Modeling Modes of Evolution: Comparing Phyletic Gradualism & Punctuated Equilibrium

Abstract

Introduction Paleontologists have discovered two major patterns in life that make it difficult to support a totally uniformitarian view of life's development (Benton 1993, p. 100). These two views are known as phyletic and punctuated equilibrium. Phyletic gradualism is the traditional Darwinian view that an interminable number of intermediate forms have existed, linking together all species in each group by gradations as fine as our existing varieties (Darwin 1975). Punctuated equilibrium, developed by Niles Eldredge and Stephen Jay Gould (1972), offers a contrasting view that organic evolution is not steady and regular but episodic and jerky, with long periods of small changes interspersed with rapid bursts of large-scale transformation of species. The latter pattern explains that the gaps in the fossil record are not simply missing data that will show up some day-as maintained by gradualists-but are real and must be interpreted as such.