What is the name of the theory that evolution occurs in rapid bursts?

The theory that evolution occurs in rapid bursts separated by long periods of little change is called punctuated equilibrium. It describes evolution as a pattern of relative stability, or stasis, interrupted by comparatively brief episodes of evolutionary change.

Paleontologists Niles Eldredge and Stephen Jay Gould developed the theory and published their landmark paper in 1972. Their idea grew from studying fossils that often appeared nearly unchanged across long geological intervals, followed by the relatively sudden appearance of distinct forms. They connected this pattern especially with speciation in geographically isolated populations.

“Rapid” does not usually mean that a completely new species appears in one generation, and punctuated equilibrium does not reject natural selection or evolution. The bursts may last thousands of years—brief compared with geological time—and the theory focuses chiefly on changes at the species level. It is also not the same as catastrophism, which emphasizes external disasters, or gradualism, which emphasizes slow continuous change. Fossil evidence includes both gradual and punctuated patterns, so evolutionary rates can vary rather than following one universal tempo.