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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 Per Bak (8 December 1948 – 16 October 2002) was a Danish theoretical physicist who coauthored the 1987 academic paper that coined the term "self-organized criticality." Life and work After receiving his Ph.D. from the Technical University of ...
and Kim Sneppen. The model dynamics repeatedly eliminates the least adapted species and mutates it and its neighbors to recreate the interaction between species. A comprehensive study of the details of this model can be found i
''Phys. Rev. E'' 53, 414–443 (1996)
A solvable version of the model has been proposed i
''Phys. Rev. Lett.'' 76, 348–351 (1996)
whic
shows
that the dynamics evolves sub-diffusively, driven by a long-range memory. An evolutionary local search heuristic based on the Bak–Sneppen model, called
extremal optimization Extremal optimization (EO) is an optimization heuristic inspired by the Bak–Sneppen model of self-organized criticality from the field of statistical physics. This heuristic was designed initially to address combinatorial optimization problems su ...
, has been introduced in The Bak–Sneppen model has been applied to the theory of scientific progress.


Description

We consider ''N'' species, which are associated with a fitness factor ''f''(''i''). They are indexed by integers ''i'' around a ring. The algorithm consists in choosing the least fit species, and then replacing it and its two closest neighbors (previous and next integer) by new species, with a new random fitness. After a long run there will be a minimum required fitness, below which species don't survive. These "long-run" events are referred to as avalanches, and the model proceeds through these avalanches until it reaches a state of relative stability where all species' fitness are above a certain threshold.Wei1, Li; Yang, Luo; YuanFang, Wang & AiPing, Cai. "A mean-field Bak-Sneppen model with varying interaction strength". Chinese Science Bulletin, 2011, p. 3639.


See also

* Evolutionary biology


References

* * * * {{DEFAULTSORT:Bak-Sneppen model Chaotic maps Evolutionary biology Self-organization Mathematical and theoretical biology