Punctuated Equilibrium
A theory in evolutionary biology that once species appear in the fossil record the population will become stable, showing little evolutionary change for most of its geological history, save for periodic eras of massive change and diversity.
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Origin
Paleontologists Niles Eldredge and Stephen Jay Gould first presented the theory at a 1971 meeting of the Geological Society of America and published it in their 1972 paper "Punctuated Equilibria: An Alternative to Phyletic Gradualism." Drawing on Eldredge's trilobite research and Gould's studies of land snails, they challenged the Darwinian assumption of slow, steady evolutionary change, arguing instead that species remain stable for long periods and change rapidly during short bursts of speciation.
Updated February 22, 2026