Punctuated equilibrium is a theory in evolutionary biology that suggests species experience long periods of stability, or equilibrium, interrupted by brief, rapid changes. This means that most evolutionary changes occur in relatively short bursts, often due to environmental shifts or other factors, rather than gradually over time. The concept was introduced by paleontologists Niles Eldredge and Stephen Jay Gould in 1972. They proposed that the fossil record shows these sudden changes, challenging the traditional view of gradual evolution. This theory helps explain the patterns observed in the fossil record, where species appear and disappear relatively quickly compared to the long periods of stability.