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In evolutionary biology, punctuated equilibrium (also called punctuated equilibria) is a theory that proposes that once a species appears in the fossil record, the population will become stable, showing little evolutionary change for most of its geological history. [1]
Eldredge and Stephen Jay Gould proposed punctuated equilibria in 1972. Punctuated equilibrium is a refinement to evolutionary theory. It describes patterns of descent taking place in "fits and starts" separated by long periods of stability. Eldredge went on to develop a hierarchical vision of evolutionary and ecological systems. Around this ...
The theory of punctuated equilibrium developed by Stephen Jay Gould and Niles Eldredge and first presented in 1972 [61] is often mistakenly drawn into the discussion of transitional fossils. [62] This theory, however, pertains only to well-documented transitions within taxa or between closely related taxa over a geologically short period of time.
Gould's most significant contribution to evolutionary biology was the theory of punctuated equilibrium [2] developed with Niles Eldredge in 1972. [3] The theory proposes that most evolution is characterized by long periods of evolutionary stability, infrequently punctuated by swift periods of branching speciation.
The Bak–Sneppen model is a simple model of co-evolution between interacting species. It was developed to show how self-organized criticality may explain key features of the fossil record, such as the distribution of sizes of extinction events and the phenomenon of punctuated equilibrium. It is named after Per Bak and Kim Sneppen.
Punctuated gradualism is considered to be a variation of these models, lying somewhere in between the phyletic gradualism model and the punctuated equilibrium model. It states that speciation is not needed for a lineage to rapidly evolve from one equilibrium to another but may show rapid transitions between long-stable states.
In apparent confirmation of this punctuated equilibrium view of evolution, the fossil record of an evolutionary progression typically consists of species that suddenly appear, and ultimately disappear, hundreds of thousands or millions of years later, without any change in external appearance.
The modern synthesis was the widely accepted early-20th-century synthesis reconciling Charles Darwin's theory of evolution by natural selection and Gregor Mendel's theory of genetics in a joint mathematical framework. It established evolution as biology's central paradigm.