided and mislabeled because the original and updated versions of punctuated equilibrium invoked speciation in small isolated populations which fits squarely with Mayr's peripatric model of speciation. Moreover, Darwin described in the Origin of Species a pattern that is entirely consistent with stasis; Darwin did believe that the evolution of complex adaptations was gradual (the eye was built adaptively from preexisting parts in ancestors and did not pop into being quickly in evolutionary time)....
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