Punctuated Equilibrium

The theory known as 'Punctuated Equilibrium' was originated by the paleontologists Stephen Gould and Niles Eldridge in their paper Punctuated Equilibria: An Alternative to Phyletic Gradualism because the fossil record did not show evidence for Darwin's original theory of phyletic gradualism, gradualistic evolution, and only showed steady microevolution in the fossil record for long periods, then sudden emergence of brand new species as though suddenly created. Today Punctuated Equilibrium is the predominant theory on Evolution. "Still, if evolution is gradual, there should be a fossilized record of small, incremental changes on the way to a new species. But in many cases, scientists have been unable to find most of these intermediate forms. Darwin himself was shaken by their absence. His conclusion was that the fossil record lacked these transitional stages, because it was so incomplete. That is certainly true in many cases, because the chances of each of those critical changing forms having been preserved as fossils are small. But in 1972, evolutionary scientists Stephen Jay Gould and Niles Eldredge proposed another explanation which they called 'punctuated equilibrium.' That is, species are generally stable, changing little for millions of years. This leisurely pace is 'punctuated' by a rapid burst of change that results in a new species and that leaves few fossils behind." -Prentice-Hall on PBS

Gradualism
The morphological discontinuity and the geologic time scales involved (i.e decades or hundreds of years instead of thousands or millions) puts Punctuated Equilibrium in direct contrast with Gradualism; essentially an acknowledgement that species appeared suddenly in advanced stages without the gradual transitions required for a common ancestor. The lack of transitional forms in the fossil record troubled Darwin himself, who tried to explain it through the then-incomplete knowledge of the fossil record.

Falsifiability
The Biotic Message: Evolution Versus Message Theory by Walter ReMine accuses Punctuated Equilibrium of being unfalsifiable, of simply creating an unsubstantiated hypothesis to explain away the growing body of evidence seen from the fossil record that evolution is not constant and gradual, and that transitional forms don't exist. "So is punctuated equilibrium testable? Gould says that a series of fossils showing gradual development of an adaptation would refute punctuated equilibrium. ReMine points out the 'no lose' situation that Gould and company have created here: if the fossils show systematic gaps, then the punctuated equilibrium model of evolution is 'proven', but if the fossils show gradualism, then the standard neo-Darwinian model of evolution is proven. In other words, evolution itself is no longer falsifiable! Punctuated equilibrium and neoDarwinism are both now part of the evolutionists' grab-bag of conflicting theories as Gould and Eldredge now view punctuated equilibrium as an addition to evolutionary theory rather than an alternative." -Don Batten, review of "The Biotic Message" in Creation