http://www.talkorigins.org/faqs/punc-eq.html Punctuated Equilibria Copyright � 1996-1997 by Wesley Elsberry [Last Update: February 4, 1996]
Outline 0. Foreword 1. Summary of Punctuated Equilibria 2. The problem of paleospecies 3. Patterns of speciation from neontological study 4. Application of neontology to paleontology 5. PE vs. Phyletic Gradualism 6. Common errors in discussion of PE 7. References 8. Acknowledgements 0. Foreword There are few components of modern evolutionary theory which seem so prone to misinterpretation as Niles Eldredge and Stephen Jay Gould's theory of punctuated equilibria (PE for short). In this matter, the person attempting to come to a better understanding of punctuated equilibria will find that he or she may be hampered by the popular writings of those same authors rather than helped. As in most cases, the primary literature remains the best source of information. 1. Summary of Punctuated Equilibria The essential features that make up Punctuated Equilibria are as follows: - Paleontology should be informed by neontology. - Most speciation is cladogenesis rather than anagenesis. - Most speciation occurs via peripatric speciation. - Large, widespread species usually change slowly, if at all, during their time of residence. - Daughter species usually develop in a geographically limited region. - Daughter species usually develop in a stratigraphically limited extent, which is small in relation to total residence time of the species. - Sampling of the fossil record will reveal a pattern of most species in stasis, with abrupt appearance of newly derived species being a consequence of ecological succession and dispersion. - Adaptive change in lineages occurs mostly during periods of speciation. - Trends in adaptation occur mostly through the mechanism of species selection. The theory of Punctuated Equilibria provides paleontologists with an explanation for the patterns which they find in the fossil record. This pattern includes the characteristically abrupt appearance of new species, the relative stability of morphology in widespread species, the distribution of transitional fossils when those are found, the apparent differences in morphology between ancestral and daughter species, and the pattern of extinction of species. PE relies upon the insights of study of modern species for its principles. These studies indicate the importance of consideration of geography and interspecies interactions upon predictions of the distribution and abundance of transitional specimens. While Eldredge and Gould acknowledge that geological processes contribute to the "gappiness" of the fossil record, they also assert that PE is by far the more important consideration in that regard. --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] Visit IAGI Website: http://iagi.or.id IAGI-net Archive 1: http://www.mail-archive.com/iagi-net%40iagi.or.id/ IAGI-net Archive 2: http://groups.yahoo.com/group/iagi Komisi Sedimentologi (FOSI) : F. Hasan Sidi([EMAIL PROTECTED])-http://fosi.iagi.or.id Komisi SDM/Pendidikan : Edy Sunardi([EMAIL PROTECTED]) Komisi Karst : Hanang Samodra([EMAIL PROTECTED]) Komisi Sertifikasi : M. Suryowibowo([EMAIL PROTECTED]) Komisi OTODA : Ridwan Djamaluddin([EMAIL PROTECTED] atau [EMAIL PROTECTED]), Arif Zardi Dahlius([EMAIL PROTECTED]) Komisi Database Geologi : Aria A. Mulhadiono([EMAIL PROTECTED]) ---------------------------------------------------------------------
