information:highlighting, structural:expansion
Punctuated equilibrium

Early in his career, Gould and his colleague Niles Eldredge developed the theory of punctuated equilibrium, which describes the rate of speciation in the fossil record as occurring relatively rapidly, which then alternates to a longer period of evolutionary stability. It was Gould who coined the term "punctuated equilibria" though the theory was originally presented by Eldredge in his doctoral dissertation on Devonian trilobites and his article published the previous year on allopatric speciation.

According to Gould, punctuated equilibrium revised a key pillar "in the central logic of Darwinian theory." Some evolutionary biologists have argued that while punctuated equilibrium was "of great interest to biology generally," it merely modified neo-Darwinism in a manner that was fully compatible with what had been known before. Other biologists emphasize the theoretical novelty of punctuated equilibrium, and argued that evolutionary stasis had been "unexpected by most evolutionary biologists" and "had a major impact on paleontology and evolutionary biology."

Comparisons were made to George Gaylord Simpson 's work in Tempo and Mode in Evolution (1941), in which he also illustrated relatively sudden changes along evolutionary lines. Simpson describes the paleontological record as being characterized by predominantly gradual change (which he termed horotely), although he also documented examples of slow (bradytely), and rapid (tachytely) rates of evolution. Punctuated equilibrium and phyletic gradualism are not mutually exclusive (as Simpson's work demonstrates), and examples of each have been documented in different lineages. The debate between these two models is often misunderstood by non-scientists, and according to Richard Dawkins has been oversold by the media. Some critics jokingly referred to the theory of punctuated equilibrium as "evolution by jerks", which prompted Gould to describe phyletic gradualism as "evolution by creeps."