| abstract
| - Punctuated equilibrium or Punc Eq is a hypothesis about rates of evolution that was developed by Niles Eldredge and Stephen Jay Gould in 1972. The traditional view was that evolution is a gradual process, driven by the slow accumulation of selected mutations. However, many fossil species did not seem to change very much from their first appearance to their last appearance. That was often explained away as an artifact of poor preservation of fossils, but there were sometimes too many fossils for lack of change to be explained away by that means. Eldredge and Gould decided that this fossil-record stasis was real, and they even had some ideas on what makes it happen. They worked from Ernst Mayr's conception of allopatric speciation, in which a new species forms in a small population that had gotten separated from a larger population. They proposed that this process happens relatively quickly by geological standards, meaning that we seldom get to find intermediate forms between species. After that, if the new species survives and becomes populous, it does not change much in fossilizable features. Punc eq has provoked considerable controversy, though much of the controversy nowadays is about how common stasis is. Punc eq has often been misunderstood as a theory of evolution of new species in one generation, but many advocates propose that it usually takes several thousand generations for a new species to emerge. This is not very fast in geological terms, but a lot more than one generation. Creationists often try to exploit punc eq to "prove" that species were created separately. But what they would get from it is a poof-poof-poof-poof-poof of species creations over geological time, like what many early to mid 19th cy. biologists believed and what Hugh Ross believes. That is, Old Earth Creationism and not Young Earth Creationism. Even worse, each new species poofed into existence would not be very much different from some earlier species and it would usually live in a location closer to where the earlier species lived.
- Punctuated equilibrium is commonly contrasted against the theory of phyletic gradualism, which states that evolution generally occurs uniformly and by the steady and gradual transformation of whole lineages (anagenesis). In this view, evolution is seen as generally smooth and continuous. In 1972, paleontologists Niles Eldredge and Stephen Jay Gould published a landmark paper developing this theory and called it punctuated equilibria. Their paper was built upon Ernst Mayr's theory of geographic speciation, I. Michael Lerner's theories of developmental and genetic homeostasis, as well as their own empirical research. Eldredge and Gould proposed that the degree of gradualism commonly attributed to Charles Darwin was virtually nonexistent in the fossil record, and that stasis dominates the history of most fossil species.
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